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Research ArticleDecember 8, 2020

Lytic Polysaccharide Monooxygenase-Assisted Preparation of Oxidized-Cellulose Nanocrystals with a High Carboxyl Content from the Tunic of Marine Invertebrate Ciona intestinalis
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Anthi Karnaouri
Anthi Karnaouri
Biochemical Process Engineering, Chemical Engineering, Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, Luleå 97187, Sweden
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Blanca Jalvo
Blanca Jalvo
Department of Materials and Environmental Chemistry, Stockholm University, Stockholm 10691, Sweden
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Philipp Moritz
Philipp Moritz
Clausthal Centre of Material Technology, Clausthal University of Technology, Clausthal-Zellerfeld 38678, Germany
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http://orcid.org/0000-0002-7582-101X
Leonidas Matsakas
Leonidas Matsakas
Biochemical Process Engineering, Chemical Engineering, Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, Luleå 97187, Sweden
More by Leonidas Matsakas
http://orcid.org/0000-0002-3687-6173
Ulrika Rova
Ulrika Rova
Biochemical Process Engineering, Chemical Engineering, Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, Luleå 97187, Sweden
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Oliver Höfft
Oliver Höfft
Institute of Electrochemistry, Clausthal University of Technology, Clausthal-Zellerfeld 38678, Germany
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http://orcid.org/0000-0002-1313-3166
Georgia Sourkouni
Georgia Sourkouni
Clausthal Centre of Material Technology, Clausthal University of Technology, Clausthal-Zellerfeld 38678, Germany
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Wolfgang Maus-Friedrichs
Wolfgang Maus-Friedrichs
Clausthal Centre of Material Technology, Clausthal University of Technology, Clausthal-Zellerfeld 38678, Germany
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Aji P. Mathew*
Aji P. Mathew
Department of Materials and Environmental Chemistry, Stockholm University, Stockholm 10691, Sweden
*Email: [email protected]. Tel.:+46 (0) 8161256.
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http://orcid.org/0000-0001-8909-3554
Paul Christakopoulos*
Paul Christakopoulos
Biochemical Process Engineering, Chemical Engineering, Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, Luleå 97187, Sweden
*Email: [email protected]. Tel.: +46 (0) 920 492510.
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http://orcid.org/0000-0003-0079-5950

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ACS Sustainable Chemistry & Engineering

Cite this: ACS Sustainable Chem. Eng. 2020, 8, 50, 18400–18412

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https://doi.org/10.1021/acssuschemeng.0c05036

Published December 8, 2020

Abstract

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The tunicate species Ciona intestinalis is a fast-growing marine invertebrate animal that contains cellulose in its outer part—the tunic. The high crystallinity and microfibril aspect ratio of tunicate cellulose make it an excellent starting material for the isolation of nanocellulose. In the present work, tunic from C. intestinalis was subjected to organosolv pretreatment followed by bleaching and acid-hydrolysis steps for the isolation of nanocrystals. Applying an intermediate enzymatic treatment step with a lytic polysaccharide monooxygenase (LPMO) from the thermophilic fungus Thermothelomyces thermophila was proved to facilitate the isolation of nanocellulose and to improve the overall process yield, even when the bleaching step was omitted. LPMOs are able to oxidatively cleave the glycosidic bonds of a polysaccharide substrate, either at the C1 and/or C4 position, with the former leading to introduction of carboxylate moieties. X-ray photoelectron spectroscopy analysis showed a significant increase in the atomic percentage of the C═O/O–C–O and O–C═O bonds upon the addition of LPMO, while the obtained nanocrystals exhibited higher thermal stability compared to the untreated ones. Moreover, an enzymatic post-treatment with LPMOs was performed to additionally functionalize the cellulose nanocrystals. Our results demonstrate that LPMOs are promising candidates for the enzymatic modification of cellulose fibers, including the preparation of oxidized-nanocellulose, and offer great perspectives for the production of novel biobased nanomaterials.

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Synopsis

Organosolv fractionation combined with enzymatic treatment with LPMOs allows for the isolation of nanocrystals with a high carboxyl content from Ciona intestinalis tunic.

Introduction

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The decrease of oil-based resources prompts the use of biomass as a feedstock to produce renewable materials, which are expected to be environmentally friendly and offer improved properties, such as biodegradability and enhanced biocompatibility. Cellulose is a natural renewable, biodegradable, and biocompatible polymer with abundant availability, which makes it a very promising substrate for numerous applications. Being a hierarchical material, cellulose can be used for the preparation of two types of biobased nanomaterials viz. cellulose nanofibrils and cellulose nanocrystals (CNCs), each one with distinct properties regarding their shape, size, and morphology. (1) Both these nanoparticles have found application in various fields, including polymer reinforcement, production of antimicrobial and medical materials, biosensors, hydrogels, drilling fluids, and drug delivery systems. (2−4) Cellulose nanofibrils are processed by mechanical treatment, including homogenization or grinding with or without other pretreatment steps that provide lateral cleavage of cellulose fibers into nanofibrils with diameters less than 10 nm and lengths in the micron scale. (5) The isolation of cellulose into highly crystalline nanoscale materials, namely, CNCs, requires chemical treatments such as acid hydrolysis to remove the amorphous regions in the cellulose chains and yield fibrils that typically have diameter < 10 nm and lengths in the nanometer range, for example, 150–300 nm for wood-based nanocrystals. (6)

The isolation of cellulose into CNCs has become a major research focus because of their attractive combinations of physicochemical characteristics, such as high crystallinity and good processability, as well as high specific strength and modulus, biocompatibility, and biodegradability, among others. (5,7) The dimensions and the crystallinity of these nanocrystals depend on the origin of the cellulose fibers as well as the procedure employed to obtain them because variations in the CNC extraction process lead mainly to different CNC properties. (8,9) Wood and annual plants are the commonly used natural resources for cellulose and nanoscale cellulose. Although cellulose can be produced from the cell wall of certain algae and bacteria, tunicates, which live in the oceans, are the only known animal species that produces cellulose in the outer tissues. Tunic, the mantle of these animals, contains cellulose of high crystallinity (80–90%) and a high aspect ratio, called tunicin, which offers excellent polymer reinforcement properties at very low concentrations, thus indicating its excellent chemical and material applications. (10) Tunicin nanocrystals (TNCs), which are usually isolated through sulphuric acid hydrolysis and are functionalized with -HSO₃ groups that provide anionic surface charges, (11) are well known to be much longer than those of plant origin, exist predominantly in the I_β polymorph, and have a very large aspect ratio, high crystallinity, and a high specific surface area. (12) Nanocrystals from tunicates belonging to species Styela clava and Halocynthia roretzi and nanofibrils from Ciona intestinalis have been successfully isolated and characterized, (12−14) while Mathew et al. have demonstrated the efficient reinforcement of TNCs in biopolymer matrices as plasticized starch. (11,15)

Apart from mechanical and chemical processes, enzyme-mediated pretreatment approaches in aqueous environments have received increasing attention for the production of cellulose nanofibrils and nanocrystals partially because of the high substrate specificity of enzymes. (16) Cellulases, mainly endoglucanases and exoglucanases, as well as xylanases, have been shown to play a key role in improving cellulose nanofiber production by removing the amorphous regions, thus facilitating refining and fibrillation. (17,18) Accessory enzymes such as lytic polysaccharide monooxygenases (LPMOs) can increase the hydrolytic performance of cellulase cocktails by facilitating the accessibility of the enzymes to the cellulosic component. (19−21) LPMOs represent a powerful class of enzymes that are able to oxidatively cleave cellulose and other recalcitrant polysaccharides, and they possess a type II copper active center coordinated by a histidine brace. (22−24) Apart from boosting the production of fermentable sugars, LPMOs have been recently reported to be able to introduce carboxyl groups to the substrate, (20,25) thus increasing the electrostatic repulsion of cellulose fibers and, in this way, promoting the fibrillation process toward the formation of cellulose nanofibrils through decreasing the energy requirements of mechanical treatment. (26−28) In a similar way, LPMOs could partially or entirely substitute the need for harsh chemical treatments that lead to fiber modification and swelling, such as bleaching.

The ability of LPMOs to introduce carboxylate moieties on the surface of cellulose makes them promising candidates as biocatalysts for the biofunctionalization of nanocellulose. Oxidized nanocelluloses have gained much attention not only in the biomedical field because of their antimicrobial properties (29) but also as scaffolds for the grafting of various molecules to produce modified materials, (30) as there is increasing interest in replacing petrol-based or synthetic polymers by sustainable, biobased materials. Until now, a chemoenzymatic modification process using laccase as the biocatalyst and TEMPO as the enhancer (laccase–TEMPO system) is the only one that has been applied to introduce carbonyl and carboxyl groups at the C6 position. (31) A different mechanism of oxidation is employed by LPMOs because these catalysts are able to catalyze cleavage of the polysaccharide substrates by oxidation at the C1 and/or C4 position, yielding products with either an additional carboxyl group (lactonic acids) or gemdiols (hydrated form of corresponding 4-ketolaldoses), respectively. (32) It has been recently reported that an AA11 LPMO from Fusarium fujikuroi is able to catalyze the introduction of carboxyl groups on α-chitin, without affecting significantly the crystallinity of the fibers. (33) In a similar way, LPMOs can be utilized for the modification of cellulose surface properties toward the production of oxidized materials with defined properties. (18,28,34)

In the current study, tunic from the marine invertebrate C. intestinalis was utilized, for the first time, as a feedstock for the preparation of CNCs with a high carboxyl content. The available amount of C. intestinalis cellulose is approximately 560,000 tons (dry weight) at full production in Sweden. Tunicates have an extremely high growth capacity, and they are predicted to become much more common in the coming years as a result of climate change and marine eutrophication; therefore, exploitation of their potential for novel applications sounds promising. To achieve the goal of nanocrystal production, we employed a strategy based on organosolv (OS) pretreatment for the initial fractionation of the material and the recovery of a cellulose-rich fraction, combined with the use of LPMOs as an additional enzymatic treatment step, together with a modification of the widely used acid hydrolysis extraction, to introduce carboxyl groups on the polysaccharide substrates and prepare oxidized TNCs. A post-treatment with LPMOs was also assessed for the modification of the isolated TNCs. Our results demonstrate that pretreatment with LPMOs improved the isolation of TNCs, even when the bleaching step was omitted, thus simplifying and reducing the costs of the extraction process, while post-treatment with LPMOs could further increase the carboxyl content and the negative surface charge of TNCs.

Experimental Section

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Preparation of the Tunic Material

OS Pretreatment of Tunic

The whole tunic from the marine invertebrate C. intestinalis, harvested in South Sweden, was provided by Marine Feed Sweden AB. It was thoroughly washed with fresh water, air-dried in an oven (80 °C), and used as the raw material. OS pretreatment took place in a high-pressure hydrothermal reactor, as previously described. (35) A suspension of biomass and aqueous EtOH solution (60% v/v), with a liquid to solid ratio of 10, was treated at 175 °C for 60 min and subsequently cooled down below 40 °C. After pretreatment, the solid fraction was separated from the pretreatment liquor by vacuum filtration, washed with fresh aqueous EtOH solution (60% v/v), dried in an oven at 50 °C, and stored at room temperature. Structural carbohydrate analysis of untreated and pretreated solids was conducted following the NREL protocol. (36) The monomeric sugars produced were quantified by ion-exchange chromatography using an Aminex HPX-87 N column with a microguard column at 85 °C (Bio-Rad Laboratories, Hercules, CA, USA), specified for the analysis of samples with high salinity, using ultrapure H₂O (Type I) at a flow rate of 0.6 mL/min as the mobile phase. Inorganic ash and protein contents were determined according to the procedures previously described. (35)

Enzymatic Treatment of Tunic and Analysis of the Product Profile

For the enzymatic pretreatment of the tunic, MtLPMO9H (XP_003661787 and MYCTH_46583) from Thermothelomyces thermophila (previously known as Myceliophthora thermophila) was used. The enzyme was heterologously produced in Pichia pastoris and purified to its homogeneity, as previously described. (37) This LPMO exhibits a double C1/C4-oxidizing activity, although it is the C1-oxidizing effect that is the most important in the context of this study. The enzymatic treatment of tunic took place at 50 mM sodium acetate, pH 6.0, and 50 °C, for 18 h. Ascorbic acid was used as the electron donor at a final concentration of 5 mM. The initial solid loading was 4.5% w/v, and the enzyme loading was 30 mg/g of substrate. At the end of the enzymatic reaction, the tunic was recovered after centrifugation and was washed extensively with distilled H₂O and Triton-X (0.1% w/v) to remove the residual enzyme that has been bound to the biomass. The supernatant was analyzed for the oxidized products of the MtLPMO activity on tunic. The soluble oxidized products of MtLPMO were first detected by high-performance anion exchange chromatography (HPAEC), using an ICS 5000SP system (Dionex, Thermo Fisher Scientific Inc.), as previously described. (37) Protein concentration was identified by the Lowry method, using the Folin phenol reagent. (38)

To further identify the reaction products, liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI MS/MS) analysis was used. Prior to the analysis, 20 μL of each sample were diluted with 20 μL 0.1% v/v trifluoroacetic acid (TFA) and applied to a C-18 Ziptip packed with 15 μL graphitized carbon, which was pre-equilibrated with 3 × 25 μL 90% v/v acetonitrile (AcCN) containing 0.5% v/v TFA and 3 × 25 μL 0.5% v/v TFA. The Ziptip was washed with an additional 3 × 25 μL 0.5% v/v TFA after applying samples. The oxidized samples were eluted with 3 × 25 μL 40% v/v AcCN containing 0.5% v/v TFA. The eluent was dried in SpeedVac and reconstituted with 10 μL H₂O. To reduce the samples, 20 μL of each sample were incubated with 20 μL of 1 M NaBH₄ and 20 mM NaOH at 50 °C overnight. Salts were removed from the samples as described previously. (39) 3 μL of each sample was applied to analysis. The sugars were separated on a column (10 cm × 250 μm) packed in-house with 5 μm porous graphite particles (Hypercarb, Thermo-Hypersil, Runcorn, UK) and eluted with an acetonitrile gradient (Buffer A, 10 mM ammonium bicarbonate; Buffer B, 10 mM ammonium bicarbonate in 80% v/v AcCN). The gradient (0–45% Buffer B) was eluted for 46 min followed by a washing step with 100% Buffer B and equilibrated with Buffer A for the next 24 min. The samples were analyzed in both negative and positive-ion modes on an LTQ linear ion trap mass spectrometer (Thermo Electron, San José, CA), with an IonMax standard electrospray ionization source equipped with a stainless-steel needle kept at −3.5 kV. Compressed air was used as the nebulizer gas. The heated capillary was kept at 270 °C, and the capillary voltage was −50 kV. Full scan (m/z 380–2000, two microscans, maximum 100 ms, and a target value of 30,000) was performed followed by data-dependent MS² scans (two microscans, maximum 100 ms, and a target value of 10,000) with a normalized collision energy of 35%, an isolation window of 2.5 units, activation q = 0.25, and an activation time of 30 ms. The threshold for MS² was set to 300 counts. Data acquisition and processing were conducted with Xcalibur software (Version 2.0.7).

Isolation of TNCs

The TNC suspension was prepared by sulfuric acid hydrolysis following a modification of the process, as previously reported. (15) The aqueous tunicate suspension was mixed with H₂SO₄ to reach a final acid/H₂O concentration of 55 wt % at 70 °C under vigorous stirring. The hydrolysis was quenched by adding excess of distilled water after 30 min and allowed to cool down to room temperature. The suspension was successively centrifuged at 5000 rpm for 15 min at 4 °C to concentrate the CNCs and to remove the excess of aqueous acid. The isolated nanocrystals were rinsed and dialyzed in distilled H₂O until pH 4.5 was reached. The suspension was sonicated using a Qsonica Q500, 500-watt Sonicator at 75% output for 5 min.

In the case of those samples that were subjected to the additional bleaching step prior to sulphuric acid hydrolysis, a 5 wt % KOH solution was added to the samples, and the mixture was boiled under stirring for 6 h to swell the fibers, facilitate the infiltration of the bleaching solution, and lead to the removal of the residual cellulose-bound protein fraction and other tunic compounds. The final solution was extensively washed with distilled H₂O and was subsequently bleached upon addition of 0.19 M sodium chlorite into 0.3 M sodium acetate buffer, at 80 °C for 6 h, under agitation. The samples were washed with distilled H₂O, and then, a 5 wt % KOH solution was added, and the mixture was incubated at room temperature for 24 h. The samples were washed with distilled H₂O, and the final product was centrifuged for 15 min at 10000 rpm (15,344 xg) at 4 °C and resuspended in distilled H₂O. This process was repeated twice, and the TNC recovery yield was determined as previously described by Bondeson et al. (40) Briefly, recovery yield was calculated as the % of the initial weight of TNCs after hydrolysis. Approximately 1/4 of the total volume was freeze-dried and compared to the initial weight. Isolated TNCs were characterized as described below.

LPMO Post-treatment of TNCs

To examine whether enzymatic post-treatment could further increase the carboxyl content of isolated TNCs, an additional incubation with MtLPMO for 8 h took place. The initial concentration of TNCs was 0.5 wt %, and the enzyme loading was 10 mg/g of substrate. All other reaction conditions (buffer system, time, and agitation), as well as the TNC recovery and characterization process, were the same as those followed for TNCs prior to LPMO post-treatment.

Characterization of TNCs

Morphology and Size

Topographical surface images were captured using an atomic force microscope (Veeco Multimode V, USA) operating in tapping mode. For the analysis, prior to examination, a droplet of diluted suspension of the sample was deposited on a carbon microgrid and was allowed to dry. The diameter measurements were performed by employing the Nanoscope V software and analyzing the height images. The structure of the nanocrystals obtained was observed using a scanning electron microscopy (SEM) JEOL JSM-7000F instrument with an accelerating voltage of 3 kV. The samples were sputter-coated with a thin layer of gold for 80 s before SEM visualization. The particle length of the nanocrystals and the surface charge, namely, the zeta potential (ζ-potential) value of the TNC suspensions, were determined using dynamic light scattering (DLS) and electrophoretic light scattering in a Zetasizer Nano ZS (Malvern Instruments, Malvern, UK) apparatus. HCl and NaOH were used to adjust the pH to the required value (pH 7.0).

Thermal Analysis

The thermal behavior of the nanocrystals was assessed by thermogravimetric analysis (TGA), using TA Instruments Discovery thermal analyzer, to measure the mass transformation as a function of temperature, for an interval of 30–600 °C, at a heating rate of 5 °C/min. The samples were exposed to air gas at a flow rate of 20 mL/min. The reported values for each sample represent the average of three different measurements.

X-ray Photoelectron Spectroscopy (XPS) Analysis

For XPS measurements, 50 μL of diluted TNC suspension were deposited on a gold substrate and allowed to dry. The freshly prepared samples were analyzed by XPS in an ultrahigh vacuum chamber, with a base pressure below 5 · 10^–10 mbar. The detailed apparatus setup was described previously. (41,42) All samples were examined once, whereby XPS has a general detection limit of 0.1 at % and a measurement accuracy of 10%. (43) For MgKα X-ray generation, a commercial X-ray source (RS40B1, Prevac, Rogów, Poland) was used, and the X-rays hit the surface under an angle of 80° to the surface normal. The emitted photoelectrons were detected using a hemispheric analyzer (type Leybold EA10/100) under an angle of 10° to the surface normal. The pass energy for the analyzer was kept constant at 80 eV for survey spectra and at 40 eV for detailed spectra. All XP spectra are displayed as a function of binding energy with respect to the Fermi level. Because of a constant shift in all components assigned to the cellulose, XP spectra have been charge-corrected using the aliphatic C–C binding at 285.0 eV as a reference. For quantitative XPS analysis, a linear background subtraction for the photoelectron peaks was employed. The peak components were deconvoluted by Voigt-type profiles with CasaXPS software (version 2.3.16 Pre-rel 1.4, CasaXPS Ltd., Teignmouth, United Kingdom).

X-ray Diffraction (XRD) Analysis

The crystallinity index (CrI) of the tunicate CNCs was determined by XRD using a PANalytical Empyrean X-ray diffractometer, with a smallest increment of 0.0001° and angular reproducibility <0.0002°, equipped with a PixCel3D detector and a graphite monochromator. CuKÜ1 radiation with λ = 1.540598 at 45 kV and 40 mA was used in the 2θ range of 5–90° at a scanning speed of 0.026°/s. CrI was assessed by the peak height method suggested by Segal. (44)

Evaluation of the TNC Effect on Bacterial Growth

The ability of isolated TNCs to inhibit the growth of Bacillus subtilis subsp. spizizenii (DSM 347) and Escherichia coli (DSM 1103) was assayed by the growth curve method. Exponential-phase cultures were grown overnight in Casein Soya and Luria-Bertani liquid broth for B. subtilis and E. coli, respectively. Cultures were subsequently diluted to an optical density at 600 nm (OD₆₀₀) of 0.0138 (10⁸ cells/mL) and placed in 15 mL sterile tubes containing the appropriate nutrient broth supplemented with the different TNC samples at a final concentration of 0.25% w/v. The bacterial growth in nutrient broth in the absence of TNCs was used as a positive control, while the negative control consisted of bacteria incubated in pure TNC solution in distilled H₂O. Nutrient broth was used as a blank. Cultures were incubated at 37 °C, for E. coli, and 30 °C, for B. subtilis for 24 h, under agitation (160 rpm). Samples were taken at different time intervals (2, 4, 6, 8, 18, 20, and 24 h), and the growth was monitored spectrophotometrically by measuring the OD₆₀₀. Triplicate experiments were carried out for each bacterial culture.

Results and Discussion

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Pretreatment Steps for the Preparation of TNCs

In the present study, the cellulose-rich tunic of C. intestinalis was employed as a starting material for the isolation of nanocrystals. TNCs have been obtained after subjecting biomass to a combined process using two novel and independent pretreatment methods, either followed or not by bleaching, prior to the acid hydrolysis step, as summarized in Figure 1. These methods included: (i) an initial OS pretreatment method, by employing a low-toxic aqueous ethanol solution, which has been previously reported to be very efficient for the fractionation of tunic and the removal of proteins and lipids (33) and (ii) an additional enzymatic treatment with LPMO that has been demonstrated to promote fibrillation and facilitate the isolation of cellulose nanofibrils from other feedstocks, such as cotton linters, (34) birchwood Kraft pulp, (27) and spruce biomass. (28) The tunicin without any pretreatment was also processed in parallel and used as the control.

Figure 1. Flow diagram of the experimental process.

According to the results from our previous study, (35) after the OS pretreatment of tunic, the cellulose, protein, and ash contents of the material were 48.5, 10.1, and 32.3 wt %, respectively. The results show selective recovery of cellulose in the solids (the cellulose matrix remains intact) and solubilization of protein and ash, which underline the suitability of this process as an initial step for the isolation of TNCs. OS was selected in our case not only for its ability to achieve efficient fractionation of different biomass feedstocks (35,45,46) but also because it has been reported to promote swelling of cellulose fibrils (47) without decreasing the crystallinity. (48)

Prior to the isolation of TNCs, incubation of the samples with a fungal MtLPMO was employed as a second pretreatment step. The soluble products of the LPMO reaction on the OS-pretreated material were analyzed to verify the activity of the enzyme on the substrate. Control reactions in the absence of LPMOs with 5 mM ascorbic acid and copper equimolar to the LPMO added were also performed. HPAEC data are depicted in Figure 2 and show the presence of nonoxidized and oxidized sugars. MtLPMO belongs to the auxiliary activity 9 (AA9) family of the CAZy database (http://www.cazy.org/AA9.html) (49) and exhibits a double regioselectivity mode of action; (37) the enzyme releases a mix of C1, C4, and C1/C4 double oxidized oligosaccharides from OS-pretreated tunic. LC-ESI MS/MS analysis (Figure S1, Supporting Information) occurred based on reports in the literature, (50) and it reveals the formation of C1 and C4-oxidized products in hydrated form (aldonic acids and gemdiols) with a DP = 2–5, in nonhydrated form (lactones and 4-ketoaldoses) with a DP = 3–6, as well as nonoxidized cello-oligosaccharides with varying size (DP = 3–8), as shown in Table 1. Traces of oxidized pentose oligosaccharides were also detected, which probably originate from the activity of MtLPMO on sulfated xylans that have been observed in tunic of C. intestinalis. (51) After incubation with MtLPMO, the solubilization of the material was <3 wt %, verifying that the soluble products represented only a small fraction of the initial substrate; this is in accordance with the already known mode of action of LPMOs, being reported to create nicking points on the surface of fibers and introduce carboxyl groups on the crystalline areas of cellulose. (52) The C1-oxidative activity of MtLPMO on the OS-pretreated tunic sample makes it a promising candidate biocatalyst to facilitate the isolation of TNCs. The tunicin of invertebrates has been shown to form a very dense structure of bundled fibrils embedded in the tunic matrix. (10) The increase of surface charge upon addition of LPMOs might enable the disruption of this rigid structure.

Figure 2. HPAEC chromatograph of soluble products detected after activity of MtLPMO on OS-pretreated tunic. The profile of the products reveals a mixed C1/C4-oxidizing activity. The products of blank reactions in the absence of enzyme (blank reaction 1, without enzyme, only ascorbic acid, and copper equivalent to LPMOs added) and electron donor (blank reaction 2 and only MtLPMO) are also depicted.

Table 1. Structure of Oxidized and Nonoxidized Products Detected in the Reaction Medium after the Action of MtLPMO on OS-Pretreated Tunic Biomass as the Substrate

[M + Na]	structure of oligosaccharides (DP)
C1 and C4-oxidized products in hydrated form (aldonic acids and gemdiols)
381	-Glcβ1-4Glc- (DP2)
543	-Glcβ1-4Glcβ1-4Glc- (DP3)
705	-Glcβ1-4Glcβ1-4Glcβ1-4Glc- (DP4)
867	-Glcβ1-4Glcβ1-4Glcβ1-4Glcβ1-4Glc- (DP5)
C1 and C4-oxidized products in nonhydrated form (lactones and 4-ketoaldoses)
525	-Glcβ1-4Glcβ1-4Glc- (DP3)
687	-Glcβ1-4Glcβ1-4Glcβ1-4Glc (DP4)
849	-Glcβ1-4Glcβ1-4Glcβ1-4Glcβ1-4Glc (DP5)
1011	-Glcβ1-4Glcβ1-4Glcβ1-4Glcβ1-4Glcβ1-4Glc (DP6)
nonoxidized products
527	Glcβ1-4Glcβ1-4Glc (DP3)
689	Glcβ1-4Glcβ1-4Glcβ1-4Glc (DP4)
851	Glcβ1-4Glcβ1-4Glcβ1-4Glcβ1-4Glc (DP5)
1013	Glcβ1-4Glcβ1-4Glcβ1-4Glcβ1-4Glcβ1-4Glc (DP6)
1175	Glcβ1-4Glcβ1-4Glcβ1-4Glcβ1-4Glcβ1-4Glcβ1-4Glc (DP7)
1337	Glcβ1-4Glcβ1-4Glcβ1-4Glcβ1-4Glcβ1-4Glcβ1-4Glcβ1-4Glc (DP8)
437	Xylβ1-4Xylβ1-4Xyl (DP3)
569	Xyl1-4Xylβ1-4Xylβ1-4Xyl (DP4)
701	Xyl1-4Xylβ1-4Xylβ1-4Xylβ1-4Xyl (DP5)
833	Xyl1-4Xyl1-4Xylβ1-4Xylβ1-4Xylβ1-4Xyl (DP6)

Isolation, Recovery, and Properties of Isolated TNCs after Pretreatment

Untreated (Sample A), OS-pretreated (Sample B), and OS/LPMO-pretreated (Sample C) materials were all subjected to acid hydrolysis, in either the presence (Samples A, B, and C) or the absence (Samples B_w/o and C_w/o) of an additional intermediate bleaching step. Upon addition of sulphuric acid, disruption and hydrolysis of amorphous regions surrounding the embedded parts within the cellulose microfibrils occurred, leaving the microcrystalline segments intact. The recovery yield, final concentration of the TNC suspension, and ζ-potential of the TNCs isolated are summarized in Table 2, while the particle length is described in Table S1, Supporting information.

Table 2. Recovery Yield, % Wt. Concentration, and ζ-Potential Values of the TNCs Isolated from Tunic Biomass by Different Pretreatment Methods^a.

	isolated TNCs after pretreatment
sample	recovery yield (wt %)	concentration (wt %)	ζ-potential, pH 7 (mV)
untreated material (A)	63.3	0.48	–26.0 ± 2.3
OS-pretreated (B)	72.9	0.55	–22.9 ± 1.2
OS-pretreated w/o bleaching (B_w/o)	26.8	0.24	–16 ± 0.7
OS/LPMO-pretreated (C)	91.2	0.54	–22.1 ± 1.2
OS/LPMO-pretreated w/o bleaching (C_w/o)	85.1	0.52	–27.8 ± 0.8

^{^a}

The letters in the left column refer to the corresponding pictures of Figure 1

TNCs were successfully isolated with high recovery yields (>60 wt %) from almost all biomass samples, as observed at Table 2; the only exception was observed when OS constituted the only treatment that had been applied prior to acid hydrolysis (Sample B_w/o), where the recovery yield was very low (26.8 wt %). Bleaching step enabled the removal of inorganic ash content and further removal of the residual protein left after OS pretreatment. Because the amount of protein was low (10.1 wt %) as mentioned above, it is possible that the enhancing effect of bleaching in non-LPMO treated pulps (Samples A, B) occurred because of the removal of inorganic ash. The low nanocrystal yield indicates that the isolation of nanocrystals in the presence of inorganic structures is hampered. This can be possibly attributed to the presence of calcium in these structures, which was further confirmed by scanning electron microscopy-energy-dispersive spectrometry (SEM-EDS) analysis (Figure S2C, Supporting information); these results are also in agreement with previously reported data from ash analysis of the OS-pretreated material, which shows the presence of calcium at a concentration of 33.1 mg/g. (35)

OS pretreatment enabled fractionation of tunic biomass; however, although in small amounts, the presence of protein, as well as the inorganic ash, negatively affected the TNC isolation process in the absence of the bleaching step. In the case of LPMO pretreatment though, the enzyme facilitated the disruption of cellulose fibrils, therefore promoting the isolation of TNCs. Even when omitting the bleaching step, the OS/LPMO-pretreated material (Sample C_w/o) led to 85.1 wt % recovery yield, whereas the corresponding bleached material showed even higher recovery (91.2 wt %). Our results regarding the LPMO efficiency in facilitating fibril separation are in accordance with those previously reported in the literature; introducing a pretreatment step with a fungal PaLPMO9E from Podospora anserina enabled further processing of birchwood fibers for the production of cellulose nanofibrils, (26) while softwood kraft cellulose was more prone to mechanical fibrillation after activity of PaLPMO9H from the same fungus. (27) The great potential of LPMOs as environmentally friendly catalysts for the preparation of cellulose nanofibers from spruce is also highlighted in the pioneered work by Koskela et al. (28) Apart from reducing the use of harsh chemicals, the ability to isolate TNCs in the absence of the bleaching step may offer another additional advantage; because bleaching leads to removal of inorganic compounds, such as calcium and silica, omitting this step leads to production of TNCs decorated with inorganic residues, which offer great potential for further applications, such as in the preparation of hydrogels and hybrid biomaterials through cross-linking. (53,54)

DLS Measurements and Determination of ζ-Potential

ζ-Potential is used to estimate the electrostatic repulsion between particles and thus to determine the colloidal stability of the TNCs. The ζ-potential is a function of the surface charge density of the material and the particle size. As shown in Table 2, with the exception of the OS-pretreated material w/o bleaching (Sample B_w/o), all TNCs exhibit a ζ-potential absolute value over 20 mV, which can be translated into stable colloidal suspensions. (55) In the absence of LPMO treatment (Samples A, B, and B_w/o), the results indicate that TNCs have electrically negative surface charge, which can be attributed to the presence of sulphate half-esters introduced during sulphuric acid hydrolysis. (56) In the case of the LPMO-pretreated Sample C_w/o, the ζ-potential value is slightly higher probably because of the addition of carboxylate moieties at the C1 position. As mentioned above and has been previously reported, (37)MtLPMO is able to perform both C1 and C4 oxidation, resulting in the formation of a carboxylic acid or a gemdiol, respectively. The presence of LPMO-introduced C1-carboxyl groups on the surface of the material generates electrostatic repulsion that hampers the aggregation of TNCs and increases the colloidal stability (57) by improving solubility and dispersion of the fibers. Similar results after LPMO treatment of the fibers are reported in other studies, (27,28,34) while Hu et al. managed to efficiently produce from softwood a self-stabilized suspension of nanofibers with a ζ-potential value of −60 mV upon the addition of AA9 together with cellulases. (18) Other types of oxidative treatment have been shown to increase the electrostatic repulsion of the subsequently isolated nanofibers; apart from the widely used TEMPO-oxidation, (58) and the combination of OS treatment in conjunction with a mild oxidative process has also been reported in the literature for the isolation of CNCs from Eucalyptus wood, where oxidative irradiation produced pulps with a higher absolute ζ-potential value. (59) Surprisingly, the absolute value of the ζ-potential upon LPMO treatment in the absence of bleaching (Sample C_w/o) was higher than that upon LPMO treatment with bleaching (Sample C_w/o). These results could probably reflect the effect of other compounds that remain in the structure in the absence of bleaching and affect the surface charge density of the material. To elucidate the effect of different pretreatment steps on the final composition and overall structure of the samples, further research is required.

Atomic Force Microscopy (AFM) Imaging and Measurement of the TNC Diameter

The structure and size of the TNCs were both analyzed by AFM (Figure 3A). AFM images obtained from diluted TNC suspensions show the presence of well-isolated nanoscale TNCs, except for the nanocrystals originating from the unbleached OS-pretreated material (Sample B_w/o), where residual structures are present, as verified by SEM-EDS analysis (Figure S2C, Supporting information) and discussed above. These structures are expected to originate from the inorganic ash in the biomass, which was not completely removed during the processing route followed. All the samples displayed a rodlike shape, as expected and reported before for TNCs, (10,11) with length ranging from 600 nm up to almost 1 μm. The images show that the TNCs from the unbleached OS/LPMO-pretreated material (Sample C_w/o) (Figure 3A-a) are more individualized compared to the other TNCs. This could be attributed to the presence of carboxyl groups introduced by LPMOs that, together with the sulphate groups on the surface of the nanocrystals because of acid hydrolysis, promote repulsive forces that keep the nanocrystals apart from each other. Because broadening effects may occur during scanning because of the tip geometry, the nanocrystal diameter was determined from the AFM height images by employing the Nanoscope V software. As a mean value of triplicates, the average diameter of TNCs is presented in Figure 3B. The diameter varies from 4.45 nm ± 1.07 to 26.08 nm ± 6.63, which corresponds to the OS/LPMO-pretreated material w/o bleaching (Figure 3A-e) and OS-pretreated material w/o bleaching (Figure 3A-c), respectively. Results from DLS analysis (Table S1, Supporting information) showed that LPMO-pretreatment did not affect the length of the TNCs produced (Samples C and C_w/o). On the contrary, the width was shown to be reduced, either in the absence (Sample C_w/o) or presence (Sample C) of the bleaching step, yielding more fine and thin nanocrystals. Our results are in accordance with those previously reported, (27,34) verifying the decrease of the nanocellulose diameter upon LPMO treatment as a result of fiber disruption induced by the enzyme oxidative activity.

Figure 3. (A) AFM images of TNCs isolated from the untreated material (A), OS-pretreated material (B), OS-pretreated material w/o bleaching (B_w/o), OS/LPMO-pretreated material (C), and OS/LPMO-pretreated material w/o bleaching (C_w/o). (B) TNC diameter measured with Nanoscope V software.

AFM characterization and recovery yield of isolated TNCs (Table 2 and Figure 3) showed that when the material is pretreated with LPMO, the bleaching step is not of pivotal importance to obtain nanocrystals (Sample C_w/o). LPMOs promote the liberation and disintegration of cellulose fibers and enhance the subsequent isolation of nanocrystals from tunic. TNCs after LPMO pretreatment are thinner, longer, and with higher electrically negative charge. As mentioned above, the samples obtained after MtLPMO treatment (Samples C and C_w/o) had an absolute ζ-potential value above 20 mV (Table 2), indicating that there is no agglomeration because of the sufficient mutual repulsion resulting in colloidal stability. Although the effect of LPMOs has been evaluated mainly toward the production of cellulose nanofibers, (26−28) both in the cases of preparing nanofibrils and nanocrystals, C1-oxidizing LPMOs seem to result in fiber delamination into thinner and shorter structures while introducing C1-carboxylate groups. The unique property of LPMO-catalyzed oxidation compared to other oxidation methods such as TEMPO is that, apart from the fiber repulsion because of these carboxylate groups that facilitate the colloidal stability of the final product, these enzymes also cause chain cleavage and disruption in the crystalline areas, which might also enhance the subsequent acid hydrolysis toward the isolation of CNCs.

Thermal Stability of TNCs

The data regarding the TGA of the TNCs are presented in Figure 4. The onset degradation and the peak degradation temperature as well as the wt % solid residue for each sample are summarized in Table 3.

Figure 4. TGA graphs of the TNCs isolated from tunic biomass after different treatments.

Table 3. Thermal Stability Data and CrI of the Isolated TNCs^a

	thermal stability parameters			CrI (%)
sample	onset temperature (T₀) (°C)	peak degradation temperature (T_max) (°C)	residue (%)	CrI (%)
untreated material (A)	167. ± 10.8	280.7 ± 11.4	1.4 ± 0.6	83
OS-pretreated (B)	220.6 ± 8.0	276.1 ± 24.0	36.1 ± 5.2	79
OS-pretreated w/o bleaching (B_w/o)	33.5 ± 5.6	290.6 ± 5.9	60.7 ± 3.0	N.D.
OS/LPMO-pretreated (C)	291.6 ± 15.9	326.3 ± 11.2	16.3 ± 10.3	81
OS/LPMO-pretreated w/o bleaching (C_w/o)	207.6 ± 12.4	265.3 ± 15.6	43.2 ± 2.6	76

^{^a}

Ν.D. not determined.

The TNCs isolated from the untreated material (Sample A) showed the typical TGA curve for CNCs obtained through sulphuric acid hydrolysis. (60−63) The average onset temperature of degradation of this sample was 167.72 ± 10.80 °C (Table 3), displaying one of the lowest thermal stabilities among all samples, following the TNCs isolated from the unbleached OS-pretreated material (Sample B_w/o). The introduction of the sulphate groups during the acid hydrolysis with sulphuric acid affects the thermal stability of the TNCs because of the dehydration reaction, thus rendering them more susceptible to degradation when the temperature increases. (62,63) Comparatively, TNCs isolated from the OS/LPMO-pretreated material (Sample C) presented the highest thermal stability (Table 3). Zhao et al. obtained similar results when they compared the effect of enzymatic hydrolysis to that of acid hydrolysis for the isolation of nanocrystals. (10) Our results suggest that the pretreated material, with the exception of the unbleached OS-pretreated one (Sample B_w/o), has undergone an effective “cleaning process” where the amount of sulphate groups on the nanocrystal surface has been decreased, thus leading to a higher thermal stability. The high percentage of residues observed in OS- and OS/LPMO-pretreated samples w/o bleaching (Samples B_w/o and C_w/o) is attributed to the inorganic ash, being the highest for the TNCs isolated from unbleached OS-pretreated tunicate biomass (Table 3). For these samples, the starting decomposition temperature has a lower value than for the corresponding bleached samples because of decomposition of proteins and other compounds that remain after the isolation process (proteins and lipids). The high thermal stability of the OS/LPMO-pretreated material (Sample C) is also related to the high crystallinity of the sample, as will be discussed below.

Determination of the CrI

Determination of the CrI of the samples is shown in Table 3. For the untreated material, the CrI (0.83) was similar to that previously mentioned in the literature for tunicate nanocrystals isolated after sulphuric acid hydrolysis (0.8) (12) and higher than that for nanocrystals isolated from wood biomass (0.60) (12,59) or bacterial cellulose (0.72). (12) Comparison of the results of the OS-pretreated material (Sample B) and OS/LPMO-pretreated material (Sample C) shows that addition of LPMOs slightly increases the crystallinity of the sample; this increase has been suggested to be related more to the C4-oxidation activity of LPMOs. (19) In another study, treatment with C1-oxidizing LPMOs did not significantly affect the CrI. (34) The OS/LPMO-pretreated material w/o bleaching (Sample C_w/o) exhibits lower crystallinity (0.76) than the corresponding sample after bleaching (0.81) possibly because of the residual compounds that remained after the isolation process.

XPS Analysis and Determination of the Carboxyl Content of TNCs

The XPS survey spectra for all samples (Figure S3, Supporting Information) present the two main characteristic peaks for cellulose, which can be assigned to carbon (285 eV) and oxygen (533 eV). (64) A more detailed analysis of the spectrum of the TNCs from the untreated material (Sample A) also reveals the presence of low amounts (<1 at. %) of sulfur with the S2p peak at 170 eV (Figure S4, Supporting information). This binding energy is characteristic of sulfate groups. (65) Pretreated samples, either after OS or OS/LPMO treatment (Samples B and C), contain only low amounts of SO₄^2– groups compared to the untreated one. This further confirms the results of TGA, where it was demonstrated that the pretreatment apparently “prevents” the introduction of sulphate groups on the substrate, thus increasing the thermal stability. In accordance with the ash analysis data that are reported above, some of the spectra also show very small proportions (<1 at. %) of Na, Si, and Ca, which, however, are not taken into account for an evaluation of the detailed spectra. The molybdenum peaks in the spectra are due to the metallic sample holder used for the analysis.

The detailed spectra of the C1s signal in Figure 5A show the oxidizing effect of the pretreatments. According to the XPS studies on nanocellulose by Mathew et al., (66) the following molecular species were used for the fitting of the C1s detailed peak (full width at half-maximum value, FWHM, is also provided):

1.	–C–C– / −C–H– (285.0 eV, FWHM 1.8 eV)
2.	–C–O– (287.0 eV, FWHM 1.6 eV)
3.	–C═O/O–C–O– (288.3 eV, FWHM 1.6 eV) and
4.	–O–C═O– (289.6 eV, FWHM 1.8 eV)

Figure 5. (A) XPS detailed spectra of the C 1 s region before (solid line) and after (dashed line) the LPMO post-treatment of the untreated material (A), OS-pretreated material (B), and OS/LPMO-pretreated material (C). (B) Stoichiometric amount of the molecular species.

A representative example for a fitted C1s detail peak can be found in Figure S5, Supporting Information. These species were adapted to all C1s detailed spectra, and Figure 5B shows the corresponding relative amount of each molecular species (functional group) present in the surface region. The peak shift to higher binding energies in the curves of the OS-pretreated material (Sample B), OS/LPMO-pretreated material (Sample C), and OS/LPMO-pretreated material w/o bleaching (Sample C_w/o) (Figure S6, Supporting information) indicates an increased proportion of oxidized −C═O/O–C═O bonds compared to the untreated material (Sample A), as a result of OS and LPMO treatment. Because the OS/LPMO-pretreated material w/o bleaching (Sample C_w/o) also exhibits this oxidation, it can be assumed that the LPMO-treatment could efficiently substitute the bleaching process toward the successful isolation of nanocellulose. However, it should be mentioned that a lower degree of oxidation could be observed for other unbleached samples prepared in the same manner. Further investigations have to be carried out here to find the reason for these differences. The presence of carboxyl groups on the surface results in strong electrostatic repulsion between TNCs in water, promoting the formation of CNCs, and offer great potential for further functionalization.

Evaluation of the TNC Effect on Bacterial Growth

Although oxidized cellulose can be used as a scaffold for grafting applications toward the development of materials with efficient antimicrobial properties, (67,68) the oxidized nanocellulose itself has shown an antibacterial effect, which is mainly bacteriostatic rather than bactericidal, and it is attributed to the presence of carboxylate groups. (69,70) Our aim was to study the effect of the oxidized nanocellulose prepared in this work on the growth of Gram-positive and Gram-negative bacteria, using B. subtilis and E. coli, respectively, as model organisms. To assess the bacteriostatic properties of nanocrystals from C. intestinalis tunic on the growth of the bacterial cultures, the optical density at 600 nm was measured at different time intervals after the incubation of the cultures with 0.25% w/v TNCs from the untreated (Sample A) and pretreated materials (Samples B, C, and C_w/o). As shown in Figure 6, growth rates of B. subtilis (Figure 6A) and E. coli (Figure 6B) were reduced upon addition of TNCs, compared to the corresponding cultures in the absence of TNCs. In general, the effect of the TNCs on B. subtilis resulted in a higher growth reduction than in E. coli, as expected, because Gram-positive bacteria are more sensitive to potential toxic agents than Gram-negative bacteria, because of the lack of the protective outer membrane in the former ones. (71,72) All bleached materials, including the unpretreated one, resulted in a similar reduction of the growth rate, whereas in the case of the OS/LPMO-pretreated material without bleaching (Sample C_w/o) such reduction was less pronounced. Τhis can be possibly attributed to the presence of inorganic compounds, such as calcium (Figure S2C, Supporting information) in the TNCs from unbleached biomass. Ca²⁺ has been identified as an intracellular signaling molecule in prokaryotes, related to optimal growth and morphology. (73,74) Our results demonstrate the bacteriostatic effect of TNCs on the two different bacterial strains tested, which could be partially hampered by the presence of Ca²⁺ when the bleaching step is omitted. Further studies need to be performed to elucidate and understand the decrease of the bacterial growth rate in the presence of TNCs and the possible effect of calcium ions.

Figure 6. Growth curve of *B. subtilis* and *E. coli* in the presence of 0.25% w/v TNCs: untreated material (A), OS-pretreated material (B), OS/LPMO-pretreated material (C), and OS/LPMO-pretreated material w/o bleaching (C_w/o).

LPMO Post-treatment of TNCs to Increase the Carboxyl Content

The isolated TNCs were subjected to a post-treatment with MtLPMO to evaluate whether it would be possible to further increase the carboxyl content. The effects of oxidative post-treatment of isolated nanocrystals with LPMOs have not been described earlier. TNCs from the OS-pretreated material w/o bleaching were not further processed, as this sample had a very low recovery yield and showed agglomeration. As depicted in Table 4, ζ-potential values turned more electrically negative after the LPMO post-treatment, confirming the extra charge introduction by the LPMO enzyme. This originates from the additional carboxyl groups added in the C1 position after the activity of LPMOs. (52) To exclude any possible surface modification caused by the addition of ascorbic acid and free copper, the isolated nanocrystals from the untreated sample (A) were treated with 5 mM ascorbic acid and 0.18 μM CuSO₄ which is equivalent to the amount of MtLPMO in the reaction. The samples were analyzed by XPS, and the results were compared to those upon addition of MtLPMO (Sample A_post-treated). The results depicted in Figure S7, Supporting information showed that the amount of carboxylate groups does not change after the treatment with ascorbic acid and free copper, corroborating the idea that the introduction of carboxylate groups, which is related to facilitating the isolation of nanocrystals, is attributed exclusively to the activity of LPMOs.

Table 4. Surface Charge and Crystallinity of TNCs after LPMO Post-treatment

sample	ζ-potential, pH 7 (mV)	CrI %
untreated material (A_post-treated)	–34.2 ± 1.7	63
OS-pretreated (B_post-treated)	–36.2 ± 2	76
OS/LPMO-pretreated (C_post-treated)	N.D.^a	75
OS/LPMO-pretreated w/o bleaching (C_{w/o - post-treated})	–35.9 ± 2.8	72

^{^a}

Ν.D. not determined.

All TNCs obtained after LPMO post-treatment had an absolute ζ-potential value above 30 mV, higher than those prior to incubation with LPMO. These results indicate that there is no agglomeration, which means that sufficient mutual repulsion led to colloidal stability. OS-pretreated TNCs (Sample B_post-treated) displayed the highest charge density, with a ζ-potential of −36.2 mV. Post-treatment of TNCs with LPMO led to a further increase of carbonyl and carboxyl groups, resulting in negative charge, while it does not affect the length of the TNCs.

Crystallinity of TNCs was decreased after the LPMO post-treatment probably because of the oxidative cleavage of the nanocrystals after the activity of LPMOs (Table 4). The CrI reduction was more profound in the case of the untreated material and the bleached OS/LPMO-pretreated material. This is probably attributed to the higher crystallinity of the samples prior to LPMO post-treatment because highly crystalline cellulose seems to be preferred by certain LPMOs. (75) The structure and size of the TNCs after the post-treatment with LPMOs were analyzed by AFM (Figure 7A). AFM images obtained from diluted post-treated TNC suspensions show, in general, lower aggregation between the nanocrystals and that the TNCs conserved their rodlike shape and length compared to the ones described before. As it was observed for the pretreated samples, the TNCs from the OS/LPMO post-treated material w/o bleaching (Sample (C_{w/o - post-treated}) are more individualized and thinner compared to the other post-treated TNCs. As it was commented for the pretreated nanocrystals, this could be attributed to the introduction of carboxyl groups introduced by the LPMO enzymatic post-treatment on the surface of the nanocrystals, together with the ones already being added during the pretreatment, thus promoting higher repulsive forces. The promotion of lateral cleavage of nanocrystals to single crystals also can be expected during this post-treatment step. The average diameter of LPMO post-treated TNCs is shown in Figure 7B, and it varies from 5.53 ± 1.07 nm, for the OS/LPMO-pretreated material w/o bleaching (Sample C_{w/o - post-treated}), to 10.22 ± 0.25 for the OS/LPMO-pretreated material (Sample C_post-treated).

Figure 7. (A) AFM images of the untreated material (A_post-treated), OS-pretreated material (B_post-treated), OS/LPMO-pretreated material (C_post-treated), and OS/LPMO-pretreated material w/o bleaching (C_{w/o - post-treated}) and (B) TNC diameter measurements after LPMO post-treatment, as identified by the Nanoscope V software.

To confirm the presence of additional functional carboxyl and carbonyl groups, TNCs after post-treatment with LPMOs were again investigated by XPS. The C1s detailed spectra were deconvolved, as described above, and are shown in Figure 5. The bars depicted in Figure 5B (shaded) present the relative amounts of functional groups after the LPMO post-treatment. The results show that the additional enzymatic treatment further increased the amount of −C═O/O–C═O bonds in all cases, confirming the results from the AFM and ζ-potential measurements. The oxidizing effect of LPMOs on TNCs that have already been enzymatically treated is lower. The XPS analysis of the OS/LPMO-pretreated material w/o bleaching showed very different results in repeated measurements; therefore, it is not listed in Figure 5. Further investigations must be carried out. Our results show the potential of LPMOs to achieve introduction of carboxyl groups on the surface of nanocrystals, which can theoretically occur in a controlled manner by applying different reaction times and/or enzyme concentrations. The above offers great perspectives for the design of one-pot enzymatic reactions with great selectivity for the production of functionalized nanomaterials.

Conclusions

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In the present work, a novel process that combines OS fractionation together with LPMO pretreatment is presented for the efficient isolation of CNCs from the C. intestinalis tunic. Our results show that TNCs are obtained in high yields, and they have high crystallinity, good thermal properties, and a high carboxyl content. MtLPMO is able to introduce both carboxylic and ketone groups to the substrate, as expected by the mixed C1/C4 oxidative activity of the enzyme. The presence of carboxylate ions on the surface results in strong electrostatic repulsion between TNCs in water, facilitating the nanocrystal formation even in the absence of the bleaching step. Moreover, for the first time, a post-enzymatic treatment with LPMOs is tested to additionally functionalize the CNCs, individualize the single crystals, and enhance the colloidal stability. This developed route demonstrates an energy and resource-efficient one-pot synthesis process that can be extended to other biomass substrates for isolating highly functional and negatively charged CNCs for various applications.

Supporting Information

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acssuschemeng.0c05036.

Mass spectrometry data of degradation products generated by MtLPMO, SEM figures, XPS spectra, relative amount of the molecular species, and particle length data for TNCs isolated following different treatments (PDF)

sc0c05036_si_001.pdf (1.3 MB)

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Author Information

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Corresponding Authors
- Aji P. Mathew - Department of Materials and Environmental Chemistry, Stockholm University, Stockholm 10691, Sweden; http://orcid.org/0000-0001-8909-3554; Email: [email protected]
- Paul Christakopoulos - Biochemical Process Engineering, Chemical Engineering, Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, Luleå 97187, Sweden; http://orcid.org/0000-0003-0079-5950; Email: [email protected]
Authors
- Anthi Karnaouri - Biochemical Process Engineering, Chemical Engineering, Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, Luleå 97187, Sweden
- Blanca Jalvo - Department of Materials and Environmental Chemistry, Stockholm University, Stockholm 10691, Sweden
- Philipp Moritz - Clausthal Centre of Material Technology, Clausthal University of Technology, Clausthal-Zellerfeld 38678, Germany; http://orcid.org/0000-0002-7582-101X
- Leonidas Matsakas - Biochemical Process Engineering, Chemical Engineering, Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, Luleå 97187, Sweden; http://orcid.org/0000-0002-3687-6173
- Ulrika Rova - Biochemical Process Engineering, Chemical Engineering, Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, Luleå 97187, Sweden
- Oliver Höfft - Institute of Electrochemistry, Clausthal University of Technology, Clausthal-Zellerfeld 38678, Germany; http://orcid.org/0000-0002-1313-3166
- Georgia Sourkouni - Clausthal Centre of Material Technology, Clausthal University of Technology, Clausthal-Zellerfeld 38678, Germany
- Wolfgang Maus-Friedrichs - Clausthal Centre of Material Technology, Clausthal University of Technology, Clausthal-Zellerfeld 38678, Germany
Author Contributions
A.K. and B.J. equally contributed to this work.
Notes
The authors declare no competing financial interest.

Acknowledgments

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Part of this work was conducted within the frame of IKY-DAAD (2018-2019) ″Enzymatic superficial modification of natural and synthetic polymers and their spectroscopic analysis″ project, funded by a bilateral agreement between German Academic Exchange Service and Greek State Scholarship Foundation. Fredrik Norén from Marine Feed Sweden AB is greatly acknowledged for providing the tunic material.

Abbreviations

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TNC	tunicate nanocrystal
LPMO	lytic polysaccharide monooxygenase
OS	organosolv
DLS	dynamic light scattering
AFM	atomic force microscopy
XPS	X-ray photoelectron spectroscopy
XRD	X-ray diffraction
SEM	scanning electron microscopy
TGA	thermogravimetric analysis

References

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Salas, C.; Nypelö, T.; Rodriguez-Abreu, C.; Carrillo, C.; Rojas, O. J. Nanocellulose properties and applications in colloids and interfaces. 2014. Curr. Opin. Colloid Interface Sci. 2014, 19, 383– 396, DOI: 10.1016/j.cocis.2014.10.003
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Nanocellulose properties and applications in colloids and interfaces
Salas, Carlos; Nypelo, Tiina; Rodriguez-Abreu, Carlos; Carrillo, Carlos; Rojas, Orlando J.
Current Opinion in Colloid & Interface Science (2014), 19 (5), 383-396CODEN: COCSFL; ISSN:1359-0294. (Elsevier Ltd.)
In this review we introduce recent advances in the development of cellulose nanomaterials and the construction of high order structures by applying some principles of colloid and interface science. These efforts take advantage of natural assemblies in the form of fibers that nature constructs by a biogenetic bottom-up process that results in hierarchical systems encompassing a wide range of characteristic sizes. Following the reverse process, a top-down deconstruction, cellulose materials can be cleaved from fiber cell walls. The resulting nanocelluloses, mainly cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC, i.e., defect-free, rod-like cryst. residues after acid hydrolysis of fibers), have been the subject of recent interest. This originates from the appealing intrinsic properties of nanocelluloses: nanoscale dimensions, high surface area, morphol., low d., chirality and thermo-mech. performance. Directing their assembly into multiphase structures is a quest that can yield useful outcomes in many revolutionary applications. As such, we discuss the use of non-specific forces to create thin films of nanocellulose at the air-solid interface for applications in nano-coatings, sensors, etc. Assemblies at the liq.-liq. and air-liq. interfaces will be highlighted as means to produce Pickering emulsions, foams and aerogels. Finally, the prospects of a wide range of hybrid materials and other systems that can be manufd. via self and directed assembly will be introduced in light of the unique properties of nanocelluloses.
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Lee, K.-Y.; Aitomäki, Y.; Berglund, L. A.; Oksman, K.; Bismarck, A. On the use of nanocellulose as reinforcement in polymer matrix composites. Compos. Sci. Technol. 2014, 105, 15– 27, DOI: 10.1016/j.compscitech.2014.08.032
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On the use of nanocellulose as reinforcement in polymer matrix composites
Lee, Koon-Yang; Aitomaki, Yvonne; Berglund, Lars A.; Oksman, Kristiina; Bismarck, Alexander
Composites Science and Technology (2014), 105 (), 15-27CODEN: CSTCEH; ISSN:0266-3538. (Elsevier Ltd.)
A review. Nanocellulose is often being regarded as the next generation renewable reinforcement for the prodn. of high performance biocomposites. This feature article reviews the various nanocellulose reinforced polymer composites reported in literature and discusses the potential of nanocellulose as reinforcement for the prodn. of renewable high performance polymer nanocomposites. The theor. and exptl. detd. tensile properties of nanocellulose are also reviewed. In addn. to this, the reinforcing ability of BC and NFC is juxtaposed. In order to analyze the various cellulose-reinforced polymer nanocomposites reported in literature, Cox-Krenchel and rule-of-mixt. models have been used to elucidate the potential of nanocellulose in composite applications. There may be potential for improvement since the tensile modulus and strength of most cellulose nanocomposites reported in literature scale linearly with the tensile modulus and strength of the cellulose nanopaper structures. Better dispersion of individual cellulose nanofibers in the polymer matrix may improve composite properties.
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Klemm, D.; Kramer, F.; Moritz, S.; Lindstrom, T.; Ankerfors, M.; Gray, D.; Dorris, A. Nanocelluloses: a new family of nature-based materials. Angew. Chem., Int. Ed. 2011, 50, 5438– 5466, DOI: 10.1002/anie.201001273
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Nanocelluloses: A New Family of Nature-Based Materials
Klemm, Dieter; Kramer, Friederike; Moritz, Sebastian; Lindstroem, Tom; Ankerfors, Mikael; Gray, Derek; Dorris, Annie
Angewandte Chemie, International Edition (2011), 50 (24), 5438-5466CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)
A review. Cellulose fibrils with widths in the nanometer range are nature-based materials with unique and potentially useful features. Most importantly, these novel nanocelluloses open up the strongly expanding fields of sustainable materials and nanocomposites, as well as medical and life-science devices, to the natural polymer cellulose. The nanodimensions of the structural elements result in a high surface area and hence the powerful interaction of these celluloses with surrounding species. This Review assembles the current knowledge on the isolation of microfibrillated cellulose from wood and its application in nanocomposites; the prepn. of nanocryst. cellulose and its use as a reinforcing agent; and the biofabrication of bacterial nanocellulose, as well as its evaluation as a biomaterial for medical implants.
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Habibi, Y.; Lucia, L. A.; Rojas, O. J. Cellulose nanocrystals: chemistry, self-assembly, and applications. Chem. Rev. 2010, 110, 3479– 3500, DOI: 10.1021/cr900339w
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Cellulose Nanocrystals: Chemistry, Self-Assembly, and Applications
Habibi, Youssef; Lucia, Lucian A.; Rojas, Orlando J.
Chemical Reviews (Washington, DC, United States) (2010), 110 (6), 3479-3500CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)
A review discussing chem. and phys. features of the most dominant fundamental building block in the biosphere, cellulose nanocrystals. A brief introduction to cellulose was followed by the discussion of morphol., chem., including prepn. and chem. routes for functionalization, and self-assembly in various media under various conditions, and applications in the nanocomposites.
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Mariano, M.; El Kissi, N.; Dufresne, A. Cellulose nanocrystals and related nanocomposites: review of some properties and challenges. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 791– 806, DOI: 10.1002/polb.23490
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Cellulose nanocrystals and related nanocomposites: Review of some properties and challenges
Mariano, Marcos; El Kissi, Nadia; Dufresne, Alain
Journal of Polymer Science, Part B: Polymer Physics (2014), 52 (12), 791-806CODEN: JPBPEM; ISSN:0887-6266. (John Wiley & Sons, Inc.)
A review. Cellulosic nanoparticles with high Young's modulus, crystallinity, sp. surface area, and aspect ratio can be found in the natural structure of plant fibers. Indeed, lignocellulosic fibers consist of semicryst. cellulose nanofibrils embedded in an amorphous matrix mainly composed of lignin and hemicelluloses. These nanostructures give the mech. strength to higher plant cells, and are biodegradable, renewable, resistant, and widely available to produce nanocomposites with low d., and improved and controlled mech., optical, and barrier properties. Nanoparticles can be extd. from cellulose using a top-down mech. or chem. assisted deconstructing strategy, and owing to their highly reactive surface ensuing nanomaterials can be chem. modified to tailor their properties for a wide range of applications. This review is limited to cellulose chem. extd. nanocrystals and aims to provide an overview about several aspects that involve this material, including sources, properties, challenges, and perspectives. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014.
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Jonoobi, M.; Oladi, R.; Davoudpour, Y.; Oksman, K.; Dufrense, A.; Hamzeh, Y.; Davoodi, R. Different preparation methods and properties of nanostructured cellulose from various natural resources and residues: a review. Cellulose 2015, 22, 935– 969, DOI: 10.1007/s10570-015-0551-0
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Different preparation methods and properties of nanostructured cellulose from various natural resources and residues: a review
Jonoobi, Mehdi; Oladi, Reza; Davoudpour, Yalda; Oksman, Kristiina; Dufresne, Alain; Hamzeh, Yahya; Davoodi, Reza
Cellulose (Dordrecht, Netherlands) (2015), 22 (2), 935-969CODEN: CELLE8; ISSN:0969-0239. (Springer)
A review. The main goal of this article is to provide an overview of recent research in the area of cellulose nanomaterial prodn. from different sources. Due to their abundance, renewability, high strength and stiffness, eco-friendliness and low wt., numerous studies have been reported on the isolation of cellulose nanomaterials from different cellulosic sources and their use in high-performance applications. This report covers an introduction to the definition of nanocellulose as well as the methods used for isolation of nanomaterials (including nanocrystals and nanofibers, CNCs and CNFs, resp.) from various sources. The web-like network structure (CNFs) can be extd. from natural sources using mech. processes, which include high-pressure homogenization, grinding and refining treatments. Also, rod-like CNCs can be isolated from sources such as wood, plant fibers, agricultural and industrial bioresidues, tunicates and bacterial cellulose using an acid hydrolysis process. Following this, the article focuses on the characterization methods, material properties and structures. Encyclopedic characteristics of CNFs and CNCs obtained from different source materials and/or studies are also included. The current report is a comprehensive review of the literature regarding nanocellulose isolation and demonstrates the potential of cellulose nanomaterials for a wide range of high-tech applications.
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Börjesson, M.; Westman, G. Crystalline Nanocellulose — Preparation, Modification, and Properties, Cellulose-Fundamental Aspects and Current Trends, Matheus Poletto and Heitor Luiz Ornaghi Junior, IntechOpen, December 9th 2015. DOI: 10.5772/61899 . Available from: https://www.intechopen.com/books/cellulose-fundamental-aspects-and-current-trends/crystalline-nanocellulose-preparation-modification-and-properties
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Zhao, Y.; Li, J. Excellent chemical and material cellulose from tunicates: diversity in cellulose production yield and chemical and morphological structures from different tunicate species. Cellulose 2014, 21, 3427– 3441, DOI: 10.1007/s10570-014-0348-6
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Excellent chemical and material cellulose from tunicates: diversity in cellulose production yield and chemical and morphological structures from different tunicate species
Zhao, Yadong; Li, Jiebing
Cellulose (Dordrecht, Netherlands) (2014), 21 (5), 3427-3441CODEN: CELLE8; ISSN:0969-0239. (Springer)
The high crystallinity and the high microfibrils aspect ratio of tunicate cellulose (TC) indicate TC's excellent chem. and material applications. However, its quantity and quality from different species have never been systematically reported and compared. In this study, the tunics of Ciona intestinalis (CI), Ascidia sp. (AS), Halocynthia roretzi (HR) and Styela plicata (SP) were processed to TC after an identical prehydrolysis-kraft cooking-bleaching sequence, while the tunicate fibrils were chem. and structurally characterized in situ and during the sequence. All tunics studied were composed of cryst. cellulose embedded with protein, lipids, sulfated glycans and mucopolysaccharides. The native composite structures are all very compact. However, the tunics from Phlebobranchia order (CI and AS) are soft, while those from Stolidobranchia, HR and SP, are hard. Fibrous cellulose could be prepd. after removing the lipids, sulfated glycans and mucopolysaccharides through prehydrolysis, protein removal through kraft cooking and a final purifn. by bleaching. The final product is ∼100% pure cellulose which is in large mol. masses, composed of highly cryst. Iβ crystals, in elementary microfibrils form, with high sp. surface area and thermal stability. There were lower TC yields from the soft tunics than from the hard ones. The cellulose fibrils had a section shape of lozenges with higher crystallinity. This study demonstrates that TC could be obtained in different yields and exhibited different chem. and morphol. structures depending on the species. There is a great potential of tunicate resources for prepg. excellent chem. and material cellulose.
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Mathew, A. P.; Dufresne, A. Morphological investigation of nanocomposites from sorbitol plasticized starch and tunicin whiskers. Biomacromolecules 2002, 3, 609– 617, DOI: 10.1021/bm0101769
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Morphological investigation of nanocomposites from sorbitol plasticized starch and tunicin whiskers
Mathew, Aji P.; Dufresne, Alain
Biomacromolecules (2002), 3 (3), 609-617CODEN: BOMAF6; ISSN:1525-7797. (American Chemical Society)
Nanocomposites were prepd. from waxy maize starch (I) plasticized with sorbitol as the matrix and a stable aq. suspension of tunicin (II) whiskers -- an animal cellulose -- as the reinforcing phase. The composites were conditioned at different relative humidity levels. The conditioned films were characterized using SEM, DSC, water uptake expts., and WAXS studies. Contrarily to a previous report concerning II whisker-filled glycerol plasticized I nanocomposites (Macromols. 2000, 33, 8344), the present system exhibited a single glass-rubber transition, and no evidence of transcrystn. of amylopectin (III) on II whisker surfaces and resultant anti-plasticizing effects were obsd. It was shown that the glass-rubber transition temp. of the plasticized III matrix 1st increases up to a whiskers content around 10-15 wt.%, and then decreases. A significant increase in crystallinity was obsd. in the composites by increasing either moisture content or whiskers content.
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Zhao, Y.; Moser, C.; Lindström, M. E.; Henriksson, G.; Li, J. Cellulose nanofibers from softwood, hardwood, and tunicate: preparation–structure–film performance interrelation. Appl. Mater. Interfaces 2017, 9, 13508– 13519, DOI: 10.1021/acsami.7b01738
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Cellulose Nanofibers from Softwood, Hardwood, and Tunicate: Preparation-Structure-Film Performance Interrelation
Zhao, Yadong; Moser, Carl; Lindstroem, Mikael E.; Henriksson, Gunnar; Li, Jiebing
ACS Applied Materials & Interfaces (2017), 9 (15), 13508-13519CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
This work reveals the structural variations of cellulose nanofibers (CNF) prepd. from different cellulose sources, softwood (Picea abies), hardwood (E. grandis x E. urophylla) and tunicate (Ciona intestinalis), using different prepn. processes, and their correlations to the formation and performance of the films prepd. from the CNF. Here the CNF are prepd. from wood chem. pulps and tunicate isolated cellulose by an identical homogenization treatment subsequent to either an enzymic hydrolysis or a 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-mediated oxidn. They show a large structural diversity in terms of chem., morphol., and cryst. structure. Among others, the tunicate CNF consist of purer cellulose and have higher d.p. than wood CNF. Introduction of surface charges via the TEMPO-mediated oxidn. is found to have significant impacts on the structure, morphol., optical, mech., thermal, and hydrophobic properties of the prepd. films. For example, the film d. is closely related to the charge d. of the used CNF and the tensile stress of the films is correlated to the crystallinity index of the CNF. In turn the CNF structure is detd. by the cellulose sources and the prepn. processes. This study provides useful information and knowledge for understanding the importance of the raw material for the quality of CNF for various types of application.
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Sacui, I. A.; Nieuwendaal, R. C.; Burnett, D. J.; Stranick, S. J.; Jorfi, M.; Weder, C.; Foster, E. J.; Olsson, R. T.; Gilman, J. W. Comparison of the properties of cellulose nanocrystals and cellulose nanofibrils isolated from bacteria, tunicate, and wood processed using acid, enzymatic, mechanical, and oxidative methods. ACS Appl. Mater. Interfaces 2014, 6, 6127– 6138, DOI: 10.1021/am500359f
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Comparison of the Properties of Cellulose Nanocrystals and Cellulose Nanofibrils Isolated from Bacteria, Tunicate, and Wood Processed Using Acid, Enzymatic, Mechanical, and Oxidative Methods
Sacui, Iulia A.; Nieuwendaal, Ryan C.; Burnett, Daniel J.; Stranick, Stephan J.; Jorfi, Mehdi; Weder, Christoph; Foster, E. Johan; Olsson, Richard T.; Gilman, Jeffery W.
ACS Applied Materials & Interfaces (2014), 6 (9), 6127-6138CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
This work describes the measurement and comparison of several important properties of native cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs), such as crystallinity, morphol., aspect ratio, and surface chem. Measurement of the fundamental properties of seven different CNCs/CNFs, from raw material sources (bacterial, tunicate, and wood) using typical hydrolysis conditions (acid, enzymic, mech., and 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-mediated oxidn.), was accomplished using a variety of measurement methods. Atomic force microscopy (AFM), TEM, and 13C cross-polarization magic angle spinning (CPMAS) NMR spectroscopy were used to conclude that CNCs, which are rodlike in appearance, have a higher crystallinity than CNFs, which are fibrillar in appearance. CNC aspect ratio distributions were measured and ranged from 148±147 for tunicate-CNCs to 23±12 for wood-CNCs. Hydrophobic interactions, measured using inverse gas chromatog. (IGC), were found to be an important contribution to the total surface energy of both types of cellulose. In all cases, a trace amt. of naturally occurring fluorescent compds. was obsd. after hydrolysis. Confocal and Raman microscopy were used to confirm that the fluorescent species were unique for each cellulose source, and demonstrated that such methods can be useful for monitoring purity during CNC/CNF processing. This study reveals the broad, tunable, multi-dimensional material space in which CNCs and CNFs exist.
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Elazzouzi-Hafraoui, S.; Nishiyama, Y.; Putaux, J.-L.; Heux, L.; Dubreuil, F.; Rochas, C. The shape and size distribution of crystalline nanoparticles prepared by acid hydrolysis of native cellulose. Biomacromolecules 2008, 9, 57– 65, DOI: 10.1021/bm700769p
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The Shape and Size Distribution of Crystalline Nanoparticles Prepared by Acid Hydrolysis of Native Cellulose
Elazzouzi-Hafraoui, Samira; Nishiyama, Yoshiharu; Putaux, Jean-Luc; Heux, Laurent; Dubreuil, Frederic; Rochas, Cyrille
Biomacromolecules (2008), 9 (1), 57-65CODEN: BOMAF6; ISSN:1525-7797. (American Chemical Society)
The shape and size distribution of cryst. nanoparticles resulting from the sulfuric acid hydrolysis of cellulose from cotton, Avicel, and tunicate were investigated using transmission electron microscopy (TEM) and at. force microscopy (AFM) as well as small- and wide-angle X-ray scattering (SAXS and WAXS). Images of neg. stained and cryo-TEM specimens showed that the majority of cellulose particles were flat objects constituted by elementary crystallites whose lateral adhesion was resistant against hydrolysis and sonication treatments. Moreover, tunicin whiskers were described as twisted ribbons with an estd. pitch of 2.4-3.2 μm. Length and width distributions of all samples were generally well described by log-normal functions, with the exception of tunicin, which had less lateral aggregation. AFM observation confirmed that the thickness of the nanocrystals was almost const. for a given origin and corresponded to the crystallite size measured from peak broadening in WAXS spectra. Exptl. SAXS profiles were numerically simulated, combining the dimensions and size distribution functions detd. by the various techniques.
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Mathew, A. P.; Thielemans, W.; Dufresne, A. Mechanical properties of nanocomposites from sorbitol plasticized starch and tunicin whiskers. J. Appl. Polym. Sci. 2008, 109, 4065– 4074, DOI: 10.1002/app.28623
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Mechanical properties of nanocomposites from sorbitol plasticized starch and tunicin whiskers
Mathew, Aji P.; Thielemans, W.; Dufresne, Alain
Journal of Applied Polymer Science (2008), 109 (6), 4065-4074CODEN: JAPNAB; ISSN:0021-8995. (John Wiley & Sons, Inc.)
Nanocomposite materials were obtained using sorbitol plasticized waxy maize starch as matrix and tunicin whiskers as the reinforcement. The effect of filler load (0-25 wt. % whiskers) and the relative humidity levels (0-98%) on the mech. behavior of the films are discussed for linear and nonlinear deformation. The performance of the films is explained, based on the morphol. and structural behavior of the composite materials (Mathew and Dufresne, Biomacromols. 2002, 3, 609). The nanocomposites exhibit good mech. strength due to the strong interaction between tunicin whiskers, matrix, plasticizer (sorbitol), and water, and due to the ability of the cellulose filler to form a rigid three-dimensional network. The evolution of Tg as a function of relative humidity level and filler load is studied in detail. A decrease in crystallinity of the amylopectin phase is obsd. at high filler loads, due to the resistance to chain rearrangement imposed by the whiskers. The mech. strength increased proportionally with filler loads, showing an effective stress transfer from the matrix to the whiskers. An even distribution of whiskers (as detd. by SEM) and plasticizer in the matrix contributes to the mech. performance. The mech. properties of the nanocomposites showed a strong dependence on relative humidity conditions.
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Squinca, P.; Bilatto, S.; Badino, A. C.; Farinas, C. S. Nanocellulose production in future biorefineries: an integrated approach using tailor-made enzymes. ACS Sustainable Chem. Eng. 2020, 8, 2277– 2286, DOI: 10.1021/acssuschemeng.9b06790
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Nanocellulose Production in Future Biorefineries: An Integrated Approach Using Tailor-Made Enzymes
Squinca, Paula; Bilatto, Stanley; Badino, Alberto C.; Farinas, Cristiane S.
ACS Sustainable Chemistry & Engineering (2020), 8 (5), 2277-2286CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)
The development of process engineering approaches to integrate the prodn. of biofuels and high value-added biobased products, such as enzymes and nanocellulose, is crucial to improve the financial performance and sustainability of lignocellulosic biomass biorefineries. Here, the feasibility of applying enzymes produced on-site to obtain nanocellulose was evaluated using eucalyptus cellulose pulp as a model feedstock. A systematic anal. of the structural properties of the nanomaterials obtained after hydrolysis using a cellulolytic enzymic complex with high endoglucanase specific activity (17.09 IU/mgprotein), produced by Aspergillus niger, followed by sonication, revealed that longer ball milling pretreatment and reaction times favored extn. of the cellulose nanocrystals (CNCs). The highest yield (24.6%) of CNCs was achieved using 96 h of enzymic hydrolysis of the ball-milled cellulose pulp, followed by sonication for 5 min. The CNCs presented approx. lengths of 294.0 nm and diams. of 24.0 nm, and the crystallinity index increased from 57.5% to 78.3%, compared to the cellulose pulp that was only ball milled. These findings demonstrated that nanocelluloses could be successfully extd. using on-site produced enzymes and that the sustainable integrated process reported here could contribute to the development of the nascent biobased economy. Cellulose nanocrystals were obtained by enzymic hydrolysis using on-site produced enzymes and eucalyptus cellulose pulp in a sustainable integrated process.
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Henriksson, M.; Henriksson, G.; Berglund, L. A.; Lindström, T. An environmentally friendly method for enzyme-assisted preparation of microfibrillated cellulose (MFC) nanofibers. Eur. Polym. J. 2007, 43, 3434– 3441, DOI: 10.1016/j.eurpolymj.2007.05.038
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An environmentally friendly method for enzyme-assisted preparation of microfibrillated cellulose (MFC) nanofibers
Henriksson, M.; Henriksson, G.; Berglund, L. A.; Lindstroem, T.
European Polymer Journal (2007), 43 (8), 3434-3441CODEN: EUPJAG; ISSN:0014-3057. (Elsevier Ltd.)
Microfibrillated cellulose nanofibers (MFC) provide strong reinforcement in polymer nanocomposites. In the present study, cellulosic wood fiber pulps are treated by endoglucanases or acid hydrolysis in combination with mech. shearing in order to disintegrate MFC from the wood fiber cell wall. After successful disintegration, the MFC nanofibers were studied by at. force microscopy (AFM). Enzyme-treatment was found to facilitate disintegration, and the MFC nanofibers produced also showed higher av. molar mass and larger aspect ratio than nanofibers resulting from acidic pretreatment.
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Hu, J.; Tian, D.; Renneckar, S.; Saddler, J. N. Enzyme-mediated nanofibrillation of cellulose by the synergistic actions of an endoglucanase, lytic polysaccharide monooxygenase (LPMO) and xylanase. Sci. Rep. 2018, 8, 3195, DOI: 10.1038/s41598-018-21016-6
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Enzyme mediated nanofibrillation of cellulose by the synergistic actions of an endoglucanase, lytic polysaccharide monooxygenase (LPMO) and xylanase
Hu Jinguang; Tian Dong; Saddler Jack N; Tian Dong; Renneckar Scott
Scientific reports (2018), 8 (1), 3195 ISSN:.
Physiochemical methods have generally been used to "open-up" biomass substrates/pulps and have been the main method used to fibrillate cellulose. However, recent work has shown that canonical cellulase enzymes such as endoglucanases, in combination with "amorphogenesis inducing" proteins such as lytic polysaccharide monooxygenases (LPMO), swollenin and hemicellulases, are able to increase cellulose accessibility. In the work reported here different combinations of endoglucanase, LPMO and xylanase were applied to Kraft pulps to assess their potential to induce fibrillation at low enzyme loading over a short time period. Although gross fiber properties (fiber length, width and morphology) were relatively unchanged, over a short period of time, the intrinsic physicochemical characteristics of the pulp fibers (e.g. cellulose accessibility/DP/crystallinity/charge) were positively enhanced by the synergistic cooperation of the enzymes. LPMO addition resulted in the oxidative cleavage of the pulps, increasing the negative charge (~100 mmol kg(-1)) on the cellulose fibers. This improved cellulose nanofibrilliation while stabilizing the nanofibril suspension (zeta potential ζ = ~60 mV), without sacrificing nanocellulose thermostability. The combination of endoglucanase, LPMO and xylanases was shown to facilitate nanofibrillation, potentially reducing the need for mechanical refining while resulting in a pulp with a more uniform nanofibril composition.
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Hu, J.; Arantes, V.; Pribowo, A.; Saddler, J. N. The synergistic action of accessory enzymes enhances the hydrolytic potential of a “cellulase mixture” but is highly substrate specific. Biotechnol. Biofuels 2013, 6, 112, DOI: 10.1186/1754-6834-6-112
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The synergistic action of accessory enzymes enhances the hydrolytic potential of a "cellulase mixture" but is highly substrate specific
Hu, Jinguang; Arantes, Valdeir; Pribowo, Amadeus; Saddler, Jack N.
Biotechnology for Biofuels (2013), 6 (), 112CODEN: BBIIFL; ISSN:1754-6834. (BioMed Central Ltd.)
Currently, the amt. of protein/enzyme required to achieve effective cellulose hydrolysis is still too high. One way to reduce the amt. of protein/enzyme required is to formulate a more efficient enzyme cocktail by adding so-called accessory enzymes such as xylanase, lytic polysaccharide monooxygenase (AA9, formerly known as GH61), etc., to the cellulase mixt. Previous work has shown the strong synergism that can occur between cellulase and xylanase mixts. during the hydrolysis of steam pretreated corn stover, requiring lower protein loading to achieve effective hydrolysis. However, relatively high loadings of xylanases were required. When family 10 and 11 endo-xylanases and family 5 xyloglucanase were supplemented to a com. cellulase mixt. varying degrees of improved hydrolysis over a range of pretreated, lignocellulosic substrates were obsd. Results: The potential synergistic interactions between cellulase monocomponents and hemicellulases from family 10 and 11 endo-xylanases (GH10 EX and GH11 EX) and family 5 xyloglucanase (GH5 XG), during hydrolysis of various steam pretreated lignocellulosic substrates, were assessed. It was apparent that the hydrolytic activity of cellulase monocomponents was enhanced by the addn. of accessory enzymes although the "boosting" effect was highly substrate specific. The GH10 EX and GH5 XG both exhibited broad substrate specificity and showed strong synergistic interaction with the cellulases when added individually. The GH10 EX was more effective on steam pretreated agriculture residues and hardwood substrates whereas GH5 XG addn. was more effective on softwood substrates. The synergistic interaction between GH10 EX and GH5 XG when added together further enhanced the hydrolytic activity of the cellulase enzymes over a range of pretreated lignocellulosic substrates. GH10 EX addn. could also stimulate further cellulose hydrolysis when added to the hydrolysis reactions when the rate of hydrolysis had levelled off. Conclusions: Endo-xylanases and xyloglucanases interacted synergistically with cellulases to improve the hydrolysis of a range of pretreated lignocellulosic substrates. However, the extent of improved hydrolysis was highly substrate dependent. It appears that those accessory enzymes, such as GH10 EX and GH5 XG, with broader substrate specificities promoted the greatest improvements in the hydrolytic performance of the cellulase mixt. on all of the pretreated biomass substrates.
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Westereng, B.; Ishida, T.; Vaaje-Kolstad, G.; Wu, M.; Eijsink, V. G.; Igarashi, K.; Samejima, M.; Ståhlberg, J.; Horn, S. J.; Sandgren, M. The putative endoglucanase PcGH61D from Phanerochaete chrysosporium is a metal-dependent oxidative enzyme that cleaves cellulose. PLoS One 2011, 6, e27807 DOI: 10.1371/journal.pone.0027807
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The putative endoglucanase PcGH61D from Phanerochaete chrysosporium is a metal-dependent oxidative enzyme that cleaves cellulose
Westereng, Bjoerge; Ishida, Takuya; Vaaje-Kolstad, Gustav; Wu, Miao; Eijsink, Vincent G. H.; Igarashi, Kiyohiko; Samejima, Masahiro; Staahlberg, Jerry; Horn, Svein J.; Sandgren, Mats
PLoS One (2011), 6 (11), e27807CODEN: POLNCL; ISSN:1932-6203. (Public Library of Science)
Many fungi growing on plant biomass produce proteins currently classified as glycoside hydrolase family 61 (GH61), some of which are known to act synergistically with cellulases. In this study we show that PcGH61D, the gene product of an open reading frame in the genome of Phanerochaete chrysosporium, is an enzyme that cleaves cellulose using a metal-dependent oxidative mechanism that leads to generation of aldonic acids. The activity of this enzyme and its beneficial effect on the efficiency of classical cellulases are stimulated by the presence of electron donors. Expts. with reduced cellulose confirmed the oxidative nature of the reaction catalyzed by PcGH61D and indicated that the enzyme may be capable of penetrating into the substrate. Considering the abundance of GH61-encoding genes in fungi and genes encoding their functional bacterial homologues currently classified as carbohydrate binding modules family 33 (CBM33), this enzyme activity is likely to turn out as a major determinant of microbial biomass-degrading efficiency.
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Harris, P. V.; Welner, D.; McFarland, K. C.; Re, E.; Navarro Poulsen, J. C.; Brown, K.; Salbo, R.; Ding, H.; Vlasenko, E.; Merino, S.; Xu, F.; Cherry, J.; Larsen, S.; Lo Leggio, L. Stimulation of lignocellulosic biomass hydrolysis by proteins of Glycoside Hydrolase Family 61: Structure and function of a large, enigmatic family. Biochemistry 2010, 49, 3305– 3316, DOI: 10.1021/bi100009p
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Stimulation of Lignocellulosic Biomass Hydrolysis by Proteins of Glycoside Hydrolase Family 61: Structure and Function of a Large, Enigmatic Family
Harris, Paul V.; Welner, Ditte; McFarland, K. C.; Re, Edward; Navarro Poulsen, Jens-Christian; Brown, Kimberly; Salbo, Rune; Ding, Hanshu; Vlasenko, Elena; Merino, Sandy; Xu, Feng; Cherry, Joel; Larsen, Sine; Lo Leggio, Leila
Biochemistry (2010), 49 (15), 3305-3316CODEN: BICHAW; ISSN:0006-2960. (American Chemical Society)
Currently, the relatively high cost of enzymes such as glycoside hydrolases that catalyze cellulose hydrolysis represents a barrier to commercialization of a biorefinery capable of producing renewable transportable fuels such as ethanol from abundant lignocellulosic biomass. Among the many families of glycoside hydrolases that catalyze cellulose and hemicellulose hydrolysis, few are more enigmatic than family 61 (GH61), originally classified based on measurement of very weak endo-1,4-β-D-glucanase activity in one family member. Here we show that certain GH61 proteins lack measurable hydrolytic activity by themselves but in the presence of various divalent metal ions can significantly reduce the total protein loading required to hydrolyze lignocellulosic biomass. We also solved the structure of one highly active GH61 protein and find that it is devoid of conserved, closely juxtaposed acidic side chains that could serve as general proton donor and nucleophile/base in a canonical hydrolytic reaction, and we conclude that the GH61 proteins are unlikely to be glycoside hydrolases. Structure-based mutagenesis shows the importance of several conserved residues for GH61 function. By incorporating the gene for one GH61 protein into a com. Trichoderma reesei strain producing high levels of cellulolytic enzymes, we are able to reduce by 2-fold the total protein loading (and hence the cost) required to hydrolyze lignocellulosic biomass.
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Vaaje-Kolstad, G.; Westereng, B.; Horn, S. J.; Liu, Z.; Zhai, H.; So̷rlie, M.; Eijsink, V. G. An oxidative enzyme boosting the enzymatic conversion of recalcitrant polysaccharides. Science 2010, 330, 219– 222, DOI: 10.1126/science.1192231
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An Oxidative Enzyme Boosting the Enzymatic Conversion of Recalcitrant Polysaccharides
Vaaje-Kolstad, Gustav; Westereng, Bjorge; Horn, Svein J.; Liu, Zhanliang; Zhai, Hong; Sorlie, Morten; Eijsink, Vincent G. H.
Science (Washington, DC, United States) (2010), 330 (6001), 219-222CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
Efficient enzymic conversion of cryst. polysaccharides is crucial for an economically and environmentally sustainable bioeconomy but remains unfavorably inefficient. We describe an enzyme that acts on the surface of cryst. chitin, where it introduces chain breaks and generates oxidized chain ends, thus promoting further degrdn. by chitinases. This enzymic activity was discovered and further characterized by using mass spectrometry and chromatog. sepn. methods to detect oxidized products generated in the absence or presence of H218O or 18O2. There are strong indications that similar enzymes exist that work on cellulose. Our findings not only demonstrate the existence of a hitherto unknown enzyme activity but also provide new avenues toward more efficient enzymic conversion of biomass.
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Forsberg, Z.; Vaaje-Kolstad, G.; Westereng, B.; Bunæs, A. C.; Stenstro̷m, Y.; MacKenzie, A.; So̷rlie, M.; Horn, S. J.; Eijsink, V. G. Cleavage of cellulose by a CBM33 protein. Protein Sci. 2011, 20, 1479– 1483, DOI: 10.1002/pro.689
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Cleavage of cellulose by a CBM33 protein
Forsberg, Zarah; Vaaje-Kolstad, Gustav; Westereng, Bjorge; Bunaes, Anne C.; Stenstrom, Yngve; MacKenzie, Alasdair; Sorlie, Morten; Horn, Svein J.; Eijsink, Vincent G. H.
Protein Science (2011), 20 (9), 1479-1483CODEN: PRCIEI; ISSN:1469-896X. (Wiley-Blackwell)
Bacterial proteins categorized as family 33 carbohydrate-binding modules (CBM33) were recently shown to cleave cryst. chitin, using a mechanism that involves hydrolysis and oxidn. Here, the authors show that some members of the CBM33 family cleave cryst. cellulose as demonstrated by chromatog. and mass spectrometric analyses of sol. products released from Avicel or filter paper on incubation with CelS2, a CBM33-contg. protein from Streptomyces coelicolor A3(2). These enzymes acted synergistically with cellulases and may thus become important tools for efficient conversion of lignocellulosic biomass. Fungal proteins classified as glycoside hydrolase family 61 that are known to act synergistically with cellulases are likely to use a similar mechanism.
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Quinlan, R. J.; Sweeney, M. D.; Lo Leggio, L.; Otten, H.; Poulsen, J. C.; Johansen, K. S.; Krogh, K. B.; Jo̷rgensen, C. I.; Tovborg, M.; Anthonsen, A.; Tryfona, T.; Walter, C. P.; Dupree, P.; Xu, F.; Davies, G. J.; Walton, P. H. Insights into the oxidative degradation of cellulose by a copper metalloenzyme that exploits biomass components. Proc. Natl. Acad. Sci. U. S. A. 2011, 108, 15079– 15084, DOI: 10.1073/pnas.1105776108
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Insights into the oxidative degradation of cellulose by a copper metalloenzyme that exploits biomass components
Quinlan, R. Jason; Sweeney, Matt D.; Lo Leggio, Leila; Otten, Harm; Poulsen, Jens-Christian N.; Johansen, Katja Salomon; Krogh, Kristian B. R. M.; Jorgensen, Christian Isak; Tovborg, Morten; Anthonsen, Annika; Tryfona, Theodora; Walter, Clive P.; Dupree, Paul; Xu, Feng; Davies, Gideon J.; Walton, Paul H.
Proceedings of the National Academy of Sciences of the United States of America (2011), 108 (37), 15079-15084, S15079/1-S15079/10CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
The enzymic degrdn. of recalcitrant plant biomass is one of the key industrial challenges of the 21st century. Accordingly, there is a continuing drive to discover new routes to promote polysaccharide degrdn. Perhaps the most promising approach involves the application of 'cellulase-enhancing factors', such as those from the glycoside hydrolase (CAZy) GH61 family. Here we show that GH61 enzymes are a unique family of copper-dependent oxidases. We demonstrate that copper is needed for GH61 maximal activity and that the formation of cellodextrin and oxidized cellodextrin products by GH61 is enhanced in the presence of small mol. redox-active cofactors such as ascorbate and gallate. By using ESR spectroscopy and single-crystal X-ray diffraction, the active site of GH61 is revealed to contain a type II copper and, uniquely, a methylated histidine in the copper's coordination sphere, thus providing an innovative paradigm in bioinorg. enzymic catalysis.
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Beeson, W. T.; Phillips, C. M.; Cate, J. H. D.; Marletta, M. A. Oxidative cleavage of cellulose by fungal copper-dependent polysaccharide monooxygenases. J. Am. Chem. Soc. 2011, 134, 890– 892, DOI: 10.1021/ja210657t
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Moreau, C.; Tapin-Lingua, S.; Grisel, S.; Gimbert, I.; Le Gall, S.; Petit-Conil, M.; Berrin, J. G.; Cathala, B.; Villares, A. Lytic polysaccharide monooxygenases (LPMOs) facilitate cellulose nanofibrils production. Biotechnol. Biofuels. 2019, 12, 156, DOI: 10.1186/s13068-019-1501-0
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Lytic polysaccharide monooxygenases (LPMOs) facilitate cellulose nanofibrils production
Moreau Celine; Le Gall Sophie; Cathala Bernard; Villares Ana; Tapin-Lingua Sandra; Grisel Sacha; Gimbert Isabelle; Berrin Jean-Guy; Meyer Valerie; Petit-Conil Michel
Biotechnology for biofuels (2019), 12 (), 156 ISSN:1754-6834.
BACKGROUND: Lytic polysaccharide monooxygenases (LPMOs) are copper-dependent enzymes that cleave polysaccharides through an oxidative mechanism. These enzymes are major contributors to the recycling of carbon in nature and are currently used in the biorefinery industry. LPMOs are commonly used in synergy with cellulases to enhance biomass deconstruction. However, there are few examples of the use of monocomponent LPMOs as a tool for cellulose fibrillation. In this work, we took advantage of the LPMO action to facilitate disruption of wood cellulose fibers as a strategy to produce nanofibrillated cellulose (NFC). RESULTS: The fungal LPMO from AA9 family (PaLPMO9E) was used in this study as it displays high specificity toward cellulose and its recombinant production in bioreactor is easily upscalable. The treatment of birchwood fibers with PaLPMO9E resulted in the release of a mixture of C1-oxidized oligosaccharides without any apparent modification in fiber morphology and dimensions. The subsequent mechanical shearing disintegrated the LPMO-pretreated samples yielding nanoscale cellulose elements. Their gel-like aspect and nanometric dimensions demonstrated that LPMOs disrupt the cellulose structure and facilitate the production of NFC. CONCLUSIONS: This study demonstrates the potential use of LPMOs as a pretreatment in the NFC production process. LPMOs weaken fiber cohesion and facilitate fiber disruption while maintaining the crystallinity of cellulose.
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Villares, A.; Moreau, C.; Bennati-Granier, C.; Garajova, S.; Foucat, L.; Falourd, X.; Saake, B.; Berrin, J. G.; Cathala, B. Lytic polysaccharide monooxygenases disrupt the cellulose fibers structure. Sci. Rep. 2017, 7, 40262, DOI: 10.1038/srep40262
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Lytic polysaccharide monooxygenases disrupt the cellulose fibers structure
Villares, Ana; Moreau, Celine; Bennati-Granier, Chloe; Garajova, Sona; Foucat, Loic; Falourd, Xavier; Saake, Bodo; Berrin, Jean-Guy; Cathala, Bernard
Scientific Reports (2017), 7 (), 40262CODEN: SRCEC3; ISSN:2045-2322. (Nature Publishing Group)
Lytic polysaccharide monooxygenases (LPMOs) are a class of powerful oxidative enzymes that breakdown recalcitrant polysaccharides such as cellulose. Here we investigate the action of LPMOs on cellulose fibers. After enzymic treatment and dispersion, LPMO-treated fibers show intense fibrillation. Cellulose structure modifications visualized at different scales indicate that LPMO creates nicking points that trigger the disintegration of the cellulose fibrillar structure with rupture of chains and release of elementary nanofibrils. Investigation of LPMO action using solid-state NMR provides direct evidence of modification of accessible and inaccessible surfaces surrounding the cryst. core of the fibrils. The chains breakage likely induces modifications of the cellulose network and weakens fibers cohesion promoting their disruption. Besides the formation of new initiation sites for conventional cellulases, this work provides the first evidence of the direct oxidative action of LPMOs with the mech. weakening of the cellulose ultrastructure. LPMOs can be viewed as promising biocatalysts for enzymic modification or degrdn. of cellulose fibers.
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Koskela, S.; Wang, S.; Xu, D.; Yang, X.; Li, K.; Berglund, L.; McKee, L. S.; Bulone, V.; Zhou, Q. Lytic polysaccharide monooxygenase (LPMO) mediated production of ultra-fine cellulose nanofibres from delignified softwood fibres. Green Chem. 2019, 21, 5924– 5933, DOI: 10.1039/C9GC02808K
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Lytic polysaccharide monooxygenase (LPMO) mediated production of ultra-fine cellulose nanofibres from delignified softwood fibres
Koskela, Salla; Wang, Shennan; Xu, Dingfeng; Yang, Xuan; Li, Kai; Berglund, Lars A.; McKee, Lauren S.; Bulone, Vincent; Zhou, Qi
Green Chemistry (2019), 21 (21), 5924-5933CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
The prodn. of cellulose nanofibres (CNFs) typically requires harsh chem. and strong mech. fibrillation, both of which have neg. environmental impacts. A possible soln. is offered by lytic polysaccharide monooxygenases (LPMOs), oxidative enzymes that boost cellulose fibrillation. Although the role of LPMOs in oxidative modification of cellulosic substrates is rather well established, their use in the prodn. of cellulose nanomaterials is not fully explored, and the effect of the carbohydrate-binding module (CBM) on nanofibrillation has not yet been reported. Herein, we studied the activity of two LPMOs, one of which was appended to a CBM, on delignified softwood fibers for green and energy-efficient prodn. of CNFs. The CNFs were used to prep. cellulose nanopapers, and the structure and properties of both nanofibres and nanopapers were detd. Both enzymes were able to facilitate nanocellulose fibrillation and increase the colloidal stability of the produced CNFs. However, the CBM-lacking LPMO was more efficient in introducing carboxyl groups (0.53 mmol g-1) on the cellulose fiber surfaces and releasing CNFs with a thinner width (4.3 ± 1.5 nm) from delignified spruce fibers than the modular LPMO (carboxylate content of 0.38 mmol g-1 and nanofibre width of 6.7 ± 2.5 nm) through LPMO-pretreatment followed by mild homogenization. The prepd. nanopapers showed improved mech. properties (tensile strength of 262 MPa and modulus of 16.2 GPa) compared to those obtained by conventional CNF prepn. methods, demonstrating the potential of LPMOs as green alternatives for cellulose nanomaterial prepn.
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Spangler, D.; Rothenburger, S.; Nguyen, K.; Jampani, H.; Weiss, S.; Bhende, S. In vitro antimicrobial activity of oxidized regenerated cellulose against antibiotic-resistant microorganisms. Surg. Infect. (Larchmt) 2003, 4, 255– 262, DOI: 10.1089/109629603322419599
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In vitro antimicrobial activity of oxidized regenerated cellulose against antibiotic-resistant microorganisms
Spangler Daniel; Rothenburger Stephen; Nguyen Kien; Jampani Hanuman; Weiss Scott; Bhende Shubhangi
Surgical infections (2003), 4 (3), 255-62 ISSN:1096-2964.
BACKGROUND: The emergence of multi-drug resistant microorganisms presents a critical problem for patients undergoing surgery. Acidic pH, which is produced by oxidized regenerated cellulose (ORC), is a broad-spectrum physiological detriment to survival of microorganisms known to cause surgical infections. The purpose of this study was to examine the antimicrobial effect of ORC against antibiotic-resistant organisms. METHODS: ORC products were challenged with ATCC reference strains and clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant Staphylococcus epidermidis (MRSE), vancomycin-resistant Enterococcus (VRE), penicillin-resistant Streptococcus pneumoniae (PRSP), and non-resistant ATCC strains of S. aureus and Pseudomonas aeruginosa. Samples of three ORC products (SURGICEL absorbable hemostat, SURGICEL Fibrillar absorbable hemostat, and SURGICEL NU-KNIT absorbable hemostat and identified, respectively, as ORC-R, ORC-F, and ORC-N for this study) were inoculated with challenge organisms in nutrient broth to produce a weight to volume ratio of 15 mg ORC/mL. Plate counts were performed at 0, 1, 6, and 24 h. RESULTS: Antimicrobial activity was seen with all three ORC products against the challenge organisms. Data indicate that antibiotic-resistant microorganisms remain susceptible to the antimicrobial activity of ORC. In testing with nine of 10 bacteria, including four antibiotic-resistant clinical isolates (VRE, MRSA, and PRSP) three-log or greater reductions were seen at 24-h exposure. One ATCC strain of VRE demonstrated some level of resistance to the acidic pH effect. ORC-N showed a three-log reduction with this organism, whereas the reductions with ORC-R and ORC-F were less than one log. CONCLUSION: Since low pH affects a relatively broad-spectrum of bacteria and does not act in a mechanism-specific manner, as do antibiotics, antibiotic-resistant strains of bacteria are unlikely to resist the ORC pH effect. Results of this in vitro assessment support the hypothesis that the antimicrobial activity of ORC is effective against antibiotic-resistant microorganisms.
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Wohlhauser, S.; Delepierre, G.; Labet, M.; Morandi, G.; Thielemans, W.; Weder, C.; Zoppe, J. O. Grafting polymers from cellulose nanocrystals: synthesis, properties and applications. Macromolecules 2018, 51, 6157– 6189, DOI: 10.1021/acs.macromol.8b00733
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Grafting Polymers from Cellulose Nanocrystals: Synthesis, Properties, and Applications
Wohlhauser, Sandra; Delepierre, Gwendoline; Labet, Marianne; Morandi, Gaelle; Thielemans, Wim; Weder, Christoph; Zoppe, Justin O.
Macromolecules (Washington, DC, United States) (2018), 51 (16), 6157-6189CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
Over the past 10 years, the grafting of polymers from the surface of cellulose nanocrystals (CNCs) has gained substantial interest in both academia and industry due to the rapidly growing no. of potential applications of surface-modified CNCs, which range from building blocks in nanocomposites and responsive nanomaterials to antimicrobial agents. CNCs are rod-like nanoparticles that can be isolated from renewable biosources and which exhibit high crystallinity, tunable aspect ratio, high stiffness, and strength. Upon drying, the abundance of surface hydroxyl groups often leads to a degree of irreversible aggregation, as a result of strong hydrogen bonding. Moreover, their relatively hydrophilic character renders CNCs incompatible with hydrophobic media, e.g., nonpolar solvents and polyolefin matrixes. By grafting macromols. from their surface, CNCs can be imparted with surface characteristics and other physicochem. properties that are reminiscent of the grafted polymer. This has allowed the design of nanoscale building blocks whose readily tunable properties are useful for the formation of both colloidal dispersions and solid state materials. In this Perspective, we provide an overview of the morphol. and surface chem. of CNCs and detail various techniques to manipulate their surface chem. via polymer grafting from approaches. Moreover, we explore the most common polymn. techniques that are used to graft polymers from the surface and reducing end groups of CNCs, including surface-initiated ring-opening polymn. (SI-ROP), surface-initiated free (SI-FRP), and controlled (SI-CRP) radical polymn. Finally, we provide insights into some of the emerging applications and conclude with an outlook of future work that would benefit the field.
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Quintana, E.; Roncero, M. B.; Vidal, T.; Valls, C. Cellulose oxidation by Laccase-TEMPO treatments. Carbohydr. Polym. 2017, 157, 1488– 1495, DOI: 10.1016/j.carbpol.2016.11.033
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Cellulose oxidation by Laccase-TEMPO treatments
Quintana, Elisabet; Roncero, M. Blanca; Vidal, Teresa; Valls, Cristina
Carbohydrate Polymers (2017), 157 (), 1488-1495CODEN: CAPOD8; ISSN:0144-8617. (Elsevier Ltd.)
In this work, laccase-TEMPO (Lac-T) treatments were applied to bleached com. dissolving pulp in order to introduce carbonyl and carboxyl groups, which were found to improve dry and wet strength-related properties. Also the soly. behavior towards xanthate reactions was assessed. The effect of a refining step (R) before the oxidative treatment, the absence or presence of oxygen pressure, TEMPO dose (2 or 8% oven dried pulp) and reaction time (8 or 20 h) were thoroughly examd. Treatments conducted in the presence of oxygen pressure exhibited greater amt. of functional groups. Introducing a pre-refining treatment resulted in similar functional groups but higher wet strength was achieved. Specifically, a high W/D strength ratio was obsd., indicating that wet strength-related property was satisfactorily developed. Besides the fact that all Lac-T treatments caused severe cellulose degrdn., no fiber strength loss was detected. In fact, all oxidized samples presented higher Wet Zero-Span Tensile Strength, mainly in R+ Lac-T (O2) sample, which suggested the formation of hemiacetal linkages between the new introduced aldehyde groups and available free hydroxyl groups resulting from fibrillation.
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Vaaje-Kolstad, G.; Forsberg, Z.; Loose, J. S.; Bissaro, B.; Eijsink, V. G. Structural diversity of lytic polysaccharide monooxygenases. Curr. Opin. Struct. Biol. 2017, 44, 67– 76, DOI: 10.1016/j.sbi.2016.12.012
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Structural diversity of lytic polysaccharide monooxygenases
Vaaje-Kolstad, Gustav; Forsberg, Zarah; Loose, Jennifer S. M.; Bissaro, Bastien; Eijsink, Vincent G. H.
Current Opinion in Structural Biology (2017), 44 (), 67-76CODEN: COSBEF; ISSN:0959-440X. (Elsevier Ltd.)
A review. Lytic polysaccharide monooxygenases (LPMOs) catalyze the oxidative cleavage of glycosidic bonds and represent a promising resource for development of industrial enzyme cocktails for biomass processing. LPMOs show high sequence and modular diversity and are known, so far, to cleave insol. substrates such as cellulose, chitin and starch, as well as hemicelluloses such as beta-glucan, xyloglucan and xylan. All LPMOs share a catalytic histidine brace motif to bind copper, but differ strongly when it comes to the nature and arrangement of residues on the substrate-binding surface. In recent years, the no. of available LPMO structures has increased rapidly, including the first structure of an enzyme-substrate complex. The insights gained from these structures is reviewed below.
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Wang, D.; Li, J.; Salazar-Alvarez, G.; McKee, L. S.; Srivastava, V.; Sellberg, J. A.; Bulome, V.; Hsieh, Y. S. Y. Production of functionalised chitins assisted by fungal lytic polysaccharide monooxygenase. Green Chem. 2018, 20, 2091– 2100, DOI: 10.1039/C8GC00422F
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Production of functionalised chitins assisted by fungal lytic polysaccharide monooxygenase
Wang, Damao; Li, Jing; Salazar-Alvarez, German; McKee, Lauren S.; Srivastava, Vaibhav; Sellberg, Jonas A.; Bulone, Vincent; Hsieh, Yves S. Y.
Green Chemistry (2018), 20 (9), 2091-2100CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
The gene CCT67099 from Fusarium fujikuroi was shown to encode a novel enzyme from the Lytic Polysaccharide Monooxygenase (LPMO) Family AA11. The gene was expressed and a truncated version of the enzyme, designated as FfAA11, was purified from the periplasmic space of Escherichia coli cells at high yield. FfAA11 exhibited oxidative activity against α- and β-chitins, as well as lobster shells. Under optimized conditions, FfAA11 introduced 35 nmol of carboxylate (COO-) moieties per mg of α-chitin. These carboxylate groups were introduced onto the chitin surface under mild enzymic oxidn. conditions in an aq. soln. without changes to the crystallinity of the chitin fibers. FfAA11 was also combined with a simple and environmentally friendly chem. method that transforms recalcitrant chitins into desirable functionalised (nano)materials. The use of ethyl(hydroxyimino)cyanoacetate (Oxyma)-assisted click chem. allowed the rapid modification of the surface of FfAA11-oxidized chitins, with a fluorescent probe, a peptide, and gold nanoparticles. The chem. steps performed, including the FfAA11 oxidase treatment and surface chem. modification, were achieved without the prodn. of any toxic byproducts or waste org. solvents. This approach represents a novel method for the greener prodn. of chitin-based biomaterials.
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Valls, C.; Pastor, F. I. J.; Roncero, M. B.; Vidal, T.; Diaz, P.; Martinez, J.; Valenzuela, S. V. Assessing the enzymatic effects of cellulases and LPMO in improving mechanical fibrillation of cotton linters. Biotechnol. Biofuels 2019, 12, 161, DOI: 10.1186/s13068-019-1502-z
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Assessing the enzymatic effects of cellulases and LPMO in improving mechanical fibrillation of cotton linters
Valls Cristina; Pastor F I Javier; Diaz Pilar; Martinez Josefina; Valenzuela Susana V; Valls Cristina; Roncero M Blanca; Vidal Teresa
Biotechnology for biofuels (2019), 12 (), 161 ISSN:1754-6834.
BACKGROUND: The increasing interest in replacing petroleum-based products by more sustainable materials in the packaging sector gives relevance to cellulose as a biodegradable natural resource. Moreover, its properties can be modified physically, chemically or biotechnologically in order to obtain new bioproducts. Refined cotton linters with high cellulose content were treated with hydrolytic (cellulases) and oxidative (LPMO and Laccase_Tempo) enzymes to evaluate their effect on fibre properties and in improving mechanical fibrillation. RESULTS: Cellulases released cellooligosaccharides, reducing fibre length and partially degrading cellulose. They also improved mechanical fibrillation yielding up to 18% of nanofibrillated cellulose (NFC). LPMO introduced a slight amount of COOH groups in cellulose fibres, releasing cellobionic acid to the effluents. The action of cellulases was improved after LPMO treatment; however, the COOH groups created disappeared from fibres. After mechanical fibrillation of LPMO-cellulase-treated cotton linters a 23% yield of NFC was obtained. Laccase_Tempo treatment also introduced COOH groups in cellulose fibres from cotton, yielding 10% of NFC. Degree of polymerization was reduced by Laccase_Tempo, while LPMO treatment did not significantly affect it but produced a higher reduction in fibre length. The combined treatment with LPMO and cellulase provided films with higher transparency (86%), crystallinity (92%), smoothness and improved barrier properties to air and water than films casted from non-treated linters and from commercial NFC. CONCLUSIONS: The combined enzymatic treatment with LPMO and cellulases boosted mechanical fibrillation of cotton linters, improving the NFC production and providing bioproducts with high transparency and high barrier properties.
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Hrůzová, K.; Matsakas, L.; Karnaouri, A.; Norén, F.; Rova, U.; Christakopoulos, P. Second-generation biofuel production from the marine filter feeder Ciona intestinalis. ACS Sustainable Chem. Eng. 2020, 8, 8373– 8380, DOI: 10.1021/acssuschemeng.0c02417
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Second-Generation Biofuel Production from the Marine Filter Feeder Ciona intestinalis
Hruzova, Katerina; Matsakas, Leonidas; Karnaouri, Anthi; Noren, Fredrik; Rova, Ulrika; Christakopoulos, Paul
ACS Sustainable Chemistry & Engineering (2020), 8 (22), 8373-8380CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)
Biofuels are essential for transitioning to a sustainable society. This switch can be achieved by introducing novel feedstocks and technologies for efficient and economically feasible biofuel prodn. Second-generation biofuels are particularly advantageous, as they are produced from nonedible lignocellulosic biomass derived primarily from agricultural byproducts. Ciona intestinalis, a marine filter feeder, is cultivated to produce fish feed from the invertebrate's inner tissue body. This process generates also vast amts. of a renewable side stream, namely the tunicate's external cellulose-rich tunic. The aim of the present study was to evaluate the potential of the C. intestinalis tunic as a novel feedstock for bioethanol prodn. For this purpose, organosolv fractionation of the tunic was optimized to increase cellulose content. Enzymic saccharification of the pretreated biomass was assessed to identify the most promising materials, which were subsequently utilized as carbon source in fermn. trials. Under optimal conditions, a titer of 38.7 g/L of ethanol, with a yield of 78.3% of the max. theor., was achieved. To the best of our knowledge, this is the first report whereby organosolv pretreated tunic biomass is valorized toward bioethanol prodn.; the current work paves the way for incorporating tunicates in bioconversion processes for the generation of biofuels and other biobased chems. The tunic of Ciona intestinalis is a cellulose-rich waste stream, which represents a promising feedstock for second-generation bioethanol prodn.
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Sluiter, J. B.; Ruiz, R. O.; Scarlata, C. J.; Sluiter, A. D.; Templeton, D. W. Compositional analysis of lignocellulosic feedstocks. 1. Review and description of methods. J. Agric. Food Chem. 2010, 58, 9043– 9053, DOI: 10.1021/jf1008023
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Compositional Analysis of Lignocellulosic Feedstocks. 1. Review and Description of Methods
Sluiter, Justin B.; Ruiz, Raymond O.; Scarlata, Christopher J.; Sluiter, Amie D.; Templeton, David W.
Journal of Agricultural and Food Chemistry (2010), 58 (16), 9043-9053CODEN: JAFCAU; ISSN:0021-8561. (American Chemical Society)
A review. As interest in lignocellulosic biomass feedstocks for conversion into transportation fuels grows, the summative compositional anal. of biomass, or plant-derived material, becomes ever more important. The sulfuric acid hydrolysis of biomass has been used to measure lignin and structural carbohydrate content for more than 100 years. Researchers have applied these methods to measure the lignin and structural carbohydrate contents of woody materials, est. the nutritional value of animal feed, analyze the dietary fiber content of human food, compare potential biofuels feedstocks, and measure the efficiency of biomass-to-biofuels processes. The purpose of this paper is to review the history and lineage of biomass compositional anal. methods based on a sulfuric acid hydrolysis. These methods have become the de facto procedure for biomass compositional anal. The paper traces changes to the biomass compositional anal. methods through time to the biomass methods currently used at the National Renewable Energy Lab. (NREL). The current suite of lab. anal. procedures (LAPs) offered by NREL is described, including an overview of the procedures and methodologies and some common pitfalls. Suggestions are made for continuing improvement to the suite of analyses.
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Karnaouri, A.; Muraleedharan, M. N.; Dimarogona, M.; Topakas, E.; Rova, U.; Sandgren, M.; Christakopoulos, P. Recombinant expression of thermostable processive MtEG5 endoglucanase and its synergism with MtLPMO from Myceliophthora thermophila during the hydrolysis of lignocellulosic substrates. Biotechnol. Biofuels 2017, 10, 126, DOI: 10.1186/s13068-017-0813-1
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Recombinant expression of thermostable processive MtEG5 endoglucanase and its synergism with MtLPMO from Myceliophthora thermophila during the hydrolysis of lignocellulosic substrates
Karnaouri, Anthi; Muraleedharan, Madhu Nair; Dimarogona, Maria; Topakas, Evangelos; Rova, Ulrika; Sandgren, Mats; Christakopoulos, Paul
Biotechnology for Biofuels (2017), 10 (), 126/1-126/17CODEN: BBIIFL; ISSN:1754-6834. (BioMed Central Ltd.)
Background: Filamentous fungi are among the most powerful cellulolytic organisms in terrestrial ecosystems. To perform the degrdn. of lignocellulosic substrates, these microorganisms employ both hydrolytic and oxidative mechanisms that involve the secretion and synergism of a wide variety of enzymes. Interactions between these enzymes occur on the level of saccharification, i.e., the release of neutral and oxidized products, but sometimes also reflected in the substrate liquefaction. Although the synergism regarding the yield of neutral sugars has been extensively studied, further studies should focus on the oxidized sugars, as well as the effect of enzyme combinations on the viscosity properties of the substrates. Results: In the present study, the heterologous expression of an endoglucanase (EG) and its combined activity together with a lytic polysaccharide monooxygenase (LPMO), both from the thermophilic fungus Myceliophthora thermophila, are described. The EG gene, belonging to the glycoside hydrolase family 5, was functionally expressed in the methylotrophic yeast Pichia pastoris. The produced MtEG5A (75 kDa) featured remarkable thermal stability and showed high specific activity on microcryst. cellulose compared to CMC, which is indicative of its processivity properties. The enzyme was capable of releasing high amts. of cellobiose from wheat straw, birch, and spruce biomass. Addn. of MtLPMO9 together with MtEG5A showed enhanced enzymic hydrolysis yields against regenerated amorphous cellulose (PASC) by improving the release not only of the neutral but also of the oxidized sugars. Assessment of activity of MtEG5A on the redn. of viscosity of PASC and pretreated wheat straw using dynamic viscosity measurements revealed that the enzyme is able to perform liquefaction of the model substrate and the natural lignocellulosic material, while when added together with MtLPMO9, no further synergistic effect was obsd. Conclusions: The endoglucanase MtEG5A from the thermophilic fungus M. thermophila exhibited excellent properties that render it a suitable candidate for use in biotechnol. applications. Its strong synergism with LPMO was reflected in sugars release, but not in substrate viscosity redn. Based on the level of oxidative sugar formation, this is the first indication of synergy between LPMO and EG reported.
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Lowry, O. H.; Rosebrough, N. J.; Lewis Farr, A.; Randall, R. J. Protein Measurement with the Folin phenol reagent. J. Biol. Chem. 1951, 193, 265– 275
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Protein measurement with the Folin phenol reagent
Lowry, Oliver H.; Rosebrough, Nira J.; Farr, A. Lewis; Randall, Rose J.
Journal of Biological Chemistry (1951), 193 (), 265-75CODEN: JBCHA3; ISSN:0021-9258.
cf. C.A. 41, 1271h. Proteins were detd. with the Folin phenol reagent after alk. Cu treatment. The method is as sensitive as with Nessler reagent, yet requires no digestion. It is 10-20 times more sensitive than detn. of the ultraviolet absorption at λ = 280 mμ and is more specific. It is several fold more sensitive than the ninhydrin reaction and 100 times more sensitive than the biuret reaction. Two major disadvantages are: the amt. of color varies with different proteins; the color is not strictly proportional to concn. Few substances cause serious interference. Uric acid, guanine, and xanthine react with Folin reagent. The method is useful for following enzyme fractionation, detg. mixed tissue proteins, detn. of very small amts. of protein, or detg. highly dild. protein, or protein in colored solns. or in the presence of N-contg. material.
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Schulz, B. L.; Packer, N. H.; Karlsson, N. G. Small-scale analysis of O-linked oligosaccharides from glycoproteins and mucins separated by gel electrophoresis. Anal. Chem. 2002, 74, 6088– 6097, DOI: 10.1021/ac025890a
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Small-scale analysis of O-linked oligosaccharides from glycoproteins and mucins separated by gel electrophoresis
Schulz, Benjamin L.; Packer, Nicolle H.; Karlsson, Niclas G.
Analytical Chemistry (2002), 74 (23), 6088-6097CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
A technique with subpicomolar sensitivity was developed for analyzing O-linked oligosaccharides released from glycoproteins sepd. by gel electrophoresis. The protocol involves gel electrophoresis, electroblotting to poly(vinylidene fluoride) membrane, reductive β-elimination, and anal. of released oligosaccharides by liq. chromatog. coupled to neg. ion electrospray mass spectrometry. It was also found that N-linked oligosaccharides could be recovered under the same conditions, found both as free oligosaccharides and as distinct glycopeptides created from reductive cleavage of the protein backbone, giving some information on site-specific glycosylation. The method was used to demonstrate that the difference between human α-2HS-glycoprotein isoforms sepd. by 2D-gel electrophoresis was partially due to sialylation of both O-linked and N-linked oligosaccharides. It was also shown that both acidic and neutral oligosaccharides could be recovered and analyzed simultaneously from high mol. mass (200 000-5 000 000 Da) highly glycosylated mucin glycoproteins collected from small intestine and saliva and sepd. by SDS-agarose/polyacrylamide composite gels. Mass spectrometric data not only gave information about the mass distribution of the heterogeneous mixts. of oligosaccharides from [M - xH]x- ions but also gave information about the isomeric heterogeneity of the oligosaccharides from their resoln. by porous graphitized carbon chromatog. Tandem mass spectrometry was explored as a technique for distinguishing between oligosaccharide isomers with different sequences and also between oligosaccharides with the same sequence but with different linkage configurations.
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Bondeson, D.; Mathew, A.; Oksman, K. Optimization of the isolation of nanocrystals from microcrystalline cellulose by acid hydrolysis. Cellulose 2006, 13, 171– 180, DOI: 10.1007/s10570-006-9061-4
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Optimization of the isolation of nanocrystals from microcrystalline cellulose by acid hydrolysis
Bondeson, Daniel; Mathew, Aji; Oksman, Kristiina
Cellulose (Dordrecht, Netherlands) (2006), 13 (2), 171-180CODEN: CELLE8; ISSN:0969-0239. (Springer)
The objective of this work was to find a rapid, high-yield process to obtain an aq. stable colloid suspension of cellulose nanocrystals/whiskers. Large quantities are required since these whiskers are designed to be extruded into polymers in the prodn. of nano-biocomposites. Microcryst. cellulose (MCC), derived from Norway spruce (Picea abies), was used as the starting material. The processing parameters have been optimized by using response surface methodol. The factors that varied during the process were the concn. of MCC and sulfuric acid, the hydrolysis time and temp., and the ultrasonic treatment time. Responses measured were the median size of the cellulose particles/whiskers and yield. The surface charge as calcd. from conductometric titrn., microscopic examns. (optical and transmission electron microscopy), and observation of birefringence were also investigated in order to det. the outcome (efficiency) of the process. With a sulfuric acid concn. of 63.5% (wt./wt.), it was possible to obtain cellulose nanocrystals/whiskers with a length between 200 and 400 nm and a width less than 10 nm in approx. 2 h with a yield of 30% (of initial wt.).
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Klarhöfer, L.; Roos, B.; Viöl, W.; Höfft, O.; Dieckhoff, S.; Kempter, V.; Maus-Friedrichs, W. Valence band spectroscopy on lignin. Holzforschung 2008, 62. DOI: 10.1515/HF.2008.116
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Krischok, S.; Höfft, O.; Günster, J.; Stultz, J.; Goodman, D. W.; Kempter, V. H2O interaction with bare and Li-precovered TiO2: Studies with electron spectroscopies (MIES and UPS (HeI and II)). Surf. Sci. 2001, 495, 8– 18, DOI: 10.1016/S0039-6028(01)01570-9
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H2O interaction with bare and Li-precovered TiO2. Studies with electron spectroscopies (MIES and UPS(HeI and II))
Krischok, S.; Hofft, O.; Gunster, J.; Stultz, J.; Goodman, D. W.; Kempter, V.
Surface Science (2001), 495 (1-2), 8-18CODEN: SUSCAS; ISSN:0039-6028. (Elsevier Science B.V.)
TiO2(1 1 0) single crystals and TiO2 thin films on Mo(1 1 0), bare and precovered by Li atoms, were exposed to water at 120 K. During the adsorption process metastable impact electron spectroscopy (MIES) and UV photoemission spectroscopy (UPS)(HeI and II) spectra were collected in situ. Spectroscopic and temp.-programmed desorption data were obtained during the annealing of water multilayers grown at 120 K. For the adsorption on the bare TiO2 surface we conclude that an initial dissociative adsorption at defect sites is followed by mol. adsorption up to multilayer formation. From the exposure dependence of the MIES and UPS signals we conclude that, even before the completion of the first adlayer, no isolated water mols. are sampled, and strong lateral interaction between adjacent adsorbates stabilizes mol. water.On TiO2(1 1 0), precovered by about 1 ML of Li atoms, water is adsorbed dissociatively both at 120 K and at room temp. until the first, mixed layer consisting of Li and OH species, is completed. On top of the first layer addnl. water is adsorbed molecularly. Annealing expts. show that the first layer remains intact when the second layer forms.
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Hercules, D. M.; Cox, L. E.; Onisick, S.; Nichols, G. D.; Carver, J. C. Electron spectroscopy (ESCA). Use for trace analysis. Anal. Chem. 1973, 45, 1973– 1975, DOI: 10.1021/ac60333a037
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Electron spectroscopy (ESCA). Use for trace analysis
Hercules, David M.; Cox, Lawrence E.; Onisick, Stephen; Nichols, Gary D.; Carver, James C.
Analytical Chemistry (1973), 45 (11), 1973-5CODEN: ANCHAM; ISSN:0003-2700.
For detn. by ESCA, trace metals were collected by passing sample solns. through glass fiber disks coated with dithiocarbamate chelating groups. To prep. the disks, glass fibers were treated with 4% Dow-Corning Z-6020 silylizing reagent. For conversion to dithiocarbamate, the silylized glass was refluxed in 1M NaOH-1.5M CS2 in EtOH. Detection limits were ∼10 ppb for Pb, Ca, Tl, and Hg. For quant. anal., an internal std. metal can be added to the sample soln. and collected on the disks.
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Nam, S.; French, A. D.; Condon, B. D.; Concha, M. Segal crystallinity index revisited by the simulation of X-ray diffraction patterns of cotton cellulose Iβ and cellulose II. Carbohydr. Polym. 2016, 135, 1– 9, DOI: 10.1016/j.carbpol.2015.08.035
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Segal crystallinity index revisited by the simulation of X-ray diffraction patterns of cotton cellulose Iβ and cellulose II
Nam, Sunghyun; French, Alfred D.; Condon, Brian D.; Concha, Monica
Carbohydrate Polymers (2016), 135 (), 1-9CODEN: CAPOD8; ISSN:0144-8617. (Elsevier Ltd.)
The Segal method ests. the amorphous fraction of cellulose Iβ materials simply based on intensity at 18° 2θ in an X-ray diffraction pattern and was extended to cellulose II using 16° 2θ intensity. To address the dependency of Segal amorphous intensity on crystal size, cellulose polymorph, and the degree of polymorphic conversion, we simulated the diffraction patterns of cotton celluloses (Iβ and II) and compared the simulated amorphous fractions with the Segal values. The diffraction patterns of control and mercerized cottons, resp., were simulated with perfect crystals of cellulose Iβ (1.54° FWHM) and cellulose II (2.30° FWHM) as well as 10% and 35% amorphous celluloses. Their Segal amorphous fractions were 15% and 31%, resp. The higher Segal amorphous fraction for control cotton was attributed to the peak overlap. Although the amorphous fraction was set in the simulation, the peak overlap induced by the increase of FWHM further enhanced the Segal amorphous intensity of cellulose Iβ. For cellulose II, the effect of peak overlap was smaller; however the lower reflection of the amorphous cellulose scattering in its Segal amorphous location resulted in smaller Segal amorphous fractions. Despite this underestimation, the relatively good agreement of the Segal method with the simulation for mercerized cotton was attributed to the incomplete conversion to cellulose II. The (1 -1 0) and (1 1 0) peaks of cellulose Iβ remained near the Segal amorphous location of cellulose II for blends of control and mercerized cotton fibers.
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Thoresen, P. P.; Matsakas, L.; Rova, U.; Christakopoulos, P. Recent advances in organosolv fractionation: Towards biomass fractionation technology of the future. Bioresour. Technol. 2020, 306, 123189, DOI: 10.1016/j.biortech.2020.123189
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Recent advances in organosolv fractionation: Towards biomass fractionation technology of the future
Thoresen, Petter Paulsen; Matsakas, Leonidas; Rova, Ulrika; Christakopoulos, Paul
Bioresource Technology (2020), 306 (), 123189CODEN: BIRTEB; ISSN:0960-8524. (Elsevier Ltd.)
A review. Organosolv treatment is among the most promising strategies for valorising lignocellulosic biomass and could facilitate the transition towards enhanced utilization of renewable feedstocks. However, issues such as inefficient solvent recycle and fractionation has to be overcome. The present review aims to address these issues and discuss the role of the components present during organosolv treatment and their influence on the overall process. Thus, the review focuses not only on how the choice of solvent and catalyst affects lignocellulosic fractionation, but also on how the choice of treatment liquor influences the possibility for solvent recycling and product isolation. Several org. solvents have been investigated in combination with water and acid/base catalysts; however, the lack of a holistic approach often compromises the performance of the different operational units. Thus, an economically viable organosolv process should optimize biomass fractionation, product isolation, and solvent recycling.
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Kalogiannis, K. G.; Karnaouri, A.; Michailof, C.; Tzika, A. M.; Asimakopoulou, G.; Topakas, E.; Lappas, A. A. OxiOrganosolv: A novel acid free oxidative organosolv fractionation for lignocellulose fine sugar streams. Bioresour. Technol. 2020, 313, 123599, DOI: 10.1016/j.biortech.2020.123599
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OxiOrganosolv: A novel acid free oxidative organosolv fractionation for lignocellulose fine sugar streams
Kalogiannis, Konstantinos G.; Karnaouri, Anthi; Michailof, Chrysoula; Tzika, Anna Maria; Asimakopoulou, Georgia; Topakas, Evangelos; Lappas, Angelos A.
Bioresource Technology (2020), 313 (), 123599CODEN: BIRTEB; ISSN:0960-8524. (Elsevier Ltd.)
The valorization of lignocellulosic biomass towards the prodn. of value-added products requires an efficient pretreatment/fractionation step. In this work we present a novel, acid-free, mildly oxidative organosolv delignification process -OxiOrganosolv- which employs oxygen gas to depolymerize and remove lignin. The results demonstrate that the OxiOrganosolv process achieved lignin removal as high as 97% in a single stage, with a variety of solvents; it was also efficient in delignifying both beechwood (hardwood) and pine (softwood), a task in which organosolv pretreatments have failed in the past. Minimal amts. of sugar degrdn. products were detected, while cellulose recovery was ∼100% in the solid pulp. Enzymic hydrolysis of pulps showed >80 wt% cellulose conversion to glucose. Overall, the OxiOrganosolv pretreatment has significant advantages, including high delignification efficiency of hardwood and softwood biomass, absence of acid homogeneous catalysis and all corresponding challenges involved, and close to zero losses of sugars to degrdn. products.
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Mantanis, G. I.; Young, R. A.; Rowell, R. M. Swelling of compressed cellulose fiber webs in organic liquids. Cellulose 1995, 2, 1– 22, DOI: 10.1007/BF00812768
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Swelling of compressed cellulose fiber webs in organic liquids
Mantanis, G. I.; Young, R. A.; Rowell, R. M.
Cellulose (London) (1995), 2 (1), 1-22CODEN: CELLE8; ISSN:0969-0239. (Chapman & Hall)
Max. liq.-holding capacities of various compressed fibers in water and in a series of various org. liqs. were investigated. The max. liq.-holding capacity vs. bulk d. relationships gave polynomial curves, generally with a peak. Good relative correlations for cellulose, compressed fiber pellets and wood were found for the series of liqs. tested. In general, liqs. that swelled wood to a low-to-medium range (≤6%) did not swell appreciably α-cellulose and sulfite pulp, whereas good-to-excellent wood-swelling agents swelled all of the fibers very significantly. Also, the hydrogen-bonding parameter of the swelling liq. was the most important factor. The swelling rate of various compressed fiber systems in org. liqs. was dramatically increased by raising the temp. Activation energies and molar vol. of the swelling liq. were linearly correlated.
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Sannigrahia, P.; Miller, S. J.; Ragauskas, A. J. Effects of organosolv pretreatment and enzymatic hydrolysis on cellulose structure and crystallinity in Loblolly pine. Carbohydr. Res. 2010, 345, 965– 970, DOI: 10.1016/j.carres.2010.02.010
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Levasseur, A.; Drula, E.; Lombard, V.; Coutinho, P. M.; Henrissat, B. Expansion of the enzymatic repertoire of the CAZy database to integrate auxiliary redox enzymes. Biotechnol. Biofuels 2013, 6, 41, DOI: 10.1186/1754-6834-6-41
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Expansion of the enzymatic repertoire of the CAZy database to integrate auxiliary redox enzymes
Levasseur, Anthony; Drula, Elodie; Lombard, Vincent; Coutinho, Pedro M.; Henrissat, Bernard
Biotechnology for Biofuels (2013), 6 (), 41CODEN: BBIIFL; ISSN:1754-6834. (BioMed Central Ltd.)
Background: Since its inception, the carbohydrate-active enzymes database (CAZy;) has described the families of enzymes that cleave or build complex carbohydrates, namely the glycoside hydrolases (GH), the polysaccharide lyases (PL), the carbohydrate esterases (CE), the glycosyltransferases (GT) and their appended non-catalytic carbohydrate-binding modules (CBM). The recent discovery that members of families CBM33 and family GH61 are in fact lytic polysaccharide monooxygenases (LPMO), demands a reclassification of these families into a suitable category. Results: Because lignin is invariably found together with polysaccharides in the plant cell wall and because lignin fragments are likely to act in concert with (LPMO), we have decided to join the families of lignin degrdn. enzymes to the LPMO families and launch a new CAZy class that we name "Auxiliary Activities" in order to accommodate a range of enzyme mechanisms and substrates related to lignocellulose conversion. Comparative analyses of these auxiliary activities in 41 fungal genomes reveal a pertinent division of several fungal groups and subgroups combining their phylogenetic origin and their nutritional mode (white vs. brown rot). Conclusions: The new class introduced in the CAZy database extends the traditional CAZy families, and provides a better coverage of the full extent of the lignocellulose breakdown machinery.
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Silva, C. d. O. G.; Teixeira, T. S.; Rodrigues, K. B.; Souza, A. A.; Monclaro, A. V.; Mendes, T. D. Combination of MALDI-TOF MS and UHPLC-ESI-MS for the characterization of lytic polysaccharide monooxygenase activity. Anal. Methods 2020, 12, 149– 161, DOI: 10.1039/c9ay01774g
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Combination of MALDI-TOF MS and UHPLC-ESI-MS for the characterization of lytic polysaccharide monooxygenase activity
Silva, Caio de Oliveira Gorgulho; Teixeira, Tallyta Santos; Rodrigues, Kelly Barreto; Souza, Amanda Araujo; Monclaro, Antonielle Vieira; Mendes, Thais Demarchi; Ribeiro, Jose Antonio de Aquino; Goncalves de Siqueira, Felix; Favaro, Leia Cecilia de Lima; Abdelnur, Patricia Verardi
Analytical Methods (2020), 12 (2), 149-161CODEN: AMNEGX; ISSN:1759-9679. (Royal Society of Chemistry)
Lytic polysaccharide monooxygenases (LPMOs) are redox enzymes of high biotechnol. interest due to their capacity to degrade recalcitrant polysaccharides, such as cellulose, by an oxidative mechanism. The characterization of LPMOs is challenging since they generate a variety of catalytic products which include native oligosaccharides (non-oxidized) and oligosaccharides oxidized at the reducing end (C1 position), the non-reducing end (C4 position), or both ends, with different ds.p. Moreover, oxidized products exist in equil. with their hydrated forms, which further complicates their identification. The lack of com. anal. stds. for all these possible forms of oxidized oligosaccharides and the low concn. of these products make LPMO functional characterization dependent on advanced mass spectrometry techniques capable of identifying the profile of oxidized products. Here, a new approach for the characterization of cellulose-active LPMOs based on the combination of MALDI-TOF MS and hydrophilic interaction UHPLC-ESI-MS was proposed and optimized. The LPMO TrAA9A from Trichoderma reesei was used as a model enzyme to develop and test the MS methods. MALDI-TOF MS and UHPLC-ESI-MS methods were both capable of identifying putative C1, C4 and C1/C4 oxidized cello-oligosaccharides as well as their native counterparts generated after cellulose treatment with LPMO, which allows their utilization to characterize type I (C1-oxidizer), type II (C4-oxidizer) and type III (C1- and C4-oxidizer) LPMOs. Moreover, both methods were complementary since MALDI-TOF MS was capable of detecting oligosaccharides with higher ds.p. (DP3-DP10), while UHPLC-ESI-MS allowed the evaluation of smaller oligosaccharides (DP1-DP5). The combined use of both methods offers a comprehensive description of LPMO catalytic products.
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Zhao, Y.; Li, J. Ascidian bioresources: common and variant chemical compositions and exploitation strategy – examples of Halocynthia roretzi, Styela plicata, Ascidia sp. and Ciona intestinalis. Z. Naturforschung C 2016, 71, 165– 180, DOI: 10.1515/znc-2016-0012
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Ascidian bioresources: common and variant chemical compositions and exploitation strategy - examples of Halocynthia roretzi, Styela plicata, Ascidia sp. and Ciona intestinalis
Zhao, Yadong; Li, Jiebing
Zeitschrift fuer Naturforschung, C: Journal of Biosciences (2016), 71 (5-6), 165-180CODEN: ZNCBDA; ISSN:1865-7125. (Walter de Gruyter GmbH)
To explore abundant marine ascidian bioresources, four species from two orders have been compared in their chem. compns. After a universal sepn. of the animal body into two fractions, all tunics have been found rich in carbohydrate contents, while all inner body tissues are richer in proteins. Cellulose is present almost exclusively in the tunics and more in the order Stolidobranchia, while more sulfated polysaccharides are present in Phlebobranchia species. Almost all proteins are collagens with a high essential amino acid index and high delicious amino acid (DAA) content. All fractions also have high contents of good-quality fatty acids and trace minerals but low toxic element contents, with different sterols and glycosaminoglycans. There are species-specific characteristics obsd. for vanadium accumulation and sterol structures which are also meaningful for ascidian chemotaxonomy and resource exploitation. It is suggested that in addn. to the present utilizations of tunics for cellulose prodn. and of some species' inner body tissues as human food, one should explore all species' inner body tissues as human foods and all tunics as food or animal feed with the contained cellulose as dietary fiber. Collagens, sulfated polysaccharides, glycosaminoglycans, sterols and trace elements could be explored as byproducts for, e.g. pharmaceutical and chem. industries.
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Eibinger, M.; Ganner, T.; Bubner, P.; Rošker, S.; Kasciddvgdgracher, D.; Haltrich, D.; Ludwig, R.; Plank, H.; Nidetzky, B. Cellulose surface degradation by a lytic polysaccharide monooxygenase and its effect on cellulase hydrolytic efficiency. J. Biol. Chem. 2014, 289, 35929– 35938, DOI: 10.1074/jbc.M114.602227
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Cellulose surface degradation by a lytic polysaccharide monooxygenase and its effect on cellulase hydrolytic efficiency
Eibinger, Manuel; Ganner, Thomas; Bubner, Patricia; Rosker, Stephanie; Kracher, Daniel; Haltrich, Dietmar; Ludwig, Roland; Plank, Harald; Nidetzky, Bernd
Journal of Biological Chemistry (2014), 289 (52), 35929-35938CODEN: JBCHA3; ISSN:0021-9258. (American Society for Biochemistry and Molecular Biology)
Lytic polysaccharide monooxygenase (LPMO) represents a unique principle of oxidative degrdn. of recalcitrant insol. polysaccharides. Used in combination with hydrolytic enzymes, LPMO appears to constitute a significant factor of the efficiency of enzymic biomass depolymn. LPMO activity on different cellulose substrates has been shown from the slow release of oxidized oligosaccharides into soln., but an immediate and direct demonstration of the enzyme action on the cellulose surface is lacking. The specificity of LPMO for degrading ordered cryst. and unordered amorphous cellulose material of the substrate surface is also unknown. Here, the authors show by fluorescent dye adsorption analyzed with confocal laser scanning microscopy that a LPMO (from Neurospora crassa) introduces carboxyl groups primarily in surface-exposed cryst. areas of the cellulosic substrate. Using time-resolved in situ at. force microscopy (AFM), the authors further demonstrated that cellulose nanofibrils exposed on the surface were degraded into shorter and thinner insol. fragments. Also using AFM, the authors showed that prior action of LPMO enabled cellulases to attack otherwise highly resistant cryst. substrate areas and that it promoted an overall faster and more complete surface degrdn. Overall, this study reveals key characteristics of LPMO action on the cellulose surface and suggests the effects of substrate morphol. on the synergy between LPMO and hydrolytic enzymes in cellulose depolymn.
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Siqueira, P.; Siqueira, É.; De Lima, A. E.; Siqueira, G.; Pinzón-Garcia, A. D.; Lopes, A. P.; Segura, M. E. C.; Isaac, A.; Pereira, F. V.; Botaro, V. R. Three-dimensional stable alginate-nanocellulose gels for biomedical applications: towards tunable mechanical properties and cell growing. Nanomaterials 2019, 9, 78, DOI: 10.3390/nano9010078
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Three-dimensional stable alginate-nanocellulose gels for biomedical applications: towards tunable mechanical properties and cell growing
Siqueira, Priscila; Siqueira, Eder; de Lima, Ana Elza; Siqueira, Gilberto; Pinzon-Garcia, Ana Delia; Lopes, Ana Paula; Segura, Maria Esperanza Cortes; Isaac, Augusta; Pereira, Fabiano Vargas; Botaro, Vagner Roberto
Nanomaterials (2019), 9 (1), 78/1-78/22CODEN: NANOKO; ISSN:2079-4991. (MDPI AG)
Hydrogels have been studied as promising materials in different biomedical applications such as cell culture in tissue engineering or in wound healing. In this work, we synthesized different nanocellulose-alginate hydrogels contg. cellulose nanocrystals, TEMPO-oxidized cellulose nanocrystals (CNCTs), cellulose nanofibers or TEMPO-oxidized cellulose nanofibers (CNFTs). The hydrogels were freeze-dried and named as gels. The nanocelluloses and the gels were characterized by different techniques such as Fourier-transform IR spectroscopy (FTIR), SEM (SEM), transmission electron microscopy (TEM), thermogravimetric anal. (TGA), and dynamic mech. thermal anal. (DMTA), while the biol. features were characterized by cytotoxicity and cell growth assays. The addn. of CNCTs or CNFTs in alginate gels contributed to the formation of porous structure (diam. of pores in the range between 40 and 150μm). TEMPO-oxidized cellulose nanofibers have proven to play a crucial role in improving the dimensional stability of the samples when compared to the pure alginate gels, mainly after a thermal post-treatment of these gels contg. 50 wt of CNFT, which significantly increased the Ca2+ crosslinking d. in the gel structure. The morphol. characteristics, the mech. properties, and the non-cytotoxic behavior of the CNFT-alginate gels improved bioadhesion, growth, and proliferation of the cells onto the gels. Thus, the alginate-nanocellulose gels might find applications in tissue engineering field, as for instance, in tissue repair or wound healing applications.
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Xie, K.; Yu, Y.; Shi, Y. Synthesis and characterization of cellulose/silica hybrid materials with chemical crosslinking. Carbohydr. Polym. 2009, 78, 799– 805, DOI: 10.1016/j.carbpol.2009.06.019
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Synthesis and characterization of cellulose/silica hybrid materials with chemical crosslinking
Xie, Kongliang; Yu, Yanhong; Shi, Yaqi
Carbohydrate Polymers (2009), 78 (4), 799-805CODEN: CAPOD8; ISSN:0144-8617. (Elsevier Ltd.)
The cellulose/silica hybrid biomaterials are prepd. by sol-gel covalent crosslinking process. The tetraethoxysilane (TEOS) as precursor, γ-aminopropyltriethoxylsilane (APTES) as couple agent, and 2,4,6-tri[(2-epihydrin-3-bimethyl-ammonium)propyl]-1,3,5-triazine chloride (Tri-EBAC) as crosslinking agent, are used in the sol-gel crosslinking process. The chem. and morphol. structures of cellulose/silica covalent crosslinking hybrids are investigated with micro-FT-IR spectra, nitrogen element anal., X-ray diffraction, SEM, AFM, and DSC. The results show that the cellulose/silica hybrids form new macromol. structures. In sol-gel process, inorg. particles are dispersed at the nanometer scale in the cellulose host matrix, bounding to the cellulose through covalent bonds. The cellulose/silica covalent crosslinking hybrid can form good and smooth film on the cellulose. The thermal properties of org./inorg. hybrids are improved.
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Bhattacharjee, S. DLS and zeta potential - What they are and what they are not?. J. Controlled Release 2016, 235, 337– 351, DOI: 10.1016/j.jconrel.2016.06.017
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DLS and zeta potential - What they are and what they are not?
Bhattacharjee, Sourav
Journal of Controlled Release (2016), 235 (), 337-351CODEN: JCREEC; ISSN:0168-3659. (Elsevier B.V.)
A review. Adequate characterization of NPs (nanoparticles) is of paramount importance to develop well defined nanoformulations of therapeutic relevance. Detn. of particle size and surface charge of NPs are indispensable for proper characterization of NPs. DLS (dynamic light scattering) and ZP (zeta potential) measurements have gained popularity as simple, easy and reproducible tools to ascertain particle size and surface charge. Unfortunately, on practical grounds plenty of challenges exist regarding these two techniques including inadequate understanding of the operating principles and dealing with crit. issues like sample prepn. and interpretation of the data. As both DLS and ZP have emerged from the realms of phys. colloid chem. - it is difficult for researchers engaged in nanomedicine research to master these two techniques. Addnl., there is little literature available in drug delivery research which offers a simple, concise account on these techniques. This review tries to address this issue while providing the fundamental principles of these techniques, summarizing the core math. principles and offering practical guidelines on tackling commonly encountered problems while running DLS and ZP measurements. Finally, the review tries to analyze the relevance of these two techniques from translatory perspective.
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Johnston, L. J.; Jakubek, Z. J.; Beck, S.; Araki, J.; Cranston, E. D.; Danumah, C.; Fox, D.; Li, H.; Wang, J.; Mester, Z.; Moores, A.; Rabb, S. A.; Murphy, K. E.; Stephan, C. Determination of sulfur and sulfate half-ester content in cellulose nanocrystals: an interlaboratory comparison. Metrologia 2018, 55, 872, DOI: 10.1088/1681-7575/aaeb60
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Determination of sulfur and sulfate half-ester content in cellulose nanocrystals: an interlaboratory comparison
Johnston, Linda J.; Jakubek, Zygmunt J.; Beck, Stephanie; Araki, Jun; Cranston, Emily D.; Danumah, Christophe; Fox, Douglas; Li, Haifeng; Wang, Jun; Mester, Zoltan; Moores, Audrey; Murphy, Karen; Rabb, Savelas A.; Rudie, Alan; Stephan, Chady
Metrologia (2018), 55 (6), 872-882CODEN: MTRGAU; ISSN:1681-7575. (IOP Publishing Ltd.)
Charged functional groups on the surface of cellulose nanocrystals (CNCs) are important for controlling the colloidal stability of suspensions and the interaction of the material with its environment. Quantification of surface groups is therefore an important metric for reproducible prodn. of this nanomaterial. Here we report the results of an inter lab. comparison (ILC) with twelve participants piloted by National Research Council Canada (NRC) that evaluated two methods for detg. the sulfur content for an NRC ref. material (CNCD-1) produced from CNCs extd. by sulfuric acid hydrolysis of wood pulp. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) was used to measure the total sulfur content of CNCs after microwave assisted digestion in strong acid. Conductometric titrn. quantified the neg. charged sulfate half-ester groups on the CNC surface after dialysis and protonation using ion exchange resin. The data was analyzed with an ASTM method that employs h and k statistics to identify data sets for which the lab. mean or std. deviation show excessive variation from the overall mean or std. deviation and the NIST consensus builder (NICOB) engine using the DerSimonian-Laird meta-anal. to det. a consensus est. of the mean and its assocd. measurement uncertainty. The consensus ests. ± uncertainty for total sulfur and sulfate half ester content were (8771 ± 94) mg kg-1 and (252.0 ± 8.2) mmol kg-1, resp. Neither approach identified any outliers in the data sets and the consensus ests. were in agreement with values obtained during certification of the ref. material. The results confirmed that the difference between the sulfur content measured by conductometric titrn. and ICP-OES is larger than the combined 95% expanded uncertainties. The higher sulfur content measured by ICP-OES may reflect the presence of sulfur impurities that are not detected by titrn. Overall the ILC provides validation for the protocols for the two methods and indicates that both are reasonably tolerant of small variations from the protocol. A more reliable method of assessing the titrn. endpoint and a quality control (QC) sample were identified as potential improvements to reduce variability for the conductometric titrn.
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Bennati-Granier, C.; Garajova, S.; Champion, C.; Grisel, S.; Haon, M.; Zhou, S.; Fanuel, M.; Ropartz, D.; Rogniaux, H.; Gimbert, I.; Record, E.; Berrin, J. G. Substrate specificity and regioselectivity of fungal AA9 lytic polysaccharide monooxygenases secreted by Podospora anserina. Biotechnol. Biofuels 2015, 8, 90, DOI: 10.1186/s13068-015-0274-3
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Substrate specificity and regioselectivity of fungal AA9 lytic polysaccharide monooxygenases secreted by Podospora anserina
Bennati-Granier Chloe; Garajova Sona; Champion Charlotte; Grisel Sacha; Haon Mireille; Zhou Simeng; Gimbert Isabelle; Record Eric; Berrin Jean-Guy; Bennati-Granier Chloe; Garajova Sona; Champion Charlotte; Grisel Sacha; Haon Mireille; Zhou Simeng; Gimbert Isabelle; Record Eric; Berrin Jean-Guy; Garajova Sona; Fanuel Mathieu; Ropartz David; Rogniaux Helene
Biotechnology for biofuels (2015), 8 (), 90 ISSN:1754-6834.
BACKGROUND: The understanding of enzymatic polysaccharide degradation has progressed intensely in the past few years with the identification of a new class of fungal-secreted enzymes, the lytic polysaccharide monooxygenases (LPMOs) that enhance cellulose conversion. In the fungal kingdom, saprotrophic fungi display a high number of genes encoding LPMOs from family AA9 but the functional relevance of this redundancy is not fully understood. RESULTS: In this study, we investigated a set of AA9 LPMOs identified in the secretomes of the coprophilous ascomycete Podospora anserina, a biomass degrader of recalcitrant substrates. Their activity was assayed on cellulose in synergy with the cellobiose dehydrogenase from the same organism. We showed that the total release of oxidized oligosaccharides from cellulose was higher for PaLPMO9A, PaLPMO9E, and PaLPMO9H that harbored a carbohydrate-binding module from the family CBM1. Investigation of their regioselective mode of action revealed that PaLPMO9A and PaLPMO9H oxidatively cleaved at both C1 and C4 positions while PaLPMO9E released only C1-oxidized products. Rapid cleavage of cellulose was observed using PaLPMO9H that was the most versatile in terms of substrate specificity as it also displayed activity on cello-oligosaccharides and β-(1,4)-linked hemicellulose polysaccharides (e.g., xyloglucan, glucomannan). CONCLUSIONS: This study provides insights into the mode of cleavage and substrate specificities of fungal AA9 LPMOs that will facilitate their application for the development of future biorefineries.
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Isogai, A.; Saito, T.; Fukuzumi, H. TEMPO-oxidized cellulose nanofibers. Nanoscale 2011, 3, 71– 85, DOI: 10.1039/C0NR00583E
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TEMPO-oxidized cellulose nanofibers
Isogai, Akira; Saito, Tsuguyuki; Fukuzumi, Hayaka
Nanoscale (2011), 3 (1), 71-85CODEN: NANOHL; ISSN:2040-3372. (Royal Society of Chemistry)
A review on prepn. methods and fundamental characteristics of TEMPO-oxidized cellulose nanofibers (TOCN) and tensile strengths, thermal stability, and oxygen permeability of TOCN/poly(lactic acid) composite.
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Zhang, R.; Liu, Y. High energy oxidation and organosolv solubilization for high yield isolation of cellulose nanocrystals (CNC) from Eucalyptus hardwood. Sci. Rep. 2018, 8, 16505, DOI: 10.1038/s41598-018-34667-2
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High energy oxidation and organosolv solubilization for high yield isolation of cellulose nanocrystals (CNC) from Eucalyptus hardwood
Zhang Renli; Liu Yun
Scientific reports (2018), 8 (1), 16505 ISSN:.
Cellulose nanocrystals (CNC) have been widely used as responsive materials, chiral templates, and tough nano-composites due to its unparalleled properties. Acid and enzyme hydrolyses are extensively employed to prepare CNC. These traditional approaches exhibit inherent limitations of corrosion hazards, time-consuming process, and/or low yield. Herein, irradiation oxidation and organosolv solubilization are conducted to cause rapid degradation with simultaneous crystallization of cellulose to achieve approx. 87% yield of CNC. The morphology, spectroscopic, and stability properties of the as-prepared CNC are characterized through UV-vis spectroscopy, zetal potential, XRD, TEM, DLS, GPC, FT-IR and TGA techniques. The resultant CNC suspension presents unique property with high stability after 9 months storage at 4 °C. Moreover, CNC liquid crystal phase is successfully generated by addition of anions or cations solution to the CNC aqueous dispersion without stirring. The innovative approach in this work opens an avenue to obtain CNC directly from lignocellulosic biomass through irradiation oxidation and organosolv solubilization without acid hydrolysis and washing procedure.
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Oksman, K.; Etang, J. A.; Mathew, A. P.; Jonobi, M. Cellulose nanowhiskers separated from a bio-residue from wood bioethanol production. Biomass Bioenergy 2011, 35, 146– 152, DOI: 10.1016/j.biombioe.2010.08.021
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Cellulose nanowhiskers separated from a bioresidue from wood bioethanol production
Oksman, Kristiina; Etang, Jackson A.; Mathew, Aji P.; Jonoobi, Mehdi
Biomass and Bioenergy (2011), 35 (1), 146-152CODEN: BMSBEO; ISSN:0961-9534. (Elsevier Ltd.)
The aim of this study was to explore the utilization of industrial bioresidues as a source of raw material for the industrial prodn. of cellulose nanowhiskers. The used residue, obtained from a bioethanol pilot plant, was first purified using chem. extn. and bleaching, and then sepd. to nanowhiskers by mech. treatments such as ultrasonication, high-pressure homogenization as well as chem. acid hydrolysis. The chem. compns. and characteristics of the bioresidue were studied before and after the purifn. using a TAPPI std., Fourier-transform IR spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric anal. (TGA). The morphol. of the isolated nanowhiskers was characterized using at. force microscope (AFM). The chem. compn. of the used bioresidue was found to be 49.5% cellulose, 42.1% lignin, and 8.4% extractives. The crystallinity of the bioresidue was 14.5% and it increased to more than 73% after the purifn. process. The nanowhiskers isolated using ultrasonication or high-pressure homogenization had better thermal stability than nanowhiskers isolated with acid hydrolysis. The AFM study showed that a simple ultrasonication and homogenization processes resulted in nanosize whiskers with diams. in the 10-20 nm range.
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Herrera, M. A.; Mathew, A. P.; Oksman, K. Characterization of cellulose nanowhiskers: A comparison of two industrial bioresidues. Iop Conf. Ser.: Mater. Sci. Eng. 2012, 31, 012006 DOI: 10.1088/1757-899X/31/1/012006
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Characterization of cellulose nanowhiskers: a comparison of two industrial bio-residues
Herrera, M. A.; Mathew, A. P.; Oksman, K.
IOP Conference Series: Materials Science and Engineering (2012), 31 (), 012006/1-012006/8CODEN: ICSMGW; ISSN:1757-899X. (Institute of Physics Publishing)
Cellulose nanowhiskers sepd. from two different industrial residues, sludge from cellulose prodn. (CNWSL) and lignin residue from ethanol prodn. (CNWER), were compared in order to evaluate their characteristics and their potential as a source for the prodn. of cellulose nanowhiskers (CNWs). It was found that CNWSL and CNWER suspensions exhibited flow birefringence when they were studied through cross-polarized filters. Transmission electron microscopy (TEM) study showed that the CNWSL were longer (377 nm) than CNWER (301 nm). It was also demonstrated that most CNWSL had nanowhiskers between 375-449 nm and CNWER between 300-374 nm. The UV/Vis spectroscopy showed a stronger interference in the UV and visible region for the CNWSL films. The crystallinity, obtained by X-ray anal., was higher for CNWSL (86%) than for CNWER(78%). Finally, the thermal stability appeared to be slightly higher for the CNWER than for CNWSL. Both studied residues seem to be suitable sources for large-scale prodn. of CNWs.
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Roman, M.; Winter, W. T. Effect of sulfate groups from sulfuric acid hydrolysis on the thermal degradation behavior of bacterial cellulose. Biomacromolecules 2004, 5, 1671– 1677, DOI: 10.1021/bm034519+
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Effect of Sulfate Groups from Sulfuric Acid Hydrolysis on the Thermal Degradation Behavior of Bacterial Cellulose
Roman, Maren; Winter, William T.
Biomacromolecules (2004), 5 (5), 1671-1677CODEN: BOMAF6; ISSN:1525-7797. (American Chemical Society)
When used as fillers in polymer composites, the thermostability of cellulose crystals is important. Sulfate groups, introduced during hydrolysis with sulfuric acid, are suspected to diminish the thermostability. To elucidate the relationship between the hydrolysis conditions, the no. of sulfate groups introduced, and the thermal degrdn. behavior of cellulose crystals, bacterial cellulose was hydrolyzed with sulfuric acid under different hydrolysis conditions. The no. of sulfate groups in the crystals was detd. by potentiometric titrn. The thermal degrdn. behavior was investigated by thermogravimetric anal. The sulfate group content increased with acid concn., acid-to-cellulose ratio, and hydrolysis time. Even at low levels, the sulfate groups caused a significant decrease in degrdn. temps. and an increase in char fraction confirming that the sulfate groups act as flame retardants. Profile anal. of the deriv. thermogravimetric curves indicated thermal sepn. of the degrdn. reactions by the sulfate groups into low- and high-temp. processes. The Broido method was used to det. activation energies for the degrdn. processes. The activation energies were lower at larger amts. of sulfate groups suggesting a catalytic effect on the degrdn. reactions. For high thermostability in the crystals, low acid concns., small acid-to-cellulose ratios, and short hydrolysis times should be used.
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Rosa, M. F.; Medeiros, E. S.; Malmonge, J. A.; Gregorski, K. S.; Wood, D. F.; Mattoso, L. H. C.; Glenn, G.; Orts, W. J.; Imam, S. H. Cellulose nanowhiskers from coconut husk fibers: Effect of preparation conditions on their thermal and morphological behavior. Carbohydr. Polym. 2010, 81, 83– 92, DOI: 10.1016/j.carbpol.2010.01.059
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Cellulose nanowhiskers from coconut husk fibers: Effect of preparation conditions on their thermal and morphological behavior
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Carbohydrate Polymers (2010), 81 (1), 83-92CODEN: CAPOD8; ISSN:0144-8617. (Elsevier Ltd.)
Cellulose nanowhiskers were prepd. by sulfuric acid hydrolysis from coconut husk fibers which had previously been submitted to a delignification process. The effects of prepn. conditions on the thermal and morphol. behavior of the nanocrystals were investigated. Cellulose nanowhisker suspensions were characterized by Fourier transform IR spectroscopy (FTIR), transmission electron microscopy (TEM), thermogravimetric anal. (TGA) and X-ray diffraction. Results showed that it was possible to obtain ultrathin cellulose nanowhiskers with diams. as low as 5 nm and aspect ratio of up to 60. A possible correlation between prepn. conditions and particle size was not obsd. Higher residual lignin content was found to increase thermal stability indicating that by controlling reaction conditions one can tailor the thermal properties of the nanowhiskers.
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Surface and Interface Analysis (2009), 41 (6), 453-462CODEN: SIANDQ; ISSN:0142-2421. (John Wiley & Sons Ltd.)
A series of saccharides, including several monohydrates and one amorphous phase, has been investigated by XPS, providing the first database of survey and high-resoln. spectra for this class of compds. Known stoichiometries and XPS-detd. elemental compns. agree well. XPS has sufficient precision for distinguishing the stoichiometries of mono-, di-, and polysaccharides. The C 1s chem. shifts of the acetal and alc. groups are similar for all samples, albeit with slight binding energy increases in the series from monosaccharides to disaccharides and polysaccharides. Increasing X-ray exposure causes a radiation-induced increase of the aliph. hydrocarbon emission at 285 eV, concomitant with the appearance of a high binding energy C 1s emission peak at 289.1 eV and a decrease in the O 1s/C 1s emission intensity ratio. Formation of aliph. hydrocarbon groups is proposed to arise from dehydroxylation, while the increase in the 289.1 eV peak can be attributed to double dehydroxylation at the C1 position or partial oxidn. of an alc. or acetal group. The rate of radiation damage correlates with previously reported rates of thermally induced caramelization.
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Process scale up and characterization of wood cellulose nanocrystals hydrolysed using bioethanol pilot plant
Mathew, Aji P.; Oksman, Kristiina; Karim, Zoheb; Liu, Peng; Khan, Saad Ahmed; Naseri, Narges
Industrial Crops and Products (2014), 58 (), 212-219CODEN: ICRDEW; ISSN:0926-6690. (Elsevier B.V.)
The paper discusses the isolation of cellulose nanocrystals (CNCBE) from wood resources by integrating the processing with pilot-scale bioethanol processing unit. The nanocrystals were isolated from cellulose obtained by acid pretreatment of in a bioethanol pilot-scale facility, followed by a series of chem. processes and subsequent homogenization using a lab-scale homogenizer. The isolated nanocrystals had diams. of 5-15 nm, cellulose I cryst. structure and formed a thick semi-transparent gel at low concn. (2 wt%). XPS data showed that these nanocrystals had predominantly O=C-O surface groups which also contributed to its high neg. zeta potential. Casted CNCBE films showed excellent mech. performance (200 MPa of strength, 16 GPa of modulus) and transparency and were also found to be cytocompatible. The developed process route resulted in high-quality nanocellulose crystals with a yield of 600 g/day.
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Missoum, K.; Sadocco, P.; Causio, J.; Belgacem, M. N.; Bras, J. Antibacterial activity and biodegradability assessment of chemically grafted nanofibrillated cellulose. Mater. Sci. Eng. C Mater. Biol. Appl. 2014, 45, 477– 483, DOI: 10.1016/j.msec.2014.09.037
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Antibacterial activity and biodegradability assessment of chemically grafted nanofibrillated cellulose
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Materials Science & Engineering, C: Materials for Biological Applications (2014), 45 (), 477-483CODEN: MSCEEE; ISSN:0928-4931. (Elsevier B.V.)
Nanofibrillated cellulose (NFC) and their derivs. were prepd. using three chem. surface modification strategies. All grafting was characterized by FTIR and contact angle measurements in order to evaluate the efficiency of grafting. Antibacterial activities of neat and grafted samples were investigated against two kinds of bacteria (i.e. Gram + (Staphylococcus aureus) and Gram - (Klebsiella pneumoniae)). All the grafted samples displayed promising results with at least bacteriostatic effect or bactericidal properties. They also strongly enhanced the photo-catalytic antimicrobial effect of TiO2. This study proves that it is better to use grafted NFC either alone or for functionalization with TiO2 if anti-bacterial properties are desired. The cellulose backbone is known to be easily biodegradable in different biodegrdn. conditions and environments. The chem. surface modifications applied on NFC in the present work did not neg. influence this valuable property of cellulose but help for monitoring this property, which could be very useful for paper, packaging and composites.
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Tavakolian, Mandana; Okshevsky, Mira; van de Ven, Theo G. M.; Tufenkji, Nathalie
ACS Applied Materials & Interfaces (2018), 10 (40), 33827-33838CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
We used hairy nanocryst. cellulose functionalized with aldehyde groups, otherwise known as sterically stabilized nanocryst. cellulose (SNCC), to facilitate the attachment of the antibacterial agents lysozyme and nisin. Immobilization was achieved using a simple, green process that does not require any linker or activator. XPS and Fourier transform IR spectroscopy analyses showed successful attachment of both nisin and lysozyme onto the SNCC. The efficacy of the conjugated nanocellulose against the model bacteria Bacillus subtilis and Staphylococcus aureus was tested in terms of bacterial growth, cell viability, and biofilm formation/removal. The results show that the min. inhibitory concn. of the conjugated nanocellulose is higher than that of lysozyme and nisin in free form, which was expected given that immobilization reduces the possible spatial orientations of these proteins. We obsd. that free nisin is not active against S. aureus after 24 h of exposure due to either deactivation of free nisin or development of resistance in S. aureus against free nisin. Interestingly, we did not observe this phenomenon when the bacteria were exposed to antibacterials immobilized on nanocellulose, suggesting that immobilization of antibacterial agents onto SNCC effectively retains their activity over long time periods. We suggest that antibacterial SNCC is a promising candidate for the development of antibacterial wound dressings.
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Antimicrobial effect of oxidized cellulose salts
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Journal of Industrial Microbiology & Biotechnology (2008), 35 (11), 1247-1252CODEN: JIMBFL; ISSN:1367-5435. (Springer)
Antimicrobial properties of oxidized cellulose and its salts in linters (-L) and microsphere (-M) form (OKCEL H-L, OKCEL Zn-M, OKCEL ZnNa-L, OKCEL ZnNa-M and OKCEL Ag-L) were tested by a diln. method against a spectrum of microbial strains: Escherichia coli, Pseudomonas aeruginosa, Staphylococcus epidermidis, Bacillus licheniformis, Aspergillus niger, Penicillium chrysogenum, Rhizopus oryzae, Scopulariopsis brevicaulis, Candida albicans and Candida tropicalis. OKCEL Ag-L exhibited antimicrobial activity in the range 0.1-3.5% w/v against all the bacteria and fungi involved in this study. Strong inhibition by OKCEL ZnNa-M was obsd. for Staphylococcus epidermidis, Bacillus licheniformis, Rhizopus oryzae, Candida albicans and Candida tropicalis in the range 0.5-2.0% w/v. Antimicrobial effects of oxidized cellulose and its salts in textile form were investigated by a diffusion and diln. method against the spectrum of above-cited microbial strains extended by Clostridium perfringens. Generally, OKCEL Ag-T, OKCEL Zn-T and OKCEL H-T showed high antimicrobial activity against populations of Pseudomonas aeruginosa, Bacillus licheniformis and Staphylococcus epidermidis. OKCEL Zn-T was the only sample suppressing the growth of species.
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Saini, S.; Falco, Ç. Y.; Belgacem, M. N.; Bras, J. Surface cationized cellulose nanofibrils for the production of contact active antimicrobial surfaces. Carbohydr. Polym. 2016, 135, 239– 247, DOI: 10.1016/j.carbpol.2015.09.002
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Saini, Seema; Yucel Falco, Cigdem; Belgacem, Mohamed Naceur; Bras, Julien
Carbohydrate Polymers (2016), 135 (), 239-247CODEN: CAPOD8; ISSN:0144-8617. (Elsevier Ltd.)
In the last decade, a new fiber pretreatment has been proposed to make easy cellulose fibrillation into microfibrils. In this context, different surface cationized MFC was prepd. by optimizing the exptl. parameters for cellulose fibers pretreatment before fibrillation. All MFCs were characterized by conductometric titrn. to establish degree of substitution, field emission gun SEM (FEG-SEM), at. force microscopy (AFM) and optical microscopy assessed the effect of pretreatment on the morphol. of the ensuing MFCs. Antibacterial activities of neat and cationized MFC samples were investigated against Gram pos. bacteria (Bacillus subtilis, Staphylococcus aureus) and Gram neg. bacteria (Escherichia coli). The CATMFC sample at DS greater than 0.18 displayed promising results with antibacterial properties without any leaching of quaternary ammonium into the environment. This work proved the potential of cationic MFCs with specific DS for contact active antimicrobial surface applications in active food packaging, medical packaging or in health and cosmetic field.
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Breijyeh, Zeinab; Jubeh, Buthaina; Karaman, Rafik
Molecules (2020), 25 (6), 1340CODEN: MOLEFW; ISSN:1420-3049. (MDPI AG)
Antimicrobial resistance represents an enormous global health crisis and one of the most serious threats humans face today. Some bacterial strains have acquired resistance to nearly all antibiotics. Therefore, new antibacterial agents are crucially needed to overcome resistant bacteria. In 2017, the World Health Organization (WHO) has published a list of antibiotic-resistant priority pathogens, pathogens which present a great threat to humans and to which new antibiotics are urgently needed the list is categorized according to the urgency of need for new antibiotics as crit., high, and medium priority, in order to guide and promote research and development of new antibiotics. The majority of the WHO list is Gram-neg. bacterial pathogens. Due to their distinctive structure, Gram-neg. bacteria are more resistant than Gram-pos. bacteria, and cause significant morbidity and mortality worldwide. Several strategies have been reported to fight and control resistant Gram-neg. bacteria, like the development of antimicrobial auxiliary agents, structural modification of existing antibiotics, and research into and the study of chem. structures with new mechanisms of action and novel targets that resistant bacteria are sensitive to. Research efforts have been made to meet the urgent need for new treatments; some have succeeded to yield activity against resistant Gram-neg. bacteria by deactivating the mechanism of resistance, like the action of the β-lactamase Inhibitor antibiotic adjuvants. Another promising trend was by referring to nature to develop naturally derived agents with antibacterial activity on novel targets, agents such as bacteriophages, DCAP(2-((3-(3,6-dichloro-9H-carbazol-9-yl)-2-hydroxypropyl)amino)-2(hydroxymethyl)propane1,3- diol, Odilorhabdins (ODLs), peptidic benzimidazoles, quorum sensing (QS) inhibitors, and metal-based antibacterial agents.
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Herbaud, Marie-Laure; Guiseppi, Annick; Denizot, Francois; Haiech, Jacques; Kilhoffer, Marie-Claude
Biochimica et Biophysica Acta, Molecular Cell Research (1998), 1448 (2), 212-226CODEN: BBAMCO; ISSN:0167-4889. (Elsevier B.V.)
Few systematic studies have been devoted to investigating the role of Ca2+ as an intracellular messenger in prokaryotes. Here we report an investigation on the potential involvement of Ca2+ in signalling in Bacillus subtilis, a Gram-pos. bacterium. Using aequorin, it is shown that B. subtilis cells tightly regulate intracellular Ca2+ levels. This homeostasis can be changed by an external stimulus such as hydrogen peroxide, pointing to a relationship between oxidative stress and Ca2+ signalling. Also, B. subtilis growth appears to be intimately linked to the presence of Ca2+, as normal growth can be immediately restored by adding Ca2+ to an almost non-growing culture in EGTA contg. Luria broth medium. Addn. of Fe2+ or Mn2+ also restores growth, but with 5-6 h delay, whereas Mg2+ did not have any effect. In addn., the expression of alkyl hydroperoxide reductase C (AhpC), which is strongly enhanced in bacteria grown in the presence of EGTA, also appears to be regulated by Ca2+. Finally, using 45Ca2+ overlay on membrane electrotransferred two-dimensional gels of B. subtilis, four putative Ca2+ binding proteins were found, including AhpC. Our results provide strong evidence for a regulatory role for Ca2+ in bacterial cells.
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Growth of a wall-less, L-form of Escherichia coli specifically requires calcium, and in its absence, cells ceased dividing, became spherical, swelled, developed large vacuoles, and eventually lysed. The key cell division protein, FtsZ, was present in the L-form at a concn. five times less than that in the parental strain. One interpretation of these results is that the L-form possesses an enzoskeleton partly regulated by calcium.
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Valenzuela, S. V.; Valls, C.; Schink, V.; Sánchez, D.; Blanca Roncero, M.; Diaz, P.; Martinez, J.; Javier Pastor, F. I. Differential activity of lytic polysaccharide monooxygenases on celluloses of different crystallinity. Effectiveness in the sustainable production of cellulose nanofibrils. Carbohydr. Polym. 2019, 207, 59– 67, DOI: 10.1016/j.carbpol.2018.11.076
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Differential activity of lytic polysaccharide monooxygenases on celluloses of different crystallinity. Effectiveness in the sustainable production of cellulose nanofibrils
Valenzuela, Susana V.; Valls, Cristina; Schink, Viviane; Sanchez, Daniel; Roncero, M. Blanca; Diaz, Pilar; Martinez, Josefina; Pastor, F. I. Javier
Carbohydrate Polymers (2019), 207 (), 59-67CODEN: CAPOD8; ISSN:0144-8617. (Elsevier Ltd.)
A series of cellulosic substrates has been produced, treated with lytic polysaccharide monooxygenase (LPMO) from Streptomyces ambofaciens (SamLPMO10C), and analyzed by high performance anion exchange chromatog. (HPAEC) with pulsed amperometric detection (PAD). The activity of the bacterial LPMO showed high variability depending on the origin and degree of crystallinity of the substrate. Addnl., we tested the effectiveness of SamLPMO10C in the nanofibrillation of flax, a high cryst. agricultural fiber, as a single pretreatment or in combination with cellulases. All pretreatments were followed by a mech. defibrillation by high-pressure homogenization (HPH) to obtain cellulose nanofibrils (NFC). The combined LPMO-cellulase treatment showed higher fibrillation yield, optical transmittance and carboxylate content than control reactions. Therefore, it could be explored as a promising green alternative to reduce the energy consumption in the prodn. of NFC. To our knowledge, this is the first study reporting the effect of a bacterial LPMO in nanocellulose prodn.
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Abstract
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Figure 1
Figure 1. Flow diagram of the experimental process.
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Figure 2
Figure 2. HPAEC chromatograph of soluble products detected after activity of MtLPMO on OS-pretreated tunic. The profile of the products reveals a mixed C1/C4-oxidizing activity. The products of blank reactions in the absence of enzyme (blank reaction 1, without enzyme, only ascorbic acid, and copper equivalent to LPMOs added) and electron donor (blank reaction 2 and only MtLPMO) are also depicted.
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Figure 3
Figure 3. (A) AFM images of TNCs isolated from the untreated material (A), OS-pretreated material (B), OS-pretreated material w/o bleaching (B_w/o), OS/LPMO-pretreated material (C), and OS/LPMO-pretreated material w/o bleaching (C_w/o). (B) TNC diameter measured with Nanoscope V software.
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Figure 4
Figure 4. TGA graphs of the TNCs isolated from tunic biomass after different treatments.
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Figure 5
Figure 5. (A) XPS detailed spectra of the C 1 s region before (solid line) and after (dashed line) the LPMO post-treatment of the untreated material (A), OS-pretreated material (B), and OS/LPMO-pretreated material (C). (B) Stoichiometric amount of the molecular species.
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Figure 6
Figure 6. Growth curve of B. subtilis and E. coli in the presence of 0.25% w/v TNCs: untreated material (A), OS-pretreated material (B), OS/LPMO-pretreated material (C), and OS/LPMO-pretreated material w/o bleaching (C_w/o).
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Figure 7
Figure 7. (A) AFM images of the untreated material (A_post-treated), OS-pretreated material (B_post-treated), OS/LPMO-pretreated material (C_post-treated), and OS/LPMO-pretreated material w/o bleaching (C_{w/o - post-treated}) and (B) TNC diameter measurements after LPMO post-treatment, as identified by the Nanoscope V software.
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References
This article references 75 other publications.
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  Nanocellulose properties and applications in colloids and interfaces
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  In this review we introduce recent advances in the development of cellulose nanomaterials and the construction of high order structures by applying some principles of colloid and interface science. These efforts take advantage of natural assemblies in the form of fibers that nature constructs by a biogenetic bottom-up process that results in hierarchical systems encompassing a wide range of characteristic sizes. Following the reverse process, a top-down deconstruction, cellulose materials can be cleaved from fiber cell walls. The resulting nanocelluloses, mainly cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC, i.e., defect-free, rod-like cryst. residues after acid hydrolysis of fibers), have been the subject of recent interest. This originates from the appealing intrinsic properties of nanocelluloses: nanoscale dimensions, high surface area, morphol., low d., chirality and thermo-mech. performance. Directing their assembly into multiphase structures is a quest that can yield useful outcomes in many revolutionary applications. As such, we discuss the use of non-specific forces to create thin films of nanocellulose at the air-solid interface for applications in nano-coatings, sensors, etc. Assemblies at the liq.-liq. and air-liq. interfaces will be highlighted as means to produce Pickering emulsions, foams and aerogels. Finally, the prospects of a wide range of hybrid materials and other systems that can be manufd. via self and directed assembly will be introduced in light of the unique properties of nanocelluloses.
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  A review. Nanocellulose is often being regarded as the next generation renewable reinforcement for the prodn. of high performance biocomposites. This feature article reviews the various nanocellulose reinforced polymer composites reported in literature and discusses the potential of nanocellulose as reinforcement for the prodn. of renewable high performance polymer nanocomposites. The theor. and exptl. detd. tensile properties of nanocellulose are also reviewed. In addn. to this, the reinforcing ability of BC and NFC is juxtaposed. In order to analyze the various cellulose-reinforced polymer nanocomposites reported in literature, Cox-Krenchel and rule-of-mixt. models have been used to elucidate the potential of nanocellulose in composite applications. There may be potential for improvement since the tensile modulus and strength of most cellulose nanocomposites reported in literature scale linearly with the tensile modulus and strength of the cellulose nanopaper structures. Better dispersion of individual cellulose nanofibers in the polymer matrix may improve composite properties.
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  Klemm, Dieter; Kramer, Friederike; Moritz, Sebastian; Lindstroem, Tom; Ankerfors, Mikael; Gray, Derek; Dorris, Annie
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  A review. Cellulose fibrils with widths in the nanometer range are nature-based materials with unique and potentially useful features. Most importantly, these novel nanocelluloses open up the strongly expanding fields of sustainable materials and nanocomposites, as well as medical and life-science devices, to the natural polymer cellulose. The nanodimensions of the structural elements result in a high surface area and hence the powerful interaction of these celluloses with surrounding species. This Review assembles the current knowledge on the isolation of microfibrillated cellulose from wood and its application in nanocomposites; the prepn. of nanocryst. cellulose and its use as a reinforcing agent; and the biofabrication of bacterial nanocellulose, as well as its evaluation as a biomaterial for medical implants.
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  A review discussing chem. and phys. features of the most dominant fundamental building block in the biosphere, cellulose nanocrystals. A brief introduction to cellulose was followed by the discussion of morphol., chem., including prepn. and chem. routes for functionalization, and self-assembly in various media under various conditions, and applications in the nanocomposites.
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  Cellulose nanocrystals and related nanocomposites: Review of some properties and challenges
  Mariano, Marcos; El Kissi, Nadia; Dufresne, Alain
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  A review. Cellulosic nanoparticles with high Young's modulus, crystallinity, sp. surface area, and aspect ratio can be found in the natural structure of plant fibers. Indeed, lignocellulosic fibers consist of semicryst. cellulose nanofibrils embedded in an amorphous matrix mainly composed of lignin and hemicelluloses. These nanostructures give the mech. strength to higher plant cells, and are biodegradable, renewable, resistant, and widely available to produce nanocomposites with low d., and improved and controlled mech., optical, and barrier properties. Nanoparticles can be extd. from cellulose using a top-down mech. or chem. assisted deconstructing strategy, and owing to their highly reactive surface ensuing nanomaterials can be chem. modified to tailor their properties for a wide range of applications. This review is limited to cellulose chem. extd. nanocrystals and aims to provide an overview about several aspects that involve this material, including sources, properties, challenges, and perspectives. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014.
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  Jonoobi, M.; Oladi, R.; Davoudpour, Y.; Oksman, K.; Dufrense, A.; Hamzeh, Y.; Davoodi, R. Different preparation methods and properties of nanostructured cellulose from various natural resources and residues: a review. Cellulose 2015, 22, 935– 969, DOI: 10.1007/s10570-015-0551-0
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  Different preparation methods and properties of nanostructured cellulose from various natural resources and residues: a review
  Jonoobi, Mehdi; Oladi, Reza; Davoudpour, Yalda; Oksman, Kristiina; Dufresne, Alain; Hamzeh, Yahya; Davoodi, Reza
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  A review. The main goal of this article is to provide an overview of recent research in the area of cellulose nanomaterial prodn. from different sources. Due to their abundance, renewability, high strength and stiffness, eco-friendliness and low wt., numerous studies have been reported on the isolation of cellulose nanomaterials from different cellulosic sources and their use in high-performance applications. This report covers an introduction to the definition of nanocellulose as well as the methods used for isolation of nanomaterials (including nanocrystals and nanofibers, CNCs and CNFs, resp.) from various sources. The web-like network structure (CNFs) can be extd. from natural sources using mech. processes, which include high-pressure homogenization, grinding and refining treatments. Also, rod-like CNCs can be isolated from sources such as wood, plant fibers, agricultural and industrial bioresidues, tunicates and bacterial cellulose using an acid hydrolysis process. Following this, the article focuses on the characterization methods, material properties and structures. Encyclopedic characteristics of CNFs and CNCs obtained from different source materials and/or studies are also included. The current report is a comprehensive review of the literature regarding nanocellulose isolation and demonstrates the potential of cellulose nanomaterials for a wide range of high-tech applications.
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  Börjesson, M.; Westman, G. Crystalline Nanocellulose — Preparation, Modification, and Properties, Cellulose-Fundamental Aspects and Current Trends, Matheus Poletto and Heitor Luiz Ornaghi Junior, IntechOpen, December 9th 2015. DOI: 10.5772/61899 . Available from: https://www.intechopen.com/books/cellulose-fundamental-aspects-and-current-trends/crystalline-nanocellulose-preparation-modification-and-properties
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  Zhao, Y.; Li, J. Excellent chemical and material cellulose from tunicates: diversity in cellulose production yield and chemical and morphological structures from different tunicate species. Cellulose 2014, 21, 3427– 3441, DOI: 10.1007/s10570-014-0348-6
  10
  Excellent chemical and material cellulose from tunicates: diversity in cellulose production yield and chemical and morphological structures from different tunicate species
  Zhao, Yadong; Li, Jiebing
  Cellulose (Dordrecht, Netherlands) (2014), 21 (5), 3427-3441CODEN: CELLE8; ISSN:0969-0239. (Springer)
  The high crystallinity and the high microfibrils aspect ratio of tunicate cellulose (TC) indicate TC's excellent chem. and material applications. However, its quantity and quality from different species have never been systematically reported and compared. In this study, the tunics of Ciona intestinalis (CI), Ascidia sp. (AS), Halocynthia roretzi (HR) and Styela plicata (SP) were processed to TC after an identical prehydrolysis-kraft cooking-bleaching sequence, while the tunicate fibrils were chem. and structurally characterized in situ and during the sequence. All tunics studied were composed of cryst. cellulose embedded with protein, lipids, sulfated glycans and mucopolysaccharides. The native composite structures are all very compact. However, the tunics from Phlebobranchia order (CI and AS) are soft, while those from Stolidobranchia, HR and SP, are hard. Fibrous cellulose could be prepd. after removing the lipids, sulfated glycans and mucopolysaccharides through prehydrolysis, protein removal through kraft cooking and a final purifn. by bleaching. The final product is ∼100% pure cellulose which is in large mol. masses, composed of highly cryst. Iβ crystals, in elementary microfibrils form, with high sp. surface area and thermal stability. There were lower TC yields from the soft tunics than from the hard ones. The cellulose fibrils had a section shape of lozenges with higher crystallinity. This study demonstrates that TC could be obtained in different yields and exhibited different chem. and morphol. structures depending on the species. There is a great potential of tunicate resources for prepg. excellent chem. and material cellulose.
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11. 11
  Mathew, A. P.; Dufresne, A. Morphological investigation of nanocomposites from sorbitol plasticized starch and tunicin whiskers. Biomacromolecules 2002, 3, 609– 617, DOI: 10.1021/bm0101769
  11
  Morphological investigation of nanocomposites from sorbitol plasticized starch and tunicin whiskers
  Mathew, Aji P.; Dufresne, Alain
  Biomacromolecules (2002), 3 (3), 609-617CODEN: BOMAF6; ISSN:1525-7797. (American Chemical Society)
  Nanocomposites were prepd. from waxy maize starch (I) plasticized with sorbitol as the matrix and a stable aq. suspension of tunicin (II) whiskers -- an animal cellulose -- as the reinforcing phase. The composites were conditioned at different relative humidity levels. The conditioned films were characterized using SEM, DSC, water uptake expts., and WAXS studies. Contrarily to a previous report concerning II whisker-filled glycerol plasticized I nanocomposites (Macromols. 2000, 33, 8344), the present system exhibited a single glass-rubber transition, and no evidence of transcrystn. of amylopectin (III) on II whisker surfaces and resultant anti-plasticizing effects were obsd. It was shown that the glass-rubber transition temp. of the plasticized III matrix 1st increases up to a whiskers content around 10-15 wt.%, and then decreases. A significant increase in crystallinity was obsd. in the composites by increasing either moisture content or whiskers content.
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12. 12
  Zhao, Y.; Moser, C.; Lindström, M. E.; Henriksson, G.; Li, J. Cellulose nanofibers from softwood, hardwood, and tunicate: preparation–structure–film performance interrelation. Appl. Mater. Interfaces 2017, 9, 13508– 13519, DOI: 10.1021/acsami.7b01738
  12
  Cellulose Nanofibers from Softwood, Hardwood, and Tunicate: Preparation-Structure-Film Performance Interrelation
  Zhao, Yadong; Moser, Carl; Lindstroem, Mikael E.; Henriksson, Gunnar; Li, Jiebing
  ACS Applied Materials & Interfaces (2017), 9 (15), 13508-13519CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
  This work reveals the structural variations of cellulose nanofibers (CNF) prepd. from different cellulose sources, softwood (Picea abies), hardwood (E. grandis x E. urophylla) and tunicate (Ciona intestinalis), using different prepn. processes, and their correlations to the formation and performance of the films prepd. from the CNF. Here the CNF are prepd. from wood chem. pulps and tunicate isolated cellulose by an identical homogenization treatment subsequent to either an enzymic hydrolysis or a 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-mediated oxidn. They show a large structural diversity in terms of chem., morphol., and cryst. structure. Among others, the tunicate CNF consist of purer cellulose and have higher d.p. than wood CNF. Introduction of surface charges via the TEMPO-mediated oxidn. is found to have significant impacts on the structure, morphol., optical, mech., thermal, and hydrophobic properties of the prepd. films. For example, the film d. is closely related to the charge d. of the used CNF and the tensile stress of the films is correlated to the crystallinity index of the CNF. In turn the CNF structure is detd. by the cellulose sources and the prepn. processes. This study provides useful information and knowledge for understanding the importance of the raw material for the quality of CNF for various types of application.
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13. 13
  Sacui, I. A.; Nieuwendaal, R. C.; Burnett, D. J.; Stranick, S. J.; Jorfi, M.; Weder, C.; Foster, E. J.; Olsson, R. T.; Gilman, J. W. Comparison of the properties of cellulose nanocrystals and cellulose nanofibrils isolated from bacteria, tunicate, and wood processed using acid, enzymatic, mechanical, and oxidative methods. ACS Appl. Mater. Interfaces 2014, 6, 6127– 6138, DOI: 10.1021/am500359f
  13
  Comparison of the Properties of Cellulose Nanocrystals and Cellulose Nanofibrils Isolated from Bacteria, Tunicate, and Wood Processed Using Acid, Enzymatic, Mechanical, and Oxidative Methods
  Sacui, Iulia A.; Nieuwendaal, Ryan C.; Burnett, Daniel J.; Stranick, Stephan J.; Jorfi, Mehdi; Weder, Christoph; Foster, E. Johan; Olsson, Richard T.; Gilman, Jeffery W.
  ACS Applied Materials & Interfaces (2014), 6 (9), 6127-6138CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
  This work describes the measurement and comparison of several important properties of native cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs), such as crystallinity, morphol., aspect ratio, and surface chem. Measurement of the fundamental properties of seven different CNCs/CNFs, from raw material sources (bacterial, tunicate, and wood) using typical hydrolysis conditions (acid, enzymic, mech., and 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-mediated oxidn.), was accomplished using a variety of measurement methods. Atomic force microscopy (AFM), TEM, and 13C cross-polarization magic angle spinning (CPMAS) NMR spectroscopy were used to conclude that CNCs, which are rodlike in appearance, have a higher crystallinity than CNFs, which are fibrillar in appearance. CNC aspect ratio distributions were measured and ranged from 148±147 for tunicate-CNCs to 23±12 for wood-CNCs. Hydrophobic interactions, measured using inverse gas chromatog. (IGC), were found to be an important contribution to the total surface energy of both types of cellulose. In all cases, a trace amt. of naturally occurring fluorescent compds. was obsd. after hydrolysis. Confocal and Raman microscopy were used to confirm that the fluorescent species were unique for each cellulose source, and demonstrated that such methods can be useful for monitoring purity during CNC/CNF processing. This study reveals the broad, tunable, multi-dimensional material space in which CNCs and CNFs exist.
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14. 14
  Elazzouzi-Hafraoui, S.; Nishiyama, Y.; Putaux, J.-L.; Heux, L.; Dubreuil, F.; Rochas, C. The shape and size distribution of crystalline nanoparticles prepared by acid hydrolysis of native cellulose. Biomacromolecules 2008, 9, 57– 65, DOI: 10.1021/bm700769p
  14
  The Shape and Size Distribution of Crystalline Nanoparticles Prepared by Acid Hydrolysis of Native Cellulose
  Elazzouzi-Hafraoui, Samira; Nishiyama, Yoshiharu; Putaux, Jean-Luc; Heux, Laurent; Dubreuil, Frederic; Rochas, Cyrille
  Biomacromolecules (2008), 9 (1), 57-65CODEN: BOMAF6; ISSN:1525-7797. (American Chemical Society)
  The shape and size distribution of cryst. nanoparticles resulting from the sulfuric acid hydrolysis of cellulose from cotton, Avicel, and tunicate were investigated using transmission electron microscopy (TEM) and at. force microscopy (AFM) as well as small- and wide-angle X-ray scattering (SAXS and WAXS). Images of neg. stained and cryo-TEM specimens showed that the majority of cellulose particles were flat objects constituted by elementary crystallites whose lateral adhesion was resistant against hydrolysis and sonication treatments. Moreover, tunicin whiskers were described as twisted ribbons with an estd. pitch of 2.4-3.2 μm. Length and width distributions of all samples were generally well described by log-normal functions, with the exception of tunicin, which had less lateral aggregation. AFM observation confirmed that the thickness of the nanocrystals was almost const. for a given origin and corresponded to the crystallite size measured from peak broadening in WAXS spectra. Exptl. SAXS profiles were numerically simulated, combining the dimensions and size distribution functions detd. by the various techniques.
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15. 15
  Mathew, A. P.; Thielemans, W.; Dufresne, A. Mechanical properties of nanocomposites from sorbitol plasticized starch and tunicin whiskers. J. Appl. Polym. Sci. 2008, 109, 4065– 4074, DOI: 10.1002/app.28623
  15
  Mechanical properties of nanocomposites from sorbitol plasticized starch and tunicin whiskers
  Mathew, Aji P.; Thielemans, W.; Dufresne, Alain
  Journal of Applied Polymer Science (2008), 109 (6), 4065-4074CODEN: JAPNAB; ISSN:0021-8995. (John Wiley & Sons, Inc.)
  Nanocomposite materials were obtained using sorbitol plasticized waxy maize starch as matrix and tunicin whiskers as the reinforcement. The effect of filler load (0-25 wt. % whiskers) and the relative humidity levels (0-98%) on the mech. behavior of the films are discussed for linear and nonlinear deformation. The performance of the films is explained, based on the morphol. and structural behavior of the composite materials (Mathew and Dufresne, Biomacromols. 2002, 3, 609). The nanocomposites exhibit good mech. strength due to the strong interaction between tunicin whiskers, matrix, plasticizer (sorbitol), and water, and due to the ability of the cellulose filler to form a rigid three-dimensional network. The evolution of Tg as a function of relative humidity level and filler load is studied in detail. A decrease in crystallinity of the amylopectin phase is obsd. at high filler loads, due to the resistance to chain rearrangement imposed by the whiskers. The mech. strength increased proportionally with filler loads, showing an effective stress transfer from the matrix to the whiskers. An even distribution of whiskers (as detd. by SEM) and plasticizer in the matrix contributes to the mech. performance. The mech. properties of the nanocomposites showed a strong dependence on relative humidity conditions.
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16. 16
  Squinca, P.; Bilatto, S.; Badino, A. C.; Farinas, C. S. Nanocellulose production in future biorefineries: an integrated approach using tailor-made enzymes. ACS Sustainable Chem. Eng. 2020, 8, 2277– 2286, DOI: 10.1021/acssuschemeng.9b06790
  16
  Nanocellulose Production in Future Biorefineries: An Integrated Approach Using Tailor-Made Enzymes
  Squinca, Paula; Bilatto, Stanley; Badino, Alberto C.; Farinas, Cristiane S.
  ACS Sustainable Chemistry & Engineering (2020), 8 (5), 2277-2286CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)
  The development of process engineering approaches to integrate the prodn. of biofuels and high value-added biobased products, such as enzymes and nanocellulose, is crucial to improve the financial performance and sustainability of lignocellulosic biomass biorefineries. Here, the feasibility of applying enzymes produced on-site to obtain nanocellulose was evaluated using eucalyptus cellulose pulp as a model feedstock. A systematic anal. of the structural properties of the nanomaterials obtained after hydrolysis using a cellulolytic enzymic complex with high endoglucanase specific activity (17.09 IU/mgprotein), produced by Aspergillus niger, followed by sonication, revealed that longer ball milling pretreatment and reaction times favored extn. of the cellulose nanocrystals (CNCs). The highest yield (24.6%) of CNCs was achieved using 96 h of enzymic hydrolysis of the ball-milled cellulose pulp, followed by sonication for 5 min. The CNCs presented approx. lengths of 294.0 nm and diams. of 24.0 nm, and the crystallinity index increased from 57.5% to 78.3%, compared to the cellulose pulp that was only ball milled. These findings demonstrated that nanocelluloses could be successfully extd. using on-site produced enzymes and that the sustainable integrated process reported here could contribute to the development of the nascent biobased economy. Cellulose nanocrystals were obtained by enzymic hydrolysis using on-site produced enzymes and eucalyptus cellulose pulp in a sustainable integrated process.
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17. 17
  Henriksson, M.; Henriksson, G.; Berglund, L. A.; Lindström, T. An environmentally friendly method for enzyme-assisted preparation of microfibrillated cellulose (MFC) nanofibers. Eur. Polym. J. 2007, 43, 3434– 3441, DOI: 10.1016/j.eurpolymj.2007.05.038
  17
  An environmentally friendly method for enzyme-assisted preparation of microfibrillated cellulose (MFC) nanofibers
  Henriksson, M.; Henriksson, G.; Berglund, L. A.; Lindstroem, T.
  European Polymer Journal (2007), 43 (8), 3434-3441CODEN: EUPJAG; ISSN:0014-3057. (Elsevier Ltd.)
  Microfibrillated cellulose nanofibers (MFC) provide strong reinforcement in polymer nanocomposites. In the present study, cellulosic wood fiber pulps are treated by endoglucanases or acid hydrolysis in combination with mech. shearing in order to disintegrate MFC from the wood fiber cell wall. After successful disintegration, the MFC nanofibers were studied by at. force microscopy (AFM). Enzyme-treatment was found to facilitate disintegration, and the MFC nanofibers produced also showed higher av. molar mass and larger aspect ratio than nanofibers resulting from acidic pretreatment.
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18. 18
  Hu, J.; Tian, D.; Renneckar, S.; Saddler, J. N. Enzyme-mediated nanofibrillation of cellulose by the synergistic actions of an endoglucanase, lytic polysaccharide monooxygenase (LPMO) and xylanase. Sci. Rep. 2018, 8, 3195, DOI: 10.1038/s41598-018-21016-6
  18
  Enzyme mediated nanofibrillation of cellulose by the synergistic actions of an endoglucanase, lytic polysaccharide monooxygenase (LPMO) and xylanase
  Hu Jinguang; Tian Dong; Saddler Jack N; Tian Dong; Renneckar Scott
  Scientific reports (2018), 8 (1), 3195 ISSN:.
  Physiochemical methods have generally been used to "open-up" biomass substrates/pulps and have been the main method used to fibrillate cellulose. However, recent work has shown that canonical cellulase enzymes such as endoglucanases, in combination with "amorphogenesis inducing" proteins such as lytic polysaccharide monooxygenases (LPMO), swollenin and hemicellulases, are able to increase cellulose accessibility. In the work reported here different combinations of endoglucanase, LPMO and xylanase were applied to Kraft pulps to assess their potential to induce fibrillation at low enzyme loading over a short time period. Although gross fiber properties (fiber length, width and morphology) were relatively unchanged, over a short period of time, the intrinsic physicochemical characteristics of the pulp fibers (e.g. cellulose accessibility/DP/crystallinity/charge) were positively enhanced by the synergistic cooperation of the enzymes. LPMO addition resulted in the oxidative cleavage of the pulps, increasing the negative charge (~100 mmol kg(-1)) on the cellulose fibers. This improved cellulose nanofibrilliation while stabilizing the nanofibril suspension (zeta potential ζ = ~60 mV), without sacrificing nanocellulose thermostability. The combination of endoglucanase, LPMO and xylanases was shown to facilitate nanofibrillation, potentially reducing the need for mechanical refining while resulting in a pulp with a more uniform nanofibril composition.
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19. 19
  Hu, J.; Arantes, V.; Pribowo, A.; Saddler, J. N. The synergistic action of accessory enzymes enhances the hydrolytic potential of a “cellulase mixture” but is highly substrate specific. Biotechnol. Biofuels 2013, 6, 112, DOI: 10.1186/1754-6834-6-112
  19
  The synergistic action of accessory enzymes enhances the hydrolytic potential of a "cellulase mixture" but is highly substrate specific
  Hu, Jinguang; Arantes, Valdeir; Pribowo, Amadeus; Saddler, Jack N.
  Biotechnology for Biofuels (2013), 6 (), 112CODEN: BBIIFL; ISSN:1754-6834. (BioMed Central Ltd.)
  Currently, the amt. of protein/enzyme required to achieve effective cellulose hydrolysis is still too high. One way to reduce the amt. of protein/enzyme required is to formulate a more efficient enzyme cocktail by adding so-called accessory enzymes such as xylanase, lytic polysaccharide monooxygenase (AA9, formerly known as GH61), etc., to the cellulase mixt. Previous work has shown the strong synergism that can occur between cellulase and xylanase mixts. during the hydrolysis of steam pretreated corn stover, requiring lower protein loading to achieve effective hydrolysis. However, relatively high loadings of xylanases were required. When family 10 and 11 endo-xylanases and family 5 xyloglucanase were supplemented to a com. cellulase mixt. varying degrees of improved hydrolysis over a range of pretreated, lignocellulosic substrates were obsd. Results: The potential synergistic interactions between cellulase monocomponents and hemicellulases from family 10 and 11 endo-xylanases (GH10 EX and GH11 EX) and family 5 xyloglucanase (GH5 XG), during hydrolysis of various steam pretreated lignocellulosic substrates, were assessed. It was apparent that the hydrolytic activity of cellulase monocomponents was enhanced by the addn. of accessory enzymes although the "boosting" effect was highly substrate specific. The GH10 EX and GH5 XG both exhibited broad substrate specificity and showed strong synergistic interaction with the cellulases when added individually. The GH10 EX was more effective on steam pretreated agriculture residues and hardwood substrates whereas GH5 XG addn. was more effective on softwood substrates. The synergistic interaction between GH10 EX and GH5 XG when added together further enhanced the hydrolytic activity of the cellulase enzymes over a range of pretreated lignocellulosic substrates. GH10 EX addn. could also stimulate further cellulose hydrolysis when added to the hydrolysis reactions when the rate of hydrolysis had levelled off. Conclusions: Endo-xylanases and xyloglucanases interacted synergistically with cellulases to improve the hydrolysis of a range of pretreated lignocellulosic substrates. However, the extent of improved hydrolysis was highly substrate dependent. It appears that those accessory enzymes, such as GH10 EX and GH5 XG, with broader substrate specificities promoted the greatest improvements in the hydrolytic performance of the cellulase mixt. on all of the pretreated biomass substrates.
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20. 20
  Westereng, B.; Ishida, T.; Vaaje-Kolstad, G.; Wu, M.; Eijsink, V. G.; Igarashi, K.; Samejima, M.; Ståhlberg, J.; Horn, S. J.; Sandgren, M. The putative endoglucanase PcGH61D from Phanerochaete chrysosporium is a metal-dependent oxidative enzyme that cleaves cellulose. PLoS One 2011, 6, e27807 DOI: 10.1371/journal.pone.0027807
  20
  The putative endoglucanase PcGH61D from Phanerochaete chrysosporium is a metal-dependent oxidative enzyme that cleaves cellulose
  Westereng, Bjoerge; Ishida, Takuya; Vaaje-Kolstad, Gustav; Wu, Miao; Eijsink, Vincent G. H.; Igarashi, Kiyohiko; Samejima, Masahiro; Staahlberg, Jerry; Horn, Svein J.; Sandgren, Mats
  PLoS One (2011), 6 (11), e27807CODEN: POLNCL; ISSN:1932-6203. (Public Library of Science)
  Many fungi growing on plant biomass produce proteins currently classified as glycoside hydrolase family 61 (GH61), some of which are known to act synergistically with cellulases. In this study we show that PcGH61D, the gene product of an open reading frame in the genome of Phanerochaete chrysosporium, is an enzyme that cleaves cellulose using a metal-dependent oxidative mechanism that leads to generation of aldonic acids. The activity of this enzyme and its beneficial effect on the efficiency of classical cellulases are stimulated by the presence of electron donors. Expts. with reduced cellulose confirmed the oxidative nature of the reaction catalyzed by PcGH61D and indicated that the enzyme may be capable of penetrating into the substrate. Considering the abundance of GH61-encoding genes in fungi and genes encoding their functional bacterial homologues currently classified as carbohydrate binding modules family 33 (CBM33), this enzyme activity is likely to turn out as a major determinant of microbial biomass-degrading efficiency.
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21. 21
  Harris, P. V.; Welner, D.; McFarland, K. C.; Re, E.; Navarro Poulsen, J. C.; Brown, K.; Salbo, R.; Ding, H.; Vlasenko, E.; Merino, S.; Xu, F.; Cherry, J.; Larsen, S.; Lo Leggio, L. Stimulation of lignocellulosic biomass hydrolysis by proteins of Glycoside Hydrolase Family 61: Structure and function of a large, enigmatic family. Biochemistry 2010, 49, 3305– 3316, DOI: 10.1021/bi100009p
  21
  Stimulation of Lignocellulosic Biomass Hydrolysis by Proteins of Glycoside Hydrolase Family 61: Structure and Function of a Large, Enigmatic Family
  Harris, Paul V.; Welner, Ditte; McFarland, K. C.; Re, Edward; Navarro Poulsen, Jens-Christian; Brown, Kimberly; Salbo, Rune; Ding, Hanshu; Vlasenko, Elena; Merino, Sandy; Xu, Feng; Cherry, Joel; Larsen, Sine; Lo Leggio, Leila
  Biochemistry (2010), 49 (15), 3305-3316CODEN: BICHAW; ISSN:0006-2960. (American Chemical Society)
  Currently, the relatively high cost of enzymes such as glycoside hydrolases that catalyze cellulose hydrolysis represents a barrier to commercialization of a biorefinery capable of producing renewable transportable fuels such as ethanol from abundant lignocellulosic biomass. Among the many families of glycoside hydrolases that catalyze cellulose and hemicellulose hydrolysis, few are more enigmatic than family 61 (GH61), originally classified based on measurement of very weak endo-1,4-β-D-glucanase activity in one family member. Here we show that certain GH61 proteins lack measurable hydrolytic activity by themselves but in the presence of various divalent metal ions can significantly reduce the total protein loading required to hydrolyze lignocellulosic biomass. We also solved the structure of one highly active GH61 protein and find that it is devoid of conserved, closely juxtaposed acidic side chains that could serve as general proton donor and nucleophile/base in a canonical hydrolytic reaction, and we conclude that the GH61 proteins are unlikely to be glycoside hydrolases. Structure-based mutagenesis shows the importance of several conserved residues for GH61 function. By incorporating the gene for one GH61 protein into a com. Trichoderma reesei strain producing high levels of cellulolytic enzymes, we are able to reduce by 2-fold the total protein loading (and hence the cost) required to hydrolyze lignocellulosic biomass.
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22. 22
  Vaaje-Kolstad, G.; Westereng, B.; Horn, S. J.; Liu, Z.; Zhai, H.; So̷rlie, M.; Eijsink, V. G. An oxidative enzyme boosting the enzymatic conversion of recalcitrant polysaccharides. Science 2010, 330, 219– 222, DOI: 10.1126/science.1192231
  22
  An Oxidative Enzyme Boosting the Enzymatic Conversion of Recalcitrant Polysaccharides
  Vaaje-Kolstad, Gustav; Westereng, Bjorge; Horn, Svein J.; Liu, Zhanliang; Zhai, Hong; Sorlie, Morten; Eijsink, Vincent G. H.
  Science (Washington, DC, United States) (2010), 330 (6001), 219-222CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)
  Efficient enzymic conversion of cryst. polysaccharides is crucial for an economically and environmentally sustainable bioeconomy but remains unfavorably inefficient. We describe an enzyme that acts on the surface of cryst. chitin, where it introduces chain breaks and generates oxidized chain ends, thus promoting further degrdn. by chitinases. This enzymic activity was discovered and further characterized by using mass spectrometry and chromatog. sepn. methods to detect oxidized products generated in the absence or presence of H218O or 18O2. There are strong indications that similar enzymes exist that work on cellulose. Our findings not only demonstrate the existence of a hitherto unknown enzyme activity but also provide new avenues toward more efficient enzymic conversion of biomass.
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23. 23
  Forsberg, Z.; Vaaje-Kolstad, G.; Westereng, B.; Bunæs, A. C.; Stenstro̷m, Y.; MacKenzie, A.; So̷rlie, M.; Horn, S. J.; Eijsink, V. G. Cleavage of cellulose by a CBM33 protein. Protein Sci. 2011, 20, 1479– 1483, DOI: 10.1002/pro.689
  23
  Cleavage of cellulose by a CBM33 protein
  Forsberg, Zarah; Vaaje-Kolstad, Gustav; Westereng, Bjorge; Bunaes, Anne C.; Stenstrom, Yngve; MacKenzie, Alasdair; Sorlie, Morten; Horn, Svein J.; Eijsink, Vincent G. H.
  Protein Science (2011), 20 (9), 1479-1483CODEN: PRCIEI; ISSN:1469-896X. (Wiley-Blackwell)
  Bacterial proteins categorized as family 33 carbohydrate-binding modules (CBM33) were recently shown to cleave cryst. chitin, using a mechanism that involves hydrolysis and oxidn. Here, the authors show that some members of the CBM33 family cleave cryst. cellulose as demonstrated by chromatog. and mass spectrometric analyses of sol. products released from Avicel or filter paper on incubation with CelS2, a CBM33-contg. protein from Streptomyces coelicolor A3(2). These enzymes acted synergistically with cellulases and may thus become important tools for efficient conversion of lignocellulosic biomass. Fungal proteins classified as glycoside hydrolase family 61 that are known to act synergistically with cellulases are likely to use a similar mechanism.
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24. 24
  Quinlan, R. J.; Sweeney, M. D.; Lo Leggio, L.; Otten, H.; Poulsen, J. C.; Johansen, K. S.; Krogh, K. B.; Jo̷rgensen, C. I.; Tovborg, M.; Anthonsen, A.; Tryfona, T.; Walter, C. P.; Dupree, P.; Xu, F.; Davies, G. J.; Walton, P. H. Insights into the oxidative degradation of cellulose by a copper metalloenzyme that exploits biomass components. Proc. Natl. Acad. Sci. U. S. A. 2011, 108, 15079– 15084, DOI: 10.1073/pnas.1105776108
  24
  Insights into the oxidative degradation of cellulose by a copper metalloenzyme that exploits biomass components
  Quinlan, R. Jason; Sweeney, Matt D.; Lo Leggio, Leila; Otten, Harm; Poulsen, Jens-Christian N.; Johansen, Katja Salomon; Krogh, Kristian B. R. M.; Jorgensen, Christian Isak; Tovborg, Morten; Anthonsen, Annika; Tryfona, Theodora; Walter, Clive P.; Dupree, Paul; Xu, Feng; Davies, Gideon J.; Walton, Paul H.
  Proceedings of the National Academy of Sciences of the United States of America (2011), 108 (37), 15079-15084, S15079/1-S15079/10CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)
  The enzymic degrdn. of recalcitrant plant biomass is one of the key industrial challenges of the 21st century. Accordingly, there is a continuing drive to discover new routes to promote polysaccharide degrdn. Perhaps the most promising approach involves the application of 'cellulase-enhancing factors', such as those from the glycoside hydrolase (CAZy) GH61 family. Here we show that GH61 enzymes are a unique family of copper-dependent oxidases. We demonstrate that copper is needed for GH61 maximal activity and that the formation of cellodextrin and oxidized cellodextrin products by GH61 is enhanced in the presence of small mol. redox-active cofactors such as ascorbate and gallate. By using ESR spectroscopy and single-crystal X-ray diffraction, the active site of GH61 is revealed to contain a type II copper and, uniquely, a methylated histidine in the copper's coordination sphere, thus providing an innovative paradigm in bioinorg. enzymic catalysis.
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25. 25
  Beeson, W. T.; Phillips, C. M.; Cate, J. H. D.; Marletta, M. A. Oxidative cleavage of cellulose by fungal copper-dependent polysaccharide monooxygenases. J. Am. Chem. Soc. 2011, 134, 890– 892, DOI: 10.1021/ja210657t
  There is no corresponding record for this reference.
26. 26
  Moreau, C.; Tapin-Lingua, S.; Grisel, S.; Gimbert, I.; Le Gall, S.; Petit-Conil, M.; Berrin, J. G.; Cathala, B.; Villares, A. Lytic polysaccharide monooxygenases (LPMOs) facilitate cellulose nanofibrils production. Biotechnol. Biofuels. 2019, 12, 156, DOI: 10.1186/s13068-019-1501-0
  26
  Lytic polysaccharide monooxygenases (LPMOs) facilitate cellulose nanofibrils production
  Moreau Celine; Le Gall Sophie; Cathala Bernard; Villares Ana; Tapin-Lingua Sandra; Grisel Sacha; Gimbert Isabelle; Berrin Jean-Guy; Meyer Valerie; Petit-Conil Michel
  Biotechnology for biofuels (2019), 12 (), 156 ISSN:1754-6834.
  BACKGROUND: Lytic polysaccharide monooxygenases (LPMOs) are copper-dependent enzymes that cleave polysaccharides through an oxidative mechanism. These enzymes are major contributors to the recycling of carbon in nature and are currently used in the biorefinery industry. LPMOs are commonly used in synergy with cellulases to enhance biomass deconstruction. However, there are few examples of the use of monocomponent LPMOs as a tool for cellulose fibrillation. In this work, we took advantage of the LPMO action to facilitate disruption of wood cellulose fibers as a strategy to produce nanofibrillated cellulose (NFC). RESULTS: The fungal LPMO from AA9 family (PaLPMO9E) was used in this study as it displays high specificity toward cellulose and its recombinant production in bioreactor is easily upscalable. The treatment of birchwood fibers with PaLPMO9E resulted in the release of a mixture of C1-oxidized oligosaccharides without any apparent modification in fiber morphology and dimensions. The subsequent mechanical shearing disintegrated the LPMO-pretreated samples yielding nanoscale cellulose elements. Their gel-like aspect and nanometric dimensions demonstrated that LPMOs disrupt the cellulose structure and facilitate the production of NFC. CONCLUSIONS: This study demonstrates the potential use of LPMOs as a pretreatment in the NFC production process. LPMOs weaken fiber cohesion and facilitate fiber disruption while maintaining the crystallinity of cellulose.
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27. 27
  Villares, A.; Moreau, C.; Bennati-Granier, C.; Garajova, S.; Foucat, L.; Falourd, X.; Saake, B.; Berrin, J. G.; Cathala, B. Lytic polysaccharide monooxygenases disrupt the cellulose fibers structure. Sci. Rep. 2017, 7, 40262, DOI: 10.1038/srep40262
  27
  Lytic polysaccharide monooxygenases disrupt the cellulose fibers structure
  Villares, Ana; Moreau, Celine; Bennati-Granier, Chloe; Garajova, Sona; Foucat, Loic; Falourd, Xavier; Saake, Bodo; Berrin, Jean-Guy; Cathala, Bernard
  Scientific Reports (2017), 7 (), 40262CODEN: SRCEC3; ISSN:2045-2322. (Nature Publishing Group)
  Lytic polysaccharide monooxygenases (LPMOs) are a class of powerful oxidative enzymes that breakdown recalcitrant polysaccharides such as cellulose. Here we investigate the action of LPMOs on cellulose fibers. After enzymic treatment and dispersion, LPMO-treated fibers show intense fibrillation. Cellulose structure modifications visualized at different scales indicate that LPMO creates nicking points that trigger the disintegration of the cellulose fibrillar structure with rupture of chains and release of elementary nanofibrils. Investigation of LPMO action using solid-state NMR provides direct evidence of modification of accessible and inaccessible surfaces surrounding the cryst. core of the fibrils. The chains breakage likely induces modifications of the cellulose network and weakens fibers cohesion promoting their disruption. Besides the formation of new initiation sites for conventional cellulases, this work provides the first evidence of the direct oxidative action of LPMOs with the mech. weakening of the cellulose ultrastructure. LPMOs can be viewed as promising biocatalysts for enzymic modification or degrdn. of cellulose fibers.
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28. 28
  Koskela, S.; Wang, S.; Xu, D.; Yang, X.; Li, K.; Berglund, L.; McKee, L. S.; Bulone, V.; Zhou, Q. Lytic polysaccharide monooxygenase (LPMO) mediated production of ultra-fine cellulose nanofibres from delignified softwood fibres. Green Chem. 2019, 21, 5924– 5933, DOI: 10.1039/C9GC02808K
  28
  Lytic polysaccharide monooxygenase (LPMO) mediated production of ultra-fine cellulose nanofibres from delignified softwood fibres
  Koskela, Salla; Wang, Shennan; Xu, Dingfeng; Yang, Xuan; Li, Kai; Berglund, Lars A.; McKee, Lauren S.; Bulone, Vincent; Zhou, Qi
  Green Chemistry (2019), 21 (21), 5924-5933CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
  The prodn. of cellulose nanofibres (CNFs) typically requires harsh chem. and strong mech. fibrillation, both of which have neg. environmental impacts. A possible soln. is offered by lytic polysaccharide monooxygenases (LPMOs), oxidative enzymes that boost cellulose fibrillation. Although the role of LPMOs in oxidative modification of cellulosic substrates is rather well established, their use in the prodn. of cellulose nanomaterials is not fully explored, and the effect of the carbohydrate-binding module (CBM) on nanofibrillation has not yet been reported. Herein, we studied the activity of two LPMOs, one of which was appended to a CBM, on delignified softwood fibers for green and energy-efficient prodn. of CNFs. The CNFs were used to prep. cellulose nanopapers, and the structure and properties of both nanofibres and nanopapers were detd. Both enzymes were able to facilitate nanocellulose fibrillation and increase the colloidal stability of the produced CNFs. However, the CBM-lacking LPMO was more efficient in introducing carboxyl groups (0.53 mmol g-1) on the cellulose fiber surfaces and releasing CNFs with a thinner width (4.3 ± 1.5 nm) from delignified spruce fibers than the modular LPMO (carboxylate content of 0.38 mmol g-1 and nanofibre width of 6.7 ± 2.5 nm) through LPMO-pretreatment followed by mild homogenization. The prepd. nanopapers showed improved mech. properties (tensile strength of 262 MPa and modulus of 16.2 GPa) compared to those obtained by conventional CNF prepn. methods, demonstrating the potential of LPMOs as green alternatives for cellulose nanomaterial prepn.
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29. 29
  Spangler, D.; Rothenburger, S.; Nguyen, K.; Jampani, H.; Weiss, S.; Bhende, S. In vitro antimicrobial activity of oxidized regenerated cellulose against antibiotic-resistant microorganisms. Surg. Infect. (Larchmt) 2003, 4, 255– 262, DOI: 10.1089/109629603322419599
  29
  In vitro antimicrobial activity of oxidized regenerated cellulose against antibiotic-resistant microorganisms
  Spangler Daniel; Rothenburger Stephen; Nguyen Kien; Jampani Hanuman; Weiss Scott; Bhende Shubhangi
  Surgical infections (2003), 4 (3), 255-62 ISSN:1096-2964.
  BACKGROUND: The emergence of multi-drug resistant microorganisms presents a critical problem for patients undergoing surgery. Acidic pH, which is produced by oxidized regenerated cellulose (ORC), is a broad-spectrum physiological detriment to survival of microorganisms known to cause surgical infections. The purpose of this study was to examine the antimicrobial effect of ORC against antibiotic-resistant organisms. METHODS: ORC products were challenged with ATCC reference strains and clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA), methicillin-resistant Staphylococcus epidermidis (MRSE), vancomycin-resistant Enterococcus (VRE), penicillin-resistant Streptococcus pneumoniae (PRSP), and non-resistant ATCC strains of S. aureus and Pseudomonas aeruginosa. Samples of three ORC products (SURGICEL absorbable hemostat, SURGICEL Fibrillar absorbable hemostat, and SURGICEL NU-KNIT absorbable hemostat and identified, respectively, as ORC-R, ORC-F, and ORC-N for this study) were inoculated with challenge organisms in nutrient broth to produce a weight to volume ratio of 15 mg ORC/mL. Plate counts were performed at 0, 1, 6, and 24 h. RESULTS: Antimicrobial activity was seen with all three ORC products against the challenge organisms. Data indicate that antibiotic-resistant microorganisms remain susceptible to the antimicrobial activity of ORC. In testing with nine of 10 bacteria, including four antibiotic-resistant clinical isolates (VRE, MRSA, and PRSP) three-log or greater reductions were seen at 24-h exposure. One ATCC strain of VRE demonstrated some level of resistance to the acidic pH effect. ORC-N showed a three-log reduction with this organism, whereas the reductions with ORC-R and ORC-F were less than one log. CONCLUSION: Since low pH affects a relatively broad-spectrum of bacteria and does not act in a mechanism-specific manner, as do antibiotics, antibiotic-resistant strains of bacteria are unlikely to resist the ORC pH effect. Results of this in vitro assessment support the hypothesis that the antimicrobial activity of ORC is effective against antibiotic-resistant microorganisms.
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30. 30
  Wohlhauser, S.; Delepierre, G.; Labet, M.; Morandi, G.; Thielemans, W.; Weder, C.; Zoppe, J. O. Grafting polymers from cellulose nanocrystals: synthesis, properties and applications. Macromolecules 2018, 51, 6157– 6189, DOI: 10.1021/acs.macromol.8b00733
  30
  Grafting Polymers from Cellulose Nanocrystals: Synthesis, Properties, and Applications
  Wohlhauser, Sandra; Delepierre, Gwendoline; Labet, Marianne; Morandi, Gaelle; Thielemans, Wim; Weder, Christoph; Zoppe, Justin O.
  Macromolecules (Washington, DC, United States) (2018), 51 (16), 6157-6189CODEN: MAMOBX; ISSN:0024-9297. (American Chemical Society)
  Over the past 10 years, the grafting of polymers from the surface of cellulose nanocrystals (CNCs) has gained substantial interest in both academia and industry due to the rapidly growing no. of potential applications of surface-modified CNCs, which range from building blocks in nanocomposites and responsive nanomaterials to antimicrobial agents. CNCs are rod-like nanoparticles that can be isolated from renewable biosources and which exhibit high crystallinity, tunable aspect ratio, high stiffness, and strength. Upon drying, the abundance of surface hydroxyl groups often leads to a degree of irreversible aggregation, as a result of strong hydrogen bonding. Moreover, their relatively hydrophilic character renders CNCs incompatible with hydrophobic media, e.g., nonpolar solvents and polyolefin matrixes. By grafting macromols. from their surface, CNCs can be imparted with surface characteristics and other physicochem. properties that are reminiscent of the grafted polymer. This has allowed the design of nanoscale building blocks whose readily tunable properties are useful for the formation of both colloidal dispersions and solid state materials. In this Perspective, we provide an overview of the morphol. and surface chem. of CNCs and detail various techniques to manipulate their surface chem. via polymer grafting from approaches. Moreover, we explore the most common polymn. techniques that are used to graft polymers from the surface and reducing end groups of CNCs, including surface-initiated ring-opening polymn. (SI-ROP), surface-initiated free (SI-FRP), and controlled (SI-CRP) radical polymn. Finally, we provide insights into some of the emerging applications and conclude with an outlook of future work that would benefit the field.
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31. 31
  Quintana, E.; Roncero, M. B.; Vidal, T.; Valls, C. Cellulose oxidation by Laccase-TEMPO treatments. Carbohydr. Polym. 2017, 157, 1488– 1495, DOI: 10.1016/j.carbpol.2016.11.033
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  Cellulose oxidation by Laccase-TEMPO treatments
  Quintana, Elisabet; Roncero, M. Blanca; Vidal, Teresa; Valls, Cristina
  Carbohydrate Polymers (2017), 157 (), 1488-1495CODEN: CAPOD8; ISSN:0144-8617. (Elsevier Ltd.)
  In this work, laccase-TEMPO (Lac-T) treatments were applied to bleached com. dissolving pulp in order to introduce carbonyl and carboxyl groups, which were found to improve dry and wet strength-related properties. Also the soly. behavior towards xanthate reactions was assessed. The effect of a refining step (R) before the oxidative treatment, the absence or presence of oxygen pressure, TEMPO dose (2 or 8% oven dried pulp) and reaction time (8 or 20 h) were thoroughly examd. Treatments conducted in the presence of oxygen pressure exhibited greater amt. of functional groups. Introducing a pre-refining treatment resulted in similar functional groups but higher wet strength was achieved. Specifically, a high W/D strength ratio was obsd., indicating that wet strength-related property was satisfactorily developed. Besides the fact that all Lac-T treatments caused severe cellulose degrdn., no fiber strength loss was detected. In fact, all oxidized samples presented higher Wet Zero-Span Tensile Strength, mainly in R+ Lac-T (O2) sample, which suggested the formation of hemiacetal linkages between the new introduced aldehyde groups and available free hydroxyl groups resulting from fibrillation.
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32. 32
  Vaaje-Kolstad, G.; Forsberg, Z.; Loose, J. S.; Bissaro, B.; Eijsink, V. G. Structural diversity of lytic polysaccharide monooxygenases. Curr. Opin. Struct. Biol. 2017, 44, 67– 76, DOI: 10.1016/j.sbi.2016.12.012
  32
  Structural diversity of lytic polysaccharide monooxygenases
  Vaaje-Kolstad, Gustav; Forsberg, Zarah; Loose, Jennifer S. M.; Bissaro, Bastien; Eijsink, Vincent G. H.
  Current Opinion in Structural Biology (2017), 44 (), 67-76CODEN: COSBEF; ISSN:0959-440X. (Elsevier Ltd.)
  A review. Lytic polysaccharide monooxygenases (LPMOs) catalyze the oxidative cleavage of glycosidic bonds and represent a promising resource for development of industrial enzyme cocktails for biomass processing. LPMOs show high sequence and modular diversity and are known, so far, to cleave insol. substrates such as cellulose, chitin and starch, as well as hemicelluloses such as beta-glucan, xyloglucan and xylan. All LPMOs share a catalytic histidine brace motif to bind copper, but differ strongly when it comes to the nature and arrangement of residues on the substrate-binding surface. In recent years, the no. of available LPMO structures has increased rapidly, including the first structure of an enzyme-substrate complex. The insights gained from these structures is reviewed below.
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33. 33
  Wang, D.; Li, J.; Salazar-Alvarez, G.; McKee, L. S.; Srivastava, V.; Sellberg, J. A.; Bulome, V.; Hsieh, Y. S. Y. Production of functionalised chitins assisted by fungal lytic polysaccharide monooxygenase. Green Chem. 2018, 20, 2091– 2100, DOI: 10.1039/C8GC00422F
  33
  Production of functionalised chitins assisted by fungal lytic polysaccharide monooxygenase
  Wang, Damao; Li, Jing; Salazar-Alvarez, German; McKee, Lauren S.; Srivastava, Vaibhav; Sellberg, Jonas A.; Bulone, Vincent; Hsieh, Yves S. Y.
  Green Chemistry (2018), 20 (9), 2091-2100CODEN: GRCHFJ; ISSN:1463-9262. (Royal Society of Chemistry)
  The gene CCT67099 from Fusarium fujikuroi was shown to encode a novel enzyme from the Lytic Polysaccharide Monooxygenase (LPMO) Family AA11. The gene was expressed and a truncated version of the enzyme, designated as FfAA11, was purified from the periplasmic space of Escherichia coli cells at high yield. FfAA11 exhibited oxidative activity against α- and β-chitins, as well as lobster shells. Under optimized conditions, FfAA11 introduced 35 nmol of carboxylate (COO-) moieties per mg of α-chitin. These carboxylate groups were introduced onto the chitin surface under mild enzymic oxidn. conditions in an aq. soln. without changes to the crystallinity of the chitin fibers. FfAA11 was also combined with a simple and environmentally friendly chem. method that transforms recalcitrant chitins into desirable functionalised (nano)materials. The use of ethyl(hydroxyimino)cyanoacetate (Oxyma)-assisted click chem. allowed the rapid modification of the surface of FfAA11-oxidized chitins, with a fluorescent probe, a peptide, and gold nanoparticles. The chem. steps performed, including the FfAA11 oxidase treatment and surface chem. modification, were achieved without the prodn. of any toxic byproducts or waste org. solvents. This approach represents a novel method for the greener prodn. of chitin-based biomaterials.
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34. 34
  Valls, C.; Pastor, F. I. J.; Roncero, M. B.; Vidal, T.; Diaz, P.; Martinez, J.; Valenzuela, S. V. Assessing the enzymatic effects of cellulases and LPMO in improving mechanical fibrillation of cotton linters. Biotechnol. Biofuels 2019, 12, 161, DOI: 10.1186/s13068-019-1502-z
  34
  Assessing the enzymatic effects of cellulases and LPMO in improving mechanical fibrillation of cotton linters
  Valls Cristina; Pastor F I Javier; Diaz Pilar; Martinez Josefina; Valenzuela Susana V; Valls Cristina; Roncero M Blanca; Vidal Teresa
  Biotechnology for biofuels (2019), 12 (), 161 ISSN:1754-6834.
  BACKGROUND: The increasing interest in replacing petroleum-based products by more sustainable materials in the packaging sector gives relevance to cellulose as a biodegradable natural resource. Moreover, its properties can be modified physically, chemically or biotechnologically in order to obtain new bioproducts. Refined cotton linters with high cellulose content were treated with hydrolytic (cellulases) and oxidative (LPMO and Laccase_Tempo) enzymes to evaluate their effect on fibre properties and in improving mechanical fibrillation. RESULTS: Cellulases released cellooligosaccharides, reducing fibre length and partially degrading cellulose. They also improved mechanical fibrillation yielding up to 18% of nanofibrillated cellulose (NFC). LPMO introduced a slight amount of COOH groups in cellulose fibres, releasing cellobionic acid to the effluents. The action of cellulases was improved after LPMO treatment; however, the COOH groups created disappeared from fibres. After mechanical fibrillation of LPMO-cellulase-treated cotton linters a 23% yield of NFC was obtained. Laccase_Tempo treatment also introduced COOH groups in cellulose fibres from cotton, yielding 10% of NFC. Degree of polymerization was reduced by Laccase_Tempo, while LPMO treatment did not significantly affect it but produced a higher reduction in fibre length. The combined treatment with LPMO and cellulase provided films with higher transparency (86%), crystallinity (92%), smoothness and improved barrier properties to air and water than films casted from non-treated linters and from commercial NFC. CONCLUSIONS: The combined enzymatic treatment with LPMO and cellulases boosted mechanical fibrillation of cotton linters, improving the NFC production and providing bioproducts with high transparency and high barrier properties.
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35. 35
  Hrůzová, K.; Matsakas, L.; Karnaouri, A.; Norén, F.; Rova, U.; Christakopoulos, P. Second-generation biofuel production from the marine filter feeder Ciona intestinalis. ACS Sustainable Chem. Eng. 2020, 8, 8373– 8380, DOI: 10.1021/acssuschemeng.0c02417
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  Second-Generation Biofuel Production from the Marine Filter Feeder Ciona intestinalis
  Hruzova, Katerina; Matsakas, Leonidas; Karnaouri, Anthi; Noren, Fredrik; Rova, Ulrika; Christakopoulos, Paul
  ACS Sustainable Chemistry & Engineering (2020), 8 (22), 8373-8380CODEN: ASCECG; ISSN:2168-0485. (American Chemical Society)
  Biofuels are essential for transitioning to a sustainable society. This switch can be achieved by introducing novel feedstocks and technologies for efficient and economically feasible biofuel prodn. Second-generation biofuels are particularly advantageous, as they are produced from nonedible lignocellulosic biomass derived primarily from agricultural byproducts. Ciona intestinalis, a marine filter feeder, is cultivated to produce fish feed from the invertebrate's inner tissue body. This process generates also vast amts. of a renewable side stream, namely the tunicate's external cellulose-rich tunic. The aim of the present study was to evaluate the potential of the C. intestinalis tunic as a novel feedstock for bioethanol prodn. For this purpose, organosolv fractionation of the tunic was optimized to increase cellulose content. Enzymic saccharification of the pretreated biomass was assessed to identify the most promising materials, which were subsequently utilized as carbon source in fermn. trials. Under optimal conditions, a titer of 38.7 g/L of ethanol, with a yield of 78.3% of the max. theor., was achieved. To the best of our knowledge, this is the first report whereby organosolv pretreated tunic biomass is valorized toward bioethanol prodn.; the current work paves the way for incorporating tunicates in bioconversion processes for the generation of biofuels and other biobased chems. The tunic of Ciona intestinalis is a cellulose-rich waste stream, which represents a promising feedstock for second-generation bioethanol prodn.
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36. 36
  Sluiter, J. B.; Ruiz, R. O.; Scarlata, C. J.; Sluiter, A. D.; Templeton, D. W. Compositional analysis of lignocellulosic feedstocks. 1. Review and description of methods. J. Agric. Food Chem. 2010, 58, 9043– 9053, DOI: 10.1021/jf1008023
  36
  Compositional Analysis of Lignocellulosic Feedstocks. 1. Review and Description of Methods
  Sluiter, Justin B.; Ruiz, Raymond O.; Scarlata, Christopher J.; Sluiter, Amie D.; Templeton, David W.
  Journal of Agricultural and Food Chemistry (2010), 58 (16), 9043-9053CODEN: JAFCAU; ISSN:0021-8561. (American Chemical Society)
  A review. As interest in lignocellulosic biomass feedstocks for conversion into transportation fuels grows, the summative compositional anal. of biomass, or plant-derived material, becomes ever more important. The sulfuric acid hydrolysis of biomass has been used to measure lignin and structural carbohydrate content for more than 100 years. Researchers have applied these methods to measure the lignin and structural carbohydrate contents of woody materials, est. the nutritional value of animal feed, analyze the dietary fiber content of human food, compare potential biofuels feedstocks, and measure the efficiency of biomass-to-biofuels processes. The purpose of this paper is to review the history and lineage of biomass compositional anal. methods based on a sulfuric acid hydrolysis. These methods have become the de facto procedure for biomass compositional anal. The paper traces changes to the biomass compositional anal. methods through time to the biomass methods currently used at the National Renewable Energy Lab. (NREL). The current suite of lab. anal. procedures (LAPs) offered by NREL is described, including an overview of the procedures and methodologies and some common pitfalls. Suggestions are made for continuing improvement to the suite of analyses.
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37. 37
  Karnaouri, A.; Muraleedharan, M. N.; Dimarogona, M.; Topakas, E.; Rova, U.; Sandgren, M.; Christakopoulos, P. Recombinant expression of thermostable processive MtEG5 endoglucanase and its synergism with MtLPMO from Myceliophthora thermophila during the hydrolysis of lignocellulosic substrates. Biotechnol. Biofuels 2017, 10, 126, DOI: 10.1186/s13068-017-0813-1
  37
  Recombinant expression of thermostable processive MtEG5 endoglucanase and its synergism with MtLPMO from Myceliophthora thermophila during the hydrolysis of lignocellulosic substrates
  Karnaouri, Anthi; Muraleedharan, Madhu Nair; Dimarogona, Maria; Topakas, Evangelos; Rova, Ulrika; Sandgren, Mats; Christakopoulos, Paul
  Biotechnology for Biofuels (2017), 10 (), 126/1-126/17CODEN: BBIIFL; ISSN:1754-6834. (BioMed Central Ltd.)
  Background: Filamentous fungi are among the most powerful cellulolytic organisms in terrestrial ecosystems. To perform the degrdn. of lignocellulosic substrates, these microorganisms employ both hydrolytic and oxidative mechanisms that involve the secretion and synergism of a wide variety of enzymes. Interactions between these enzymes occur on the level of saccharification, i.e., the release of neutral and oxidized products, but sometimes also reflected in the substrate liquefaction. Although the synergism regarding the yield of neutral sugars has been extensively studied, further studies should focus on the oxidized sugars, as well as the effect of enzyme combinations on the viscosity properties of the substrates. Results: In the present study, the heterologous expression of an endoglucanase (EG) and its combined activity together with a lytic polysaccharide monooxygenase (LPMO), both from the thermophilic fungus Myceliophthora thermophila, are described. The EG gene, belonging to the glycoside hydrolase family 5, was functionally expressed in the methylotrophic yeast Pichia pastoris. The produced MtEG5A (75 kDa) featured remarkable thermal stability and showed high specific activity on microcryst. cellulose compared to CMC, which is indicative of its processivity properties. The enzyme was capable of releasing high amts. of cellobiose from wheat straw, birch, and spruce biomass. Addn. of MtLPMO9 together with MtEG5A showed enhanced enzymic hydrolysis yields against regenerated amorphous cellulose (PASC) by improving the release not only of the neutral but also of the oxidized sugars. Assessment of activity of MtEG5A on the redn. of viscosity of PASC and pretreated wheat straw using dynamic viscosity measurements revealed that the enzyme is able to perform liquefaction of the model substrate and the natural lignocellulosic material, while when added together with MtLPMO9, no further synergistic effect was obsd. Conclusions: The endoglucanase MtEG5A from the thermophilic fungus M. thermophila exhibited excellent properties that render it a suitable candidate for use in biotechnol. applications. Its strong synergism with LPMO was reflected in sugars release, but not in substrate viscosity redn. Based on the level of oxidative sugar formation, this is the first indication of synergy between LPMO and EG reported.
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38. 38
  Lowry, O. H.; Rosebrough, N. J.; Lewis Farr, A.; Randall, R. J. Protein Measurement with the Folin phenol reagent. J. Biol. Chem. 1951, 193, 265– 275
  38
  Protein measurement with the Folin phenol reagent
  Lowry, Oliver H.; Rosebrough, Nira J.; Farr, A. Lewis; Randall, Rose J.
  Journal of Biological Chemistry (1951), 193 (), 265-75CODEN: JBCHA3; ISSN:0021-9258.
  cf. C.A. 41, 1271h. Proteins were detd. with the Folin phenol reagent after alk. Cu treatment. The method is as sensitive as with Nessler reagent, yet requires no digestion. It is 10-20 times more sensitive than detn. of the ultraviolet absorption at λ = 280 mμ and is more specific. It is several fold more sensitive than the ninhydrin reaction and 100 times more sensitive than the biuret reaction. Two major disadvantages are: the amt. of color varies with different proteins; the color is not strictly proportional to concn. Few substances cause serious interference. Uric acid, guanine, and xanthine react with Folin reagent. The method is useful for following enzyme fractionation, detg. mixed tissue proteins, detn. of very small amts. of protein, or detg. highly dild. protein, or protein in colored solns. or in the presence of N-contg. material.
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39. 39
  Schulz, B. L.; Packer, N. H.; Karlsson, N. G. Small-scale analysis of O-linked oligosaccharides from glycoproteins and mucins separated by gel electrophoresis. Anal. Chem. 2002, 74, 6088– 6097, DOI: 10.1021/ac025890a
  39
  Small-scale analysis of O-linked oligosaccharides from glycoproteins and mucins separated by gel electrophoresis
  Schulz, Benjamin L.; Packer, Nicolle H.; Karlsson, Niclas G.
  Analytical Chemistry (2002), 74 (23), 6088-6097CODEN: ANCHAM; ISSN:0003-2700. (American Chemical Society)
  A technique with subpicomolar sensitivity was developed for analyzing O-linked oligosaccharides released from glycoproteins sepd. by gel electrophoresis. The protocol involves gel electrophoresis, electroblotting to poly(vinylidene fluoride) membrane, reductive β-elimination, and anal. of released oligosaccharides by liq. chromatog. coupled to neg. ion electrospray mass spectrometry. It was also found that N-linked oligosaccharides could be recovered under the same conditions, found both as free oligosaccharides and as distinct glycopeptides created from reductive cleavage of the protein backbone, giving some information on site-specific glycosylation. The method was used to demonstrate that the difference between human α-2HS-glycoprotein isoforms sepd. by 2D-gel electrophoresis was partially due to sialylation of both O-linked and N-linked oligosaccharides. It was also shown that both acidic and neutral oligosaccharides could be recovered and analyzed simultaneously from high mol. mass (200 000-5 000 000 Da) highly glycosylated mucin glycoproteins collected from small intestine and saliva and sepd. by SDS-agarose/polyacrylamide composite gels. Mass spectrometric data not only gave information about the mass distribution of the heterogeneous mixts. of oligosaccharides from [M - xH]x- ions but also gave information about the isomeric heterogeneity of the oligosaccharides from their resoln. by porous graphitized carbon chromatog. Tandem mass spectrometry was explored as a technique for distinguishing between oligosaccharide isomers with different sequences and also between oligosaccharides with the same sequence but with different linkage configurations.
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40. 40
  Bondeson, D.; Mathew, A.; Oksman, K. Optimization of the isolation of nanocrystals from microcrystalline cellulose by acid hydrolysis. Cellulose 2006, 13, 171– 180, DOI: 10.1007/s10570-006-9061-4
  40
  Optimization of the isolation of nanocrystals from microcrystalline cellulose by acid hydrolysis
  Bondeson, Daniel; Mathew, Aji; Oksman, Kristiina
  Cellulose (Dordrecht, Netherlands) (2006), 13 (2), 171-180CODEN: CELLE8; ISSN:0969-0239. (Springer)
  The objective of this work was to find a rapid, high-yield process to obtain an aq. stable colloid suspension of cellulose nanocrystals/whiskers. Large quantities are required since these whiskers are designed to be extruded into polymers in the prodn. of nano-biocomposites. Microcryst. cellulose (MCC), derived from Norway spruce (Picea abies), was used as the starting material. The processing parameters have been optimized by using response surface methodol. The factors that varied during the process were the concn. of MCC and sulfuric acid, the hydrolysis time and temp., and the ultrasonic treatment time. Responses measured were the median size of the cellulose particles/whiskers and yield. The surface charge as calcd. from conductometric titrn., microscopic examns. (optical and transmission electron microscopy), and observation of birefringence were also investigated in order to det. the outcome (efficiency) of the process. With a sulfuric acid concn. of 63.5% (wt./wt.), it was possible to obtain cellulose nanocrystals/whiskers with a length between 200 and 400 nm and a width less than 10 nm in approx. 2 h with a yield of 30% (of initial wt.).
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41. 41
  Klarhöfer, L.; Roos, B.; Viöl, W.; Höfft, O.; Dieckhoff, S.; Kempter, V.; Maus-Friedrichs, W. Valence band spectroscopy on lignin. Holzforschung 2008, 62. DOI: 10.1515/HF.2008.116
  There is no corresponding record for this reference.
42. 42
  Krischok, S.; Höfft, O.; Günster, J.; Stultz, J.; Goodman, D. W.; Kempter, V. H2O interaction with bare and Li-precovered TiO2: Studies with electron spectroscopies (MIES and UPS (HeI and II)). Surf. Sci. 2001, 495, 8– 18, DOI: 10.1016/S0039-6028(01)01570-9
  42
  H2O interaction with bare and Li-precovered TiO2. Studies with electron spectroscopies (MIES and UPS(HeI and II))
  Krischok, S.; Hofft, O.; Gunster, J.; Stultz, J.; Goodman, D. W.; Kempter, V.
  Surface Science (2001), 495 (1-2), 8-18CODEN: SUSCAS; ISSN:0039-6028. (Elsevier Science B.V.)
  TiO2(1 1 0) single crystals and TiO2 thin films on Mo(1 1 0), bare and precovered by Li atoms, were exposed to water at 120 K. During the adsorption process metastable impact electron spectroscopy (MIES) and UV photoemission spectroscopy (UPS)(HeI and II) spectra were collected in situ. Spectroscopic and temp.-programmed desorption data were obtained during the annealing of water multilayers grown at 120 K. For the adsorption on the bare TiO2 surface we conclude that an initial dissociative adsorption at defect sites is followed by mol. adsorption up to multilayer formation. From the exposure dependence of the MIES and UPS signals we conclude that, even before the completion of the first adlayer, no isolated water mols. are sampled, and strong lateral interaction between adjacent adsorbates stabilizes mol. water.On TiO2(1 1 0), precovered by about 1 ML of Li atoms, water is adsorbed dissociatively both at 120 K and at room temp. until the first, mixed layer consisting of Li and OH species, is completed. On top of the first layer addnl. water is adsorbed molecularly. Annealing expts. show that the first layer remains intact when the second layer forms.
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43. 43
  Hercules, D. M.; Cox, L. E.; Onisick, S.; Nichols, G. D.; Carver, J. C. Electron spectroscopy (ESCA). Use for trace analysis. Anal. Chem. 1973, 45, 1973– 1975, DOI: 10.1021/ac60333a037
  43
  Electron spectroscopy (ESCA). Use for trace analysis
  Hercules, David M.; Cox, Lawrence E.; Onisick, Stephen; Nichols, Gary D.; Carver, James C.
  Analytical Chemistry (1973), 45 (11), 1973-5CODEN: ANCHAM; ISSN:0003-2700.
  For detn. by ESCA, trace metals were collected by passing sample solns. through glass fiber disks coated with dithiocarbamate chelating groups. To prep. the disks, glass fibers were treated with 4% Dow-Corning Z-6020 silylizing reagent. For conversion to dithiocarbamate, the silylized glass was refluxed in 1M NaOH-1.5M CS2 in EtOH. Detection limits were ∼10 ppb for Pb, Ca, Tl, and Hg. For quant. anal., an internal std. metal can be added to the sample soln. and collected on the disks.
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44. 44
  Nam, S.; French, A. D.; Condon, B. D.; Concha, M. Segal crystallinity index revisited by the simulation of X-ray diffraction patterns of cotton cellulose Iβ and cellulose II. Carbohydr. Polym. 2016, 135, 1– 9, DOI: 10.1016/j.carbpol.2015.08.035
  44
  Segal crystallinity index revisited by the simulation of X-ray diffraction patterns of cotton cellulose Iβ and cellulose II
  Nam, Sunghyun; French, Alfred D.; Condon, Brian D.; Concha, Monica
  Carbohydrate Polymers (2016), 135 (), 1-9CODEN: CAPOD8; ISSN:0144-8617. (Elsevier Ltd.)
  The Segal method ests. the amorphous fraction of cellulose Iβ materials simply based on intensity at 18° 2θ in an X-ray diffraction pattern and was extended to cellulose II using 16° 2θ intensity. To address the dependency of Segal amorphous intensity on crystal size, cellulose polymorph, and the degree of polymorphic conversion, we simulated the diffraction patterns of cotton celluloses (Iβ and II) and compared the simulated amorphous fractions with the Segal values. The diffraction patterns of control and mercerized cottons, resp., were simulated with perfect crystals of cellulose Iβ (1.54° FWHM) and cellulose II (2.30° FWHM) as well as 10% and 35% amorphous celluloses. Their Segal amorphous fractions were 15% and 31%, resp. The higher Segal amorphous fraction for control cotton was attributed to the peak overlap. Although the amorphous fraction was set in the simulation, the peak overlap induced by the increase of FWHM further enhanced the Segal amorphous intensity of cellulose Iβ. For cellulose II, the effect of peak overlap was smaller; however the lower reflection of the amorphous cellulose scattering in its Segal amorphous location resulted in smaller Segal amorphous fractions. Despite this underestimation, the relatively good agreement of the Segal method with the simulation for mercerized cotton was attributed to the incomplete conversion to cellulose II. The (1 -1 0) and (1 1 0) peaks of cellulose Iβ remained near the Segal amorphous location of cellulose II for blends of control and mercerized cotton fibers.
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45. 45
  Thoresen, P. P.; Matsakas, L.; Rova, U.; Christakopoulos, P. Recent advances in organosolv fractionation: Towards biomass fractionation technology of the future. Bioresour. Technol. 2020, 306, 123189, DOI: 10.1016/j.biortech.2020.123189
  45
  Recent advances in organosolv fractionation: Towards biomass fractionation technology of the future
  Thoresen, Petter Paulsen; Matsakas, Leonidas; Rova, Ulrika; Christakopoulos, Paul
  Bioresource Technology (2020), 306 (), 123189CODEN: BIRTEB; ISSN:0960-8524. (Elsevier Ltd.)
  A review. Organosolv treatment is among the most promising strategies for valorising lignocellulosic biomass and could facilitate the transition towards enhanced utilization of renewable feedstocks. However, issues such as inefficient solvent recycle and fractionation has to be overcome. The present review aims to address these issues and discuss the role of the components present during organosolv treatment and their influence on the overall process. Thus, the review focuses not only on how the choice of solvent and catalyst affects lignocellulosic fractionation, but also on how the choice of treatment liquor influences the possibility for solvent recycling and product isolation. Several org. solvents have been investigated in combination with water and acid/base catalysts; however, the lack of a holistic approach often compromises the performance of the different operational units. Thus, an economically viable organosolv process should optimize biomass fractionation, product isolation, and solvent recycling.
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46. 46
  Kalogiannis, K. G.; Karnaouri, A.; Michailof, C.; Tzika, A. M.; Asimakopoulou, G.; Topakas, E.; Lappas, A. A. OxiOrganosolv: A novel acid free oxidative organosolv fractionation for lignocellulose fine sugar streams. Bioresour. Technol. 2020, 313, 123599, DOI: 10.1016/j.biortech.2020.123599
  46
  OxiOrganosolv: A novel acid free oxidative organosolv fractionation for lignocellulose fine sugar streams
  Kalogiannis, Konstantinos G.; Karnaouri, Anthi; Michailof, Chrysoula; Tzika, Anna Maria; Asimakopoulou, Georgia; Topakas, Evangelos; Lappas, Angelos A.
  Bioresource Technology (2020), 313 (), 123599CODEN: BIRTEB; ISSN:0960-8524. (Elsevier Ltd.)
  The valorization of lignocellulosic biomass towards the prodn. of value-added products requires an efficient pretreatment/fractionation step. In this work we present a novel, acid-free, mildly oxidative organosolv delignification process -OxiOrganosolv- which employs oxygen gas to depolymerize and remove lignin. The results demonstrate that the OxiOrganosolv process achieved lignin removal as high as 97% in a single stage, with a variety of solvents; it was also efficient in delignifying both beechwood (hardwood) and pine (softwood), a task in which organosolv pretreatments have failed in the past. Minimal amts. of sugar degrdn. products were detected, while cellulose recovery was ∼100% in the solid pulp. Enzymic hydrolysis of pulps showed >80 wt% cellulose conversion to glucose. Overall, the OxiOrganosolv pretreatment has significant advantages, including high delignification efficiency of hardwood and softwood biomass, absence of acid homogeneous catalysis and all corresponding challenges involved, and close to zero losses of sugars to degrdn. products.
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47. 47
  Mantanis, G. I.; Young, R. A.; Rowell, R. M. Swelling of compressed cellulose fiber webs in organic liquids. Cellulose 1995, 2, 1– 22, DOI: 10.1007/BF00812768
  47
  Swelling of compressed cellulose fiber webs in organic liquids
  Mantanis, G. I.; Young, R. A.; Rowell, R. M.
  Cellulose (London) (1995), 2 (1), 1-22CODEN: CELLE8; ISSN:0969-0239. (Chapman & Hall)
  Max. liq.-holding capacities of various compressed fibers in water and in a series of various org. liqs. were investigated. The max. liq.-holding capacity vs. bulk d. relationships gave polynomial curves, generally with a peak. Good relative correlations for cellulose, compressed fiber pellets and wood were found for the series of liqs. tested. In general, liqs. that swelled wood to a low-to-medium range (≤6%) did not swell appreciably α-cellulose and sulfite pulp, whereas good-to-excellent wood-swelling agents swelled all of the fibers very significantly. Also, the hydrogen-bonding parameter of the swelling liq. was the most important factor. The swelling rate of various compressed fiber systems in org. liqs. was dramatically increased by raising the temp. Activation energies and molar vol. of the swelling liq. were linearly correlated.
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48. 48
  Sannigrahia, P.; Miller, S. J.; Ragauskas, A. J. Effects of organosolv pretreatment and enzymatic hydrolysis on cellulose structure and crystallinity in Loblolly pine. Carbohydr. Res. 2010, 345, 965– 970, DOI: 10.1016/j.carres.2010.02.010
  There is no corresponding record for this reference.
49. 49
  Levasseur, A.; Drula, E.; Lombard, V.; Coutinho, P. M.; Henrissat, B. Expansion of the enzymatic repertoire of the CAZy database to integrate auxiliary redox enzymes. Biotechnol. Biofuels 2013, 6, 41, DOI: 10.1186/1754-6834-6-41
  49
  Expansion of the enzymatic repertoire of the CAZy database to integrate auxiliary redox enzymes
  Levasseur, Anthony; Drula, Elodie; Lombard, Vincent; Coutinho, Pedro M.; Henrissat, Bernard
  Biotechnology for Biofuels (2013), 6 (), 41CODEN: BBIIFL; ISSN:1754-6834. (BioMed Central Ltd.)
  Background: Since its inception, the carbohydrate-active enzymes database (CAZy;) has described the families of enzymes that cleave or build complex carbohydrates, namely the glycoside hydrolases (GH), the polysaccharide lyases (PL), the carbohydrate esterases (CE), the glycosyltransferases (GT) and their appended non-catalytic carbohydrate-binding modules (CBM). The recent discovery that members of families CBM33 and family GH61 are in fact lytic polysaccharide monooxygenases (LPMO), demands a reclassification of these families into a suitable category. Results: Because lignin is invariably found together with polysaccharides in the plant cell wall and because lignin fragments are likely to act in concert with (LPMO), we have decided to join the families of lignin degrdn. enzymes to the LPMO families and launch a new CAZy class that we name "Auxiliary Activities" in order to accommodate a range of enzyme mechanisms and substrates related to lignocellulose conversion. Comparative analyses of these auxiliary activities in 41 fungal genomes reveal a pertinent division of several fungal groups and subgroups combining their phylogenetic origin and their nutritional mode (white vs. brown rot). Conclusions: The new class introduced in the CAZy database extends the traditional CAZy families, and provides a better coverage of the full extent of the lignocellulose breakdown machinery.
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50. 50
  Silva, C. d. O. G.; Teixeira, T. S.; Rodrigues, K. B.; Souza, A. A.; Monclaro, A. V.; Mendes, T. D. Combination of MALDI-TOF MS and UHPLC-ESI-MS for the characterization of lytic polysaccharide monooxygenase activity. Anal. Methods 2020, 12, 149– 161, DOI: 10.1039/c9ay01774g
  50
  Combination of MALDI-TOF MS and UHPLC-ESI-MS for the characterization of lytic polysaccharide monooxygenase activity
  Silva, Caio de Oliveira Gorgulho; Teixeira, Tallyta Santos; Rodrigues, Kelly Barreto; Souza, Amanda Araujo; Monclaro, Antonielle Vieira; Mendes, Thais Demarchi; Ribeiro, Jose Antonio de Aquino; Goncalves de Siqueira, Felix; Favaro, Leia Cecilia de Lima; Abdelnur, Patricia Verardi
  Analytical Methods (2020), 12 (2), 149-161CODEN: AMNEGX; ISSN:1759-9679. (Royal Society of Chemistry)
  Lytic polysaccharide monooxygenases (LPMOs) are redox enzymes of high biotechnol. interest due to their capacity to degrade recalcitrant polysaccharides, such as cellulose, by an oxidative mechanism. The characterization of LPMOs is challenging since they generate a variety of catalytic products which include native oligosaccharides (non-oxidized) and oligosaccharides oxidized at the reducing end (C1 position), the non-reducing end (C4 position), or both ends, with different ds.p. Moreover, oxidized products exist in equil. with their hydrated forms, which further complicates their identification. The lack of com. anal. stds. for all these possible forms of oxidized oligosaccharides and the low concn. of these products make LPMO functional characterization dependent on advanced mass spectrometry techniques capable of identifying the profile of oxidized products. Here, a new approach for the characterization of cellulose-active LPMOs based on the combination of MALDI-TOF MS and hydrophilic interaction UHPLC-ESI-MS was proposed and optimized. The LPMO TrAA9A from Trichoderma reesei was used as a model enzyme to develop and test the MS methods. MALDI-TOF MS and UHPLC-ESI-MS methods were both capable of identifying putative C1, C4 and C1/C4 oxidized cello-oligosaccharides as well as their native counterparts generated after cellulose treatment with LPMO, which allows their utilization to characterize type I (C1-oxidizer), type II (C4-oxidizer) and type III (C1- and C4-oxidizer) LPMOs. Moreover, both methods were complementary since MALDI-TOF MS was capable of detecting oligosaccharides with higher ds.p. (DP3-DP10), while UHPLC-ESI-MS allowed the evaluation of smaller oligosaccharides (DP1-DP5). The combined use of both methods offers a comprehensive description of LPMO catalytic products.
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51. 51
  Zhao, Y.; Li, J. Ascidian bioresources: common and variant chemical compositions and exploitation strategy – examples of Halocynthia roretzi, Styela plicata, Ascidia sp. and Ciona intestinalis. Z. Naturforschung C 2016, 71, 165– 180, DOI: 10.1515/znc-2016-0012
  51
  Ascidian bioresources: common and variant chemical compositions and exploitation strategy - examples of Halocynthia roretzi, Styela plicata, Ascidia sp. and Ciona intestinalis
  Zhao, Yadong; Li, Jiebing
  Zeitschrift fuer Naturforschung, C: Journal of Biosciences (2016), 71 (5-6), 165-180CODEN: ZNCBDA; ISSN:1865-7125. (Walter de Gruyter GmbH)
  To explore abundant marine ascidian bioresources, four species from two orders have been compared in their chem. compns. After a universal sepn. of the animal body into two fractions, all tunics have been found rich in carbohydrate contents, while all inner body tissues are richer in proteins. Cellulose is present almost exclusively in the tunics and more in the order Stolidobranchia, while more sulfated polysaccharides are present in Phlebobranchia species. Almost all proteins are collagens with a high essential amino acid index and high delicious amino acid (DAA) content. All fractions also have high contents of good-quality fatty acids and trace minerals but low toxic element contents, with different sterols and glycosaminoglycans. There are species-specific characteristics obsd. for vanadium accumulation and sterol structures which are also meaningful for ascidian chemotaxonomy and resource exploitation. It is suggested that in addn. to the present utilizations of tunics for cellulose prodn. and of some species' inner body tissues as human food, one should explore all species' inner body tissues as human foods and all tunics as food or animal feed with the contained cellulose as dietary fiber. Collagens, sulfated polysaccharides, glycosaminoglycans, sterols and trace elements could be explored as byproducts for, e.g. pharmaceutical and chem. industries.
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52. 52
  Eibinger, M.; Ganner, T.; Bubner, P.; Rošker, S.; Kasciddvgdgracher, D.; Haltrich, D.; Ludwig, R.; Plank, H.; Nidetzky, B. Cellulose surface degradation by a lytic polysaccharide monooxygenase and its effect on cellulase hydrolytic efficiency. J. Biol. Chem. 2014, 289, 35929– 35938, DOI: 10.1074/jbc.M114.602227
  52
  Cellulose surface degradation by a lytic polysaccharide monooxygenase and its effect on cellulase hydrolytic efficiency
  Eibinger, Manuel; Ganner, Thomas; Bubner, Patricia; Rosker, Stephanie; Kracher, Daniel; Haltrich, Dietmar; Ludwig, Roland; Plank, Harald; Nidetzky, Bernd
  Journal of Biological Chemistry (2014), 289 (52), 35929-35938CODEN: JBCHA3; ISSN:0021-9258. (American Society for Biochemistry and Molecular Biology)
  Lytic polysaccharide monooxygenase (LPMO) represents a unique principle of oxidative degrdn. of recalcitrant insol. polysaccharides. Used in combination with hydrolytic enzymes, LPMO appears to constitute a significant factor of the efficiency of enzymic biomass depolymn. LPMO activity on different cellulose substrates has been shown from the slow release of oxidized oligosaccharides into soln., but an immediate and direct demonstration of the enzyme action on the cellulose surface is lacking. The specificity of LPMO for degrading ordered cryst. and unordered amorphous cellulose material of the substrate surface is also unknown. Here, the authors show by fluorescent dye adsorption analyzed with confocal laser scanning microscopy that a LPMO (from Neurospora crassa) introduces carboxyl groups primarily in surface-exposed cryst. areas of the cellulosic substrate. Using time-resolved in situ at. force microscopy (AFM), the authors further demonstrated that cellulose nanofibrils exposed on the surface were degraded into shorter and thinner insol. fragments. Also using AFM, the authors showed that prior action of LPMO enabled cellulases to attack otherwise highly resistant cryst. substrate areas and that it promoted an overall faster and more complete surface degrdn. Overall, this study reveals key characteristics of LPMO action on the cellulose surface and suggests the effects of substrate morphol. on the synergy between LPMO and hydrolytic enzymes in cellulose depolymn.
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53. 53
  Siqueira, P.; Siqueira, É.; De Lima, A. E.; Siqueira, G.; Pinzón-Garcia, A. D.; Lopes, A. P.; Segura, M. E. C.; Isaac, A.; Pereira, F. V.; Botaro, V. R. Three-dimensional stable alginate-nanocellulose gels for biomedical applications: towards tunable mechanical properties and cell growing. Nanomaterials 2019, 9, 78, DOI: 10.3390/nano9010078
  53
  Three-dimensional stable alginate-nanocellulose gels for biomedical applications: towards tunable mechanical properties and cell growing
  Siqueira, Priscila; Siqueira, Eder; de Lima, Ana Elza; Siqueira, Gilberto; Pinzon-Garcia, Ana Delia; Lopes, Ana Paula; Segura, Maria Esperanza Cortes; Isaac, Augusta; Pereira, Fabiano Vargas; Botaro, Vagner Roberto
  Nanomaterials (2019), 9 (1), 78/1-78/22CODEN: NANOKO; ISSN:2079-4991. (MDPI AG)
  Hydrogels have been studied as promising materials in different biomedical applications such as cell culture in tissue engineering or in wound healing. In this work, we synthesized different nanocellulose-alginate hydrogels contg. cellulose nanocrystals, TEMPO-oxidized cellulose nanocrystals (CNCTs), cellulose nanofibers or TEMPO-oxidized cellulose nanofibers (CNFTs). The hydrogels were freeze-dried and named as gels. The nanocelluloses and the gels were characterized by different techniques such as Fourier-transform IR spectroscopy (FTIR), SEM (SEM), transmission electron microscopy (TEM), thermogravimetric anal. (TGA), and dynamic mech. thermal anal. (DMTA), while the biol. features were characterized by cytotoxicity and cell growth assays. The addn. of CNCTs or CNFTs in alginate gels contributed to the formation of porous structure (diam. of pores in the range between 40 and 150μm). TEMPO-oxidized cellulose nanofibers have proven to play a crucial role in improving the dimensional stability of the samples when compared to the pure alginate gels, mainly after a thermal post-treatment of these gels contg. 50 wt of CNFT, which significantly increased the Ca2+ crosslinking d. in the gel structure. The morphol. characteristics, the mech. properties, and the non-cytotoxic behavior of the CNFT-alginate gels improved bioadhesion, growth, and proliferation of the cells onto the gels. Thus, the alginate-nanocellulose gels might find applications in tissue engineering field, as for instance, in tissue repair or wound healing applications.
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54. 54
  Xie, K.; Yu, Y.; Shi, Y. Synthesis and characterization of cellulose/silica hybrid materials with chemical crosslinking. Carbohydr. Polym. 2009, 78, 799– 805, DOI: 10.1016/j.carbpol.2009.06.019
  54
  Synthesis and characterization of cellulose/silica hybrid materials with chemical crosslinking
  Xie, Kongliang; Yu, Yanhong; Shi, Yaqi
  Carbohydrate Polymers (2009), 78 (4), 799-805CODEN: CAPOD8; ISSN:0144-8617. (Elsevier Ltd.)
  The cellulose/silica hybrid biomaterials are prepd. by sol-gel covalent crosslinking process. The tetraethoxysilane (TEOS) as precursor, γ-aminopropyltriethoxylsilane (APTES) as couple agent, and 2,4,6-tri[(2-epihydrin-3-bimethyl-ammonium)propyl]-1,3,5-triazine chloride (Tri-EBAC) as crosslinking agent, are used in the sol-gel crosslinking process. The chem. and morphol. structures of cellulose/silica covalent crosslinking hybrids are investigated with micro-FT-IR spectra, nitrogen element anal., X-ray diffraction, SEM, AFM, and DSC. The results show that the cellulose/silica hybrids form new macromol. structures. In sol-gel process, inorg. particles are dispersed at the nanometer scale in the cellulose host matrix, bounding to the cellulose through covalent bonds. The cellulose/silica covalent crosslinking hybrid can form good and smooth film on the cellulose. The thermal properties of org./inorg. hybrids are improved.
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55. 55
  Bhattacharjee, S. DLS and zeta potential - What they are and what they are not?. J. Controlled Release 2016, 235, 337– 351, DOI: 10.1016/j.jconrel.2016.06.017
  55
  DLS and zeta potential - What they are and what they are not?
  Bhattacharjee, Sourav
  Journal of Controlled Release (2016), 235 (), 337-351CODEN: JCREEC; ISSN:0168-3659. (Elsevier B.V.)
  A review. Adequate characterization of NPs (nanoparticles) is of paramount importance to develop well defined nanoformulations of therapeutic relevance. Detn. of particle size and surface charge of NPs are indispensable for proper characterization of NPs. DLS (dynamic light scattering) and ZP (zeta potential) measurements have gained popularity as simple, easy and reproducible tools to ascertain particle size and surface charge. Unfortunately, on practical grounds plenty of challenges exist regarding these two techniques including inadequate understanding of the operating principles and dealing with crit. issues like sample prepn. and interpretation of the data. As both DLS and ZP have emerged from the realms of phys. colloid chem. - it is difficult for researchers engaged in nanomedicine research to master these two techniques. Addnl., there is little literature available in drug delivery research which offers a simple, concise account on these techniques. This review tries to address this issue while providing the fundamental principles of these techniques, summarizing the core math. principles and offering practical guidelines on tackling commonly encountered problems while running DLS and ZP measurements. Finally, the review tries to analyze the relevance of these two techniques from translatory perspective.
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56. 56
  Johnston, L. J.; Jakubek, Z. J.; Beck, S.; Araki, J.; Cranston, E. D.; Danumah, C.; Fox, D.; Li, H.; Wang, J.; Mester, Z.; Moores, A.; Rabb, S. A.; Murphy, K. E.; Stephan, C. Determination of sulfur and sulfate half-ester content in cellulose nanocrystals: an interlaboratory comparison. Metrologia 2018, 55, 872, DOI: 10.1088/1681-7575/aaeb60
  56
  Determination of sulfur and sulfate half-ester content in cellulose nanocrystals: an interlaboratory comparison
  Johnston, Linda J.; Jakubek, Zygmunt J.; Beck, Stephanie; Araki, Jun; Cranston, Emily D.; Danumah, Christophe; Fox, Douglas; Li, Haifeng; Wang, Jun; Mester, Zoltan; Moores, Audrey; Murphy, Karen; Rabb, Savelas A.; Rudie, Alan; Stephan, Chady
  Metrologia (2018), 55 (6), 872-882CODEN: MTRGAU; ISSN:1681-7575. (IOP Publishing Ltd.)
  Charged functional groups on the surface of cellulose nanocrystals (CNCs) are important for controlling the colloidal stability of suspensions and the interaction of the material with its environment. Quantification of surface groups is therefore an important metric for reproducible prodn. of this nanomaterial. Here we report the results of an inter lab. comparison (ILC) with twelve participants piloted by National Research Council Canada (NRC) that evaluated two methods for detg. the sulfur content for an NRC ref. material (CNCD-1) produced from CNCs extd. by sulfuric acid hydrolysis of wood pulp. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) was used to measure the total sulfur content of CNCs after microwave assisted digestion in strong acid. Conductometric titrn. quantified the neg. charged sulfate half-ester groups on the CNC surface after dialysis and protonation using ion exchange resin. The data was analyzed with an ASTM method that employs h and k statistics to identify data sets for which the lab. mean or std. deviation show excessive variation from the overall mean or std. deviation and the NIST consensus builder (NICOB) engine using the DerSimonian-Laird meta-anal. to det. a consensus est. of the mean and its assocd. measurement uncertainty. The consensus ests. ± uncertainty for total sulfur and sulfate half ester content were (8771 ± 94) mg kg-1 and (252.0 ± 8.2) mmol kg-1, resp. Neither approach identified any outliers in the data sets and the consensus ests. were in agreement with values obtained during certification of the ref. material. The results confirmed that the difference between the sulfur content measured by conductometric titrn. and ICP-OES is larger than the combined 95% expanded uncertainties. The higher sulfur content measured by ICP-OES may reflect the presence of sulfur impurities that are not detected by titrn. Overall the ILC provides validation for the protocols for the two methods and indicates that both are reasonably tolerant of small variations from the protocol. A more reliable method of assessing the titrn. endpoint and a quality control (QC) sample were identified as potential improvements to reduce variability for the conductometric titrn.
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57. 57
  Bennati-Granier, C.; Garajova, S.; Champion, C.; Grisel, S.; Haon, M.; Zhou, S.; Fanuel, M.; Ropartz, D.; Rogniaux, H.; Gimbert, I.; Record, E.; Berrin, J. G. Substrate specificity and regioselectivity of fungal AA9 lytic polysaccharide monooxygenases secreted by Podospora anserina. Biotechnol. Biofuels 2015, 8, 90, DOI: 10.1186/s13068-015-0274-3
  57
  Substrate specificity and regioselectivity of fungal AA9 lytic polysaccharide monooxygenases secreted by Podospora anserina
  Bennati-Granier Chloe; Garajova Sona; Champion Charlotte; Grisel Sacha; Haon Mireille; Zhou Simeng; Gimbert Isabelle; Record Eric; Berrin Jean-Guy; Bennati-Granier Chloe; Garajova Sona; Champion Charlotte; Grisel Sacha; Haon Mireille; Zhou Simeng; Gimbert Isabelle; Record Eric; Berrin Jean-Guy; Garajova Sona; Fanuel Mathieu; Ropartz David; Rogniaux Helene
  Biotechnology for biofuels (2015), 8 (), 90 ISSN:1754-6834.
  BACKGROUND: The understanding of enzymatic polysaccharide degradation has progressed intensely in the past few years with the identification of a new class of fungal-secreted enzymes, the lytic polysaccharide monooxygenases (LPMOs) that enhance cellulose conversion. In the fungal kingdom, saprotrophic fungi display a high number of genes encoding LPMOs from family AA9 but the functional relevance of this redundancy is not fully understood. RESULTS: In this study, we investigated a set of AA9 LPMOs identified in the secretomes of the coprophilous ascomycete Podospora anserina, a biomass degrader of recalcitrant substrates. Their activity was assayed on cellulose in synergy with the cellobiose dehydrogenase from the same organism. We showed that the total release of oxidized oligosaccharides from cellulose was higher for PaLPMO9A, PaLPMO9E, and PaLPMO9H that harbored a carbohydrate-binding module from the family CBM1. Investigation of their regioselective mode of action revealed that PaLPMO9A and PaLPMO9H oxidatively cleaved at both C1 and C4 positions while PaLPMO9E released only C1-oxidized products. Rapid cleavage of cellulose was observed using PaLPMO9H that was the most versatile in terms of substrate specificity as it also displayed activity on cello-oligosaccharides and β-(1,4)-linked hemicellulose polysaccharides (e.g., xyloglucan, glucomannan). CONCLUSIONS: This study provides insights into the mode of cleavage and substrate specificities of fungal AA9 LPMOs that will facilitate their application for the development of future biorefineries.
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58. 58
  Isogai, A.; Saito, T.; Fukuzumi, H. TEMPO-oxidized cellulose nanofibers. Nanoscale 2011, 3, 71– 85, DOI: 10.1039/C0NR00583E
  58
  TEMPO-oxidized cellulose nanofibers
  Isogai, Akira; Saito, Tsuguyuki; Fukuzumi, Hayaka
  Nanoscale (2011), 3 (1), 71-85CODEN: NANOHL; ISSN:2040-3372. (Royal Society of Chemistry)
  A review on prepn. methods and fundamental characteristics of TEMPO-oxidized cellulose nanofibers (TOCN) and tensile strengths, thermal stability, and oxygen permeability of TOCN/poly(lactic acid) composite.
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59. 59
  Zhang, R.; Liu, Y. High energy oxidation and organosolv solubilization for high yield isolation of cellulose nanocrystals (CNC) from Eucalyptus hardwood. Sci. Rep. 2018, 8, 16505, DOI: 10.1038/s41598-018-34667-2
  59
  High energy oxidation and organosolv solubilization for high yield isolation of cellulose nanocrystals (CNC) from Eucalyptus hardwood
  Zhang Renli; Liu Yun
  Scientific reports (2018), 8 (1), 16505 ISSN:.
  Cellulose nanocrystals (CNC) have been widely used as responsive materials, chiral templates, and tough nano-composites due to its unparalleled properties. Acid and enzyme hydrolyses are extensively employed to prepare CNC. These traditional approaches exhibit inherent limitations of corrosion hazards, time-consuming process, and/or low yield. Herein, irradiation oxidation and organosolv solubilization are conducted to cause rapid degradation with simultaneous crystallization of cellulose to achieve approx. 87% yield of CNC. The morphology, spectroscopic, and stability properties of the as-prepared CNC are characterized through UV-vis spectroscopy, zetal potential, XRD, TEM, DLS, GPC, FT-IR and TGA techniques. The resultant CNC suspension presents unique property with high stability after 9 months storage at 4 °C. Moreover, CNC liquid crystal phase is successfully generated by addition of anions or cations solution to the CNC aqueous dispersion without stirring. The innovative approach in this work opens an avenue to obtain CNC directly from lignocellulosic biomass through irradiation oxidation and organosolv solubilization without acid hydrolysis and washing procedure.
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60. 60
  Oksman, K.; Etang, J. A.; Mathew, A. P.; Jonobi, M. Cellulose nanowhiskers separated from a bio-residue from wood bioethanol production. Biomass Bioenergy 2011, 35, 146– 152, DOI: 10.1016/j.biombioe.2010.08.021
  60
  Cellulose nanowhiskers separated from a bioresidue from wood bioethanol production
  Oksman, Kristiina; Etang, Jackson A.; Mathew, Aji P.; Jonoobi, Mehdi
  Biomass and Bioenergy (2011), 35 (1), 146-152CODEN: BMSBEO; ISSN:0961-9534. (Elsevier Ltd.)
  The aim of this study was to explore the utilization of industrial bioresidues as a source of raw material for the industrial prodn. of cellulose nanowhiskers. The used residue, obtained from a bioethanol pilot plant, was first purified using chem. extn. and bleaching, and then sepd. to nanowhiskers by mech. treatments such as ultrasonication, high-pressure homogenization as well as chem. acid hydrolysis. The chem. compns. and characteristics of the bioresidue were studied before and after the purifn. using a TAPPI std., Fourier-transform IR spectroscopy (FTIR), X-ray diffraction (XRD), and thermogravimetric anal. (TGA). The morphol. of the isolated nanowhiskers was characterized using at. force microscope (AFM). The chem. compn. of the used bioresidue was found to be 49.5% cellulose, 42.1% lignin, and 8.4% extractives. The crystallinity of the bioresidue was 14.5% and it increased to more than 73% after the purifn. process. The nanowhiskers isolated using ultrasonication or high-pressure homogenization had better thermal stability than nanowhiskers isolated with acid hydrolysis. The AFM study showed that a simple ultrasonication and homogenization processes resulted in nanosize whiskers with diams. in the 10-20 nm range.
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61. 61
  Herrera, M. A.; Mathew, A. P.; Oksman, K. Characterization of cellulose nanowhiskers: A comparison of two industrial bioresidues. Iop Conf. Ser.: Mater. Sci. Eng. 2012, 31, 012006 DOI: 10.1088/1757-899X/31/1/012006
  61
  Characterization of cellulose nanowhiskers: a comparison of two industrial bio-residues
  Herrera, M. A.; Mathew, A. P.; Oksman, K.
  IOP Conference Series: Materials Science and Engineering (2012), 31 (), 012006/1-012006/8CODEN: ICSMGW; ISSN:1757-899X. (Institute of Physics Publishing)
  Cellulose nanowhiskers sepd. from two different industrial residues, sludge from cellulose prodn. (CNWSL) and lignin residue from ethanol prodn. (CNWER), were compared in order to evaluate their characteristics and their potential as a source for the prodn. of cellulose nanowhiskers (CNWs). It was found that CNWSL and CNWER suspensions exhibited flow birefringence when they were studied through cross-polarized filters. Transmission electron microscopy (TEM) study showed that the CNWSL were longer (377 nm) than CNWER (301 nm). It was also demonstrated that most CNWSL had nanowhiskers between 375-449 nm and CNWER between 300-374 nm. The UV/Vis spectroscopy showed a stronger interference in the UV and visible region for the CNWSL films. The crystallinity, obtained by X-ray anal., was higher for CNWSL (86%) than for CNWER(78%). Finally, the thermal stability appeared to be slightly higher for the CNWER than for CNWSL. Both studied residues seem to be suitable sources for large-scale prodn. of CNWs.
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62. 62
  Roman, M.; Winter, W. T. Effect of sulfate groups from sulfuric acid hydrolysis on the thermal degradation behavior of bacterial cellulose. Biomacromolecules 2004, 5, 1671– 1677, DOI: 10.1021/bm034519+
  62
  Effect of Sulfate Groups from Sulfuric Acid Hydrolysis on the Thermal Degradation Behavior of Bacterial Cellulose
  Roman, Maren; Winter, William T.
  Biomacromolecules (2004), 5 (5), 1671-1677CODEN: BOMAF6; ISSN:1525-7797. (American Chemical Society)
  When used as fillers in polymer composites, the thermostability of cellulose crystals is important. Sulfate groups, introduced during hydrolysis with sulfuric acid, are suspected to diminish the thermostability. To elucidate the relationship between the hydrolysis conditions, the no. of sulfate groups introduced, and the thermal degrdn. behavior of cellulose crystals, bacterial cellulose was hydrolyzed with sulfuric acid under different hydrolysis conditions. The no. of sulfate groups in the crystals was detd. by potentiometric titrn. The thermal degrdn. behavior was investigated by thermogravimetric anal. The sulfate group content increased with acid concn., acid-to-cellulose ratio, and hydrolysis time. Even at low levels, the sulfate groups caused a significant decrease in degrdn. temps. and an increase in char fraction confirming that the sulfate groups act as flame retardants. Profile anal. of the deriv. thermogravimetric curves indicated thermal sepn. of the degrdn. reactions by the sulfate groups into low- and high-temp. processes. The Broido method was used to det. activation energies for the degrdn. processes. The activation energies were lower at larger amts. of sulfate groups suggesting a catalytic effect on the degrdn. reactions. For high thermostability in the crystals, low acid concns., small acid-to-cellulose ratios, and short hydrolysis times should be used.
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63. 63
  Rosa, M. F.; Medeiros, E. S.; Malmonge, J. A.; Gregorski, K. S.; Wood, D. F.; Mattoso, L. H. C.; Glenn, G.; Orts, W. J.; Imam, S. H. Cellulose nanowhiskers from coconut husk fibers: Effect of preparation conditions on their thermal and morphological behavior. Carbohydr. Polym. 2010, 81, 83– 92, DOI: 10.1016/j.carbpol.2010.01.059
  63
  Cellulose nanowhiskers from coconut husk fibers: Effect of preparation conditions on their thermal and morphological behavior
  Rosa, M. F.; Medeiros, E. S.; Malmonge, J. A.; Gregorski, K. S.; Wood, D. F.; Mattoso, L. H. C.; Glenn, G.; Orts, W. J.; Imam, S. H.
  Carbohydrate Polymers (2010), 81 (1), 83-92CODEN: CAPOD8; ISSN:0144-8617. (Elsevier Ltd.)
  Cellulose nanowhiskers were prepd. by sulfuric acid hydrolysis from coconut husk fibers which had previously been submitted to a delignification process. The effects of prepn. conditions on the thermal and morphol. behavior of the nanocrystals were investigated. Cellulose nanowhisker suspensions were characterized by Fourier transform IR spectroscopy (FTIR), transmission electron microscopy (TEM), thermogravimetric anal. (TGA) and X-ray diffraction. Results showed that it was possible to obtain ultrathin cellulose nanowhiskers with diams. as low as 5 nm and aspect ratio of up to 60. A possible correlation between prepn. conditions and particle size was not obsd. Higher residual lignin content was found to increase thermal stability indicating that by controlling reaction conditions one can tailor the thermal properties of the nanowhiskers.
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64. 64
  Stevens, J. S.; Schroeder, S. L. M. Quantitative analysis of saccharides by X-ray photoelectron spectroscopy. Surf. Interface Anal. 2009, 41, 453– 462, DOI: 10.1002/sia.3047
  64
  Quantitative analysis of saccharides by X-ray photoelectron spectroscopy
  Stevens, Joanna S.; Schroeder, Sven L. M.
  Surface and Interface Analysis (2009), 41 (6), 453-462CODEN: SIANDQ; ISSN:0142-2421. (John Wiley & Sons Ltd.)
  A series of saccharides, including several monohydrates and one amorphous phase, has been investigated by XPS, providing the first database of survey and high-resoln. spectra for this class of compds. Known stoichiometries and XPS-detd. elemental compns. agree well. XPS has sufficient precision for distinguishing the stoichiometries of mono-, di-, and polysaccharides. The C 1s chem. shifts of the acetal and alc. groups are similar for all samples, albeit with slight binding energy increases in the series from monosaccharides to disaccharides and polysaccharides. Increasing X-ray exposure causes a radiation-induced increase of the aliph. hydrocarbon emission at 285 eV, concomitant with the appearance of a high binding energy C 1s emission peak at 289.1 eV and a decrease in the O 1s/C 1s emission intensity ratio. Formation of aliph. hydrocarbon groups is proposed to arise from dehydroxylation, while the increase in the 289.1 eV peak can be attributed to double dehydroxylation at the C1 position or partial oxidn. of an alc. or acetal group. The rate of radiation damage correlates with previously reported rates of thermally induced caramelization.
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65. 65
  Moulder, J.F.; Stickle, W.F.; Sobol, P.E.; Bomben, K.D. Handbook of X-ray Photoelectron Spectroscopy. Physical Electronics 1995, ISBN: 9780964812413
  There is no corresponding record for this reference.
66. 66
  Mathew, A. P.; Oksman, K.; Karim, Z.; Liu, P.; Khan, S. A.; Naseri, N. Process scale up and characterization of wood cellulose nanocrystals hydrolysed using bioethanol pilot plant. Ind. Crops Prod. 2014, 58, 212– 219, DOI: 10.1016/j.indcrop.2014.04.035
  66
  Process scale up and characterization of wood cellulose nanocrystals hydrolysed using bioethanol pilot plant
  Mathew, Aji P.; Oksman, Kristiina; Karim, Zoheb; Liu, Peng; Khan, Saad Ahmed; Naseri, Narges
  Industrial Crops and Products (2014), 58 (), 212-219CODEN: ICRDEW; ISSN:0926-6690. (Elsevier B.V.)
  The paper discusses the isolation of cellulose nanocrystals (CNCBE) from wood resources by integrating the processing with pilot-scale bioethanol processing unit. The nanocrystals were isolated from cellulose obtained by acid pretreatment of in a bioethanol pilot-scale facility, followed by a series of chem. processes and subsequent homogenization using a lab-scale homogenizer. The isolated nanocrystals had diams. of 5-15 nm, cellulose I cryst. structure and formed a thick semi-transparent gel at low concn. (2 wt%). XPS data showed that these nanocrystals had predominantly O=C-O surface groups which also contributed to its high neg. zeta potential. Casted CNCBE films showed excellent mech. performance (200 MPa of strength, 16 GPa of modulus) and transparency and were also found to be cytocompatible. The developed process route resulted in high-quality nanocellulose crystals with a yield of 600 g/day.
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67. 67
  Missoum, K.; Sadocco, P.; Causio, J.; Belgacem, M. N.; Bras, J. Antibacterial activity and biodegradability assessment of chemically grafted nanofibrillated cellulose. Mater. Sci. Eng. C Mater. Biol. Appl. 2014, 45, 477– 483, DOI: 10.1016/j.msec.2014.09.037
  67
  Antibacterial activity and biodegradability assessment of chemically grafted nanofibrillated cellulose
  Missoum, Karim; Sadocco, Patrizia; Causio, Jessica; Belgacem, Mohamed Naceur; Bras, Julien
  Materials Science & Engineering, C: Materials for Biological Applications (2014), 45 (), 477-483CODEN: MSCEEE; ISSN:0928-4931. (Elsevier B.V.)
  Nanofibrillated cellulose (NFC) and their derivs. were prepd. using three chem. surface modification strategies. All grafting was characterized by FTIR and contact angle measurements in order to evaluate the efficiency of grafting. Antibacterial activities of neat and grafted samples were investigated against two kinds of bacteria (i.e. Gram + (Staphylococcus aureus) and Gram - (Klebsiella pneumoniae)). All the grafted samples displayed promising results with at least bacteriostatic effect or bactericidal properties. They also strongly enhanced the photo-catalytic antimicrobial effect of TiO2. This study proves that it is better to use grafted NFC either alone or for functionalization with TiO2 if anti-bacterial properties are desired. The cellulose backbone is known to be easily biodegradable in different biodegrdn. conditions and environments. The chem. surface modifications applied on NFC in the present work did not neg. influence this valuable property of cellulose but help for monitoring this property, which could be very useful for paper, packaging and composites.
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68. 68
  Tavakolian, M.; Okshevsky, M.; van de Ven, T. G. M.; Tufenkji, N. Developing antibacterial nanocrystalline cellulose using natural antibacterial agents. ACS Appl. Mater. Interfaces 2018, 10, 33827– 33838, DOI: 10.1021/acsami.8b08770
  68
  Developing Antibacterial Nanocrystalline Cellulose Using Natural Antibacterial Agents
  Tavakolian, Mandana; Okshevsky, Mira; van de Ven, Theo G. M.; Tufenkji, Nathalie
  ACS Applied Materials & Interfaces (2018), 10 (40), 33827-33838CODEN: AAMICK; ISSN:1944-8244. (American Chemical Society)
  We used hairy nanocryst. cellulose functionalized with aldehyde groups, otherwise known as sterically stabilized nanocryst. cellulose (SNCC), to facilitate the attachment of the antibacterial agents lysozyme and nisin. Immobilization was achieved using a simple, green process that does not require any linker or activator. XPS and Fourier transform IR spectroscopy analyses showed successful attachment of both nisin and lysozyme onto the SNCC. The efficacy of the conjugated nanocellulose against the model bacteria Bacillus subtilis and Staphylococcus aureus was tested in terms of bacterial growth, cell viability, and biofilm formation/removal. The results show that the min. inhibitory concn. of the conjugated nanocellulose is higher than that of lysozyme and nisin in free form, which was expected given that immobilization reduces the possible spatial orientations of these proteins. We obsd. that free nisin is not active against S. aureus after 24 h of exposure due to either deactivation of free nisin or development of resistance in S. aureus against free nisin. Interestingly, we did not observe this phenomenon when the bacteria were exposed to antibacterials immobilized on nanocellulose, suggesting that immobilization of antibacterial agents onto SNCC effectively retains their activity over long time periods. We suggest that antibacterial SNCC is a promising candidate for the development of antibacterial wound dressings.
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69. 69
  Vytrasova, J.; Tylsova, A.; Brozkova, I.; Cervenka, L.; Pejchalova, M.; Havelka, P. Antimicrobial effect of oxidized cellulose salts. J. Ind. Microbiol. Biotechnol. 2008, 35, 1247– 1252, DOI: 10.1007/s10295-008-0421-y
  69
  Antimicrobial effect of oxidized cellulose salts
  Vytrasova, Jarmila; Tylsova, Andrea; Brozkova, Iveta; Cervenka, Libor; Pejchalova, Marcela; Havelka, Pavel
  Journal of Industrial Microbiology & Biotechnology (2008), 35 (11), 1247-1252CODEN: JIMBFL; ISSN:1367-5435. (Springer)
  Antimicrobial properties of oxidized cellulose and its salts in linters (-L) and microsphere (-M) form (OKCEL H-L, OKCEL Zn-M, OKCEL ZnNa-L, OKCEL ZnNa-M and OKCEL Ag-L) were tested by a diln. method against a spectrum of microbial strains: Escherichia coli, Pseudomonas aeruginosa, Staphylococcus epidermidis, Bacillus licheniformis, Aspergillus niger, Penicillium chrysogenum, Rhizopus oryzae, Scopulariopsis brevicaulis, Candida albicans and Candida tropicalis. OKCEL Ag-L exhibited antimicrobial activity in the range 0.1-3.5% w/v against all the bacteria and fungi involved in this study. Strong inhibition by OKCEL ZnNa-M was obsd. for Staphylococcus epidermidis, Bacillus licheniformis, Rhizopus oryzae, Candida albicans and Candida tropicalis in the range 0.5-2.0% w/v. Antimicrobial effects of oxidized cellulose and its salts in textile form were investigated by a diffusion and diln. method against the spectrum of above-cited microbial strains extended by Clostridium perfringens. Generally, OKCEL Ag-T, OKCEL Zn-T and OKCEL H-T showed high antimicrobial activity against populations of Pseudomonas aeruginosa, Bacillus licheniformis and Staphylococcus epidermidis. OKCEL Zn-T was the only sample suppressing the growth of species.
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70. 70
  Abaev, I. K.; Kaputskiĭ, V. E.; Adarchenko, A. A.; Sobeshchukh, O. P. Mechanism of the antibacterial action of monocarboxycellulose and other ion-exchange derivatives of cellulose. Antibiot. Med. Biotekhnol. 1986, 31, 624– 628
  70
  Mechanism of antibacterial effects of monocarboxylcellulose and other ion-exchange derivatives of cellulose
  Abaev, Yu. K.; Kaputskii, V. E.; Adarchenko, A. A.; Sobeshchuk, O. P.
  Antibiotiki i Meditsinskaya Biotekhnologiya (1986), 31 (8), 624-8CODEN: AMBIEH; ISSN:0233-7525.
  The mechanism of the antibacterial effect of monocarboxylcellulose (MCC) and other ion-exchange derivs. of cellulose was studied. MCC, cellulose phosphate, and aminocellulose had a pronounced antibacterial effect due to the presence of the ionic group H+ or OH-. A role in this process was played by sorption. The level of the antibacterial activity of MCC depended on the no. of the carboxyl groups. MCC is promising as a dressing material.
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71. 71
  Saini, S.; Falco, Ç. Y.; Belgacem, M. N.; Bras, J. Surface cationized cellulose nanofibrils for the production of contact active antimicrobial surfaces. Carbohydr. Polym. 2016, 135, 239– 247, DOI: 10.1016/j.carbpol.2015.09.002
  71
  Surface cationized cellulose nanofibrils for the production of contact active antimicrobial surfaces
  Saini, Seema; Yucel Falco, Cigdem; Belgacem, Mohamed Naceur; Bras, Julien
  Carbohydrate Polymers (2016), 135 (), 239-247CODEN: CAPOD8; ISSN:0144-8617. (Elsevier Ltd.)
  In the last decade, a new fiber pretreatment has been proposed to make easy cellulose fibrillation into microfibrils. In this context, different surface cationized MFC was prepd. by optimizing the exptl. parameters for cellulose fibers pretreatment before fibrillation. All MFCs were characterized by conductometric titrn. to establish degree of substitution, field emission gun SEM (FEG-SEM), at. force microscopy (AFM) and optical microscopy assessed the effect of pretreatment on the morphol. of the ensuing MFCs. Antibacterial activities of neat and cationized MFC samples were investigated against Gram pos. bacteria (Bacillus subtilis, Staphylococcus aureus) and Gram neg. bacteria (Escherichia coli). The CATMFC sample at DS greater than 0.18 displayed promising results with antibacterial properties without any leaching of quaternary ammonium into the environment. This work proved the potential of cationic MFCs with specific DS for contact active antimicrobial surface applications in active food packaging, medical packaging or in health and cosmetic field.
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72. 72
  Breijyeh, Z.; Jubeh, B.; Karaman, R. Resistance of Gram-negative bacteria to current antibacterial agents and approaches to resolve it. Molecules 2020, 25, 1340, DOI: 10.3390/molecules25061340
  72
  Resistance of gram-negative bacteria to current antibacterial agents and approaches to resolve it
  Breijyeh, Zeinab; Jubeh, Buthaina; Karaman, Rafik
  Molecules (2020), 25 (6), 1340CODEN: MOLEFW; ISSN:1420-3049. (MDPI AG)
  Antimicrobial resistance represents an enormous global health crisis and one of the most serious threats humans face today. Some bacterial strains have acquired resistance to nearly all antibiotics. Therefore, new antibacterial agents are crucially needed to overcome resistant bacteria. In 2017, the World Health Organization (WHO) has published a list of antibiotic-resistant priority pathogens, pathogens which present a great threat to humans and to which new antibiotics are urgently needed the list is categorized according to the urgency of need for new antibiotics as crit., high, and medium priority, in order to guide and promote research and development of new antibiotics. The majority of the WHO list is Gram-neg. bacterial pathogens. Due to their distinctive structure, Gram-neg. bacteria are more resistant than Gram-pos. bacteria, and cause significant morbidity and mortality worldwide. Several strategies have been reported to fight and control resistant Gram-neg. bacteria, like the development of antimicrobial auxiliary agents, structural modification of existing antibiotics, and research into and the study of chem. structures with new mechanisms of action and novel targets that resistant bacteria are sensitive to. Research efforts have been made to meet the urgent need for new treatments; some have succeeded to yield activity against resistant Gram-neg. bacteria by deactivating the mechanism of resistance, like the action of the β-lactamase Inhibitor antibiotic adjuvants. Another promising trend was by referring to nature to develop naturally derived agents with antibacterial activity on novel targets, agents such as bacteriophages, DCAP(2-((3-(3,6-dichloro-9H-carbazol-9-yl)-2-hydroxypropyl)amino)-2(hydroxymethyl)propane1,3- diol, Odilorhabdins (ODLs), peptidic benzimidazoles, quorum sensing (QS) inhibitors, and metal-based antibacterial agents.
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73. 73
  Herbaud, M. L.; Guiseppi, A.; Denizot, F.; Haiech, J.; Kilhoffer, M. C. Calcium signalling in Bacillus subtilis. Biochim. Biophys. Acta 1998, 1448, 212– 226, DOI: 10.1016/s0167-4889(98)00145-1
  73
  Calcium signalling in Bacillus subtilis
  Herbaud, Marie-Laure; Guiseppi, Annick; Denizot, Francois; Haiech, Jacques; Kilhoffer, Marie-Claude
  Biochimica et Biophysica Acta, Molecular Cell Research (1998), 1448 (2), 212-226CODEN: BBAMCO; ISSN:0167-4889. (Elsevier B.V.)
  Few systematic studies have been devoted to investigating the role of Ca2+ as an intracellular messenger in prokaryotes. Here we report an investigation on the potential involvement of Ca2+ in signalling in Bacillus subtilis, a Gram-pos. bacterium. Using aequorin, it is shown that B. subtilis cells tightly regulate intracellular Ca2+ levels. This homeostasis can be changed by an external stimulus such as hydrogen peroxide, pointing to a relationship between oxidative stress and Ca2+ signalling. Also, B. subtilis growth appears to be intimately linked to the presence of Ca2+, as normal growth can be immediately restored by adding Ca2+ to an almost non-growing culture in EGTA contg. Luria broth medium. Addn. of Fe2+ or Mn2+ also restores growth, but with 5-6 h delay, whereas Mg2+ did not have any effect. In addn., the expression of alkyl hydroperoxide reductase C (AhpC), which is strongly enhanced in bacteria grown in the presence of EGTA, also appears to be regulated by Ca2+. Finally, using 45Ca2+ overlay on membrane electrotransferred two-dimensional gels of B. subtilis, four putative Ca2+ binding proteins were found, including AhpC. Our results provide strong evidence for a regulatory role for Ca2+ in bacterial cells.
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74. 74
  Onoda, T.; Enokizono, J.; Kaya, H.; Oshima, A.; Freestone, P.; Norris, V. Effects of calcium and calcium chelators on growth and morphology of Escherichia coli L-form NC-7. J. Bacteriol. 2000, 182, 1419– 1422, DOI: 10.1128/jb.182.5.1419-1422.2000
  74
  Effects of calcium and calcium chelators on growth and morphology of Escherichia coli L-form NC-7
  Onoda, T.; Enokizono, J.; Kaya, H.; Oshima, A.; Freestone, P.; Norris, V.
  Journal of Bacteriology (2000), 182 (5), 1419-1422CODEN: JOBAAY; ISSN:0021-9193. (American Society for Microbiology)
  Growth of a wall-less, L-form of Escherichia coli specifically requires calcium, and in its absence, cells ceased dividing, became spherical, swelled, developed large vacuoles, and eventually lysed. The key cell division protein, FtsZ, was present in the L-form at a concn. five times less than that in the parental strain. One interpretation of these results is that the L-form possesses an enzoskeleton partly regulated by calcium.
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75. 75
  Valenzuela, S. V.; Valls, C.; Schink, V.; Sánchez, D.; Blanca Roncero, M.; Diaz, P.; Martinez, J.; Javier Pastor, F. I. Differential activity of lytic polysaccharide monooxygenases on celluloses of different crystallinity. Effectiveness in the sustainable production of cellulose nanofibrils. Carbohydr. Polym. 2019, 207, 59– 67, DOI: 10.1016/j.carbpol.2018.11.076
  75
  Differential activity of lytic polysaccharide monooxygenases on celluloses of different crystallinity. Effectiveness in the sustainable production of cellulose nanofibrils
  Valenzuela, Susana V.; Valls, Cristina; Schink, Viviane; Sanchez, Daniel; Roncero, M. Blanca; Diaz, Pilar; Martinez, Josefina; Pastor, F. I. Javier
  Carbohydrate Polymers (2019), 207 (), 59-67CODEN: CAPOD8; ISSN:0144-8617. (Elsevier Ltd.)
  A series of cellulosic substrates has been produced, treated with lytic polysaccharide monooxygenase (LPMO) from Streptomyces ambofaciens (SamLPMO10C), and analyzed by high performance anion exchange chromatog. (HPAEC) with pulsed amperometric detection (PAD). The activity of the bacterial LPMO showed high variability depending on the origin and degree of crystallinity of the substrate. Addnl., we tested the effectiveness of SamLPMO10C in the nanofibrillation of flax, a high cryst. agricultural fiber, as a single pretreatment or in combination with cellulases. All pretreatments were followed by a mech. defibrillation by high-pressure homogenization (HPH) to obtain cellulose nanofibrils (NFC). The combined LPMO-cellulase treatment showed higher fibrillation yield, optical transmittance and carboxylate content than control reactions. Therefore, it could be explored as a promising green alternative to reduce the energy consumption in the prodn. of NFC. To our knowledge, this is the first study reporting the effect of a bacterial LPMO in nanocellulose prodn.
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Supporting Information
Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acssuschemeng.0c05036.
- Mass spectrometry data of degradation products generated by MtLPMO, SEM figures, XPS spectra, relative amount of the molecular species, and particle length data for TNCs isolated following different treatments (PDF)
- sc0c05036_si_001.pdf (1.3 MB)
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Lytic Polysaccharide Monooxygenase-Assisted Preparation of Oxidized-Cellulose Nanocrystals with a High Carboxyl Content from the Tunic of Marine Invertebrate Ciona intestinalisClick to copy article linkArticle link copied!

ACS Sustainable Chemistry & Engineering

Abstract

Synopsis

Introduction

Experimental Section

Preparation of the Tunic Material

OS Pretreatment of Tunic

Enzymatic Treatment of Tunic and Analysis of the Product Profile

Isolation of TNCs

LPMO Post-treatment of TNCs

Characterization of TNCs

Morphology and Size

Thermal Analysis

X-ray Photoelectron Spectroscopy (XPS) Analysis

X-ray Diffraction (XRD) Analysis

Evaluation of the TNC Effect on Bacterial Growth

Results and Discussion

Pretreatment Steps for the Preparation of TNCs

Figure 1

Figure 2

Isolation, Recovery, and Properties of Isolated TNCs after Pretreatment

DLS Measurements and Determination of ζ-Potential

Atomic Force Microscopy (AFM) Imaging and Measurement of the TNC Diameter

Figure 3

Thermal Stability of TNCs

Figure 4

Determination of the CrI

XPS Analysis and Determination of the Carboxyl Content of TNCs

Figure 5

Evaluation of the TNC Effect on Bacterial Growth

Figure 6

LPMO Post-treatment of TNCs to Increase the Carboxyl Content

Figure 7

Conclusions

Supporting Information

Terms & Conditions

Author Information

Acknowledgments

Abbreviations

References

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ACS Sustainable Chemistry & Engineering

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Abstract

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References

Supporting Information

Supporting Information

Terms & Conditions

Lytic Polysaccharide Monooxygenase-Assisted Preparation of Oxidized-Cellulose Nanocrystals with a High Carboxyl Content from the Tunic of Marine Invertebrate Ciona intestinalis
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