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Research Article

Effects of Porous Polystyrene Resin Parameters on Candida antarctica Lipase B Adsorption, Distribution, and Polyester Synthesis Activity

Bo Chen,^† M. Elizabeth Miller,^‡ and Richard A. Gross*^†

NSF I/UCRC for Biocatalysis and Bioprocessing of Macromolecules, Polytechnic University, 6 Metrotech Center, Brooklyn, New York 11201, and Rohm and Haas Co., P.O. Box 904, Spring House, Pennsylvania 19477

Langmuir, 2007, 23 (11), pp 6467–6474

DOI: 10.1021/la063515y

Publication Date (Web): April 24, 2007

†

Polytechnic University.

‡

Rohm and Haas Co.

To whom correspondence should be addressed. Telephone: 718-260-3024. Fax: 718-260-3075. E-mail: rgross@poly.edu.

Abstract

Polystyrene resins with varied particle sizes (35 to 350−600 μm) and pore diameters (300−1000 Å) were employed to study the effects of immobilization resin particle size and pore diameter on Candida antarctica Lipase B (CALB) loading, distribution within resins, fraction of active sites, and catalytic properties for polyester synthesis. CALB adsorbed rapidly (saturation time ≤ 4 min) for particle sizes ≤ 120 μm (pore size = 300 Å). Infrared microspectroscopy showed that CALB forms protein loading fronts regardless of resin particle size at similar enzyme loadings (8%). From the IR images, the fractions of total surface area available to the enzyme are 21, 33, 35, 37, and 88% for particle sizes 350−600, 120, 75, 35 μm (pore size 300 Å), and 35 μm (pore size 1000 Å), respectively. Titration with methyl p-nitrophenyl n-hexylphosphate (MNPHP) showed that the fraction of active CALB molecules adsorbed onto resins was 60%. The fraction of active CALB molecules was invariable as a function of resin particle and pore size. At 8% (w/w) CALB loading, by increasing the immobilization support pore diameter from 300 to 1000 Å, the turnover frequency (TOF) of ε-caprolactone (ε-CL) to polyester increased from 12.4 to 28.2 s^-1. However, the ε-CL conversion rate was not influenced by changes in resin particle size. Similar trends were observed for condensation polymerizations between 1,8-octanediol and adipic acid. The results herein are compared to those obtained with a similar series of methyl methacrylate resins, where variations in particle size largely affected CALB distribution within resins and catalyst activity for polyester synthesis.