Differences between Lignin in Unprocessed Wood, Milled Wood, Mutant Wood, and Extracted Lignin Detected by 13C Solid-State NMR

Jingdong Mao,† Kevin M. Holtman,‡ Jay T. Scott,§ John F. Kadla,# and Klaus Schmidt-Rohr*†
Department of Chemistry, Iowa State University, Ames, Iowa 50011; PWA, WRRC, BCE, Agricultural Research Service, U.S. Department of Agriculture, 800 Buchanan Street, Albany, California 94710; Department of Wood and Paper Science, North Carolina State University, Raleigh, North Carolina 27695; and University of British Columbia, 4034-2424 Main Mall, Vancouver, British Columbia V6T1Z4, Canada
J. Agric. Food Chem., 2006, 54 (26), pp 9677–9686
DOI: 10.1021/jf062199q
Publication Date (Web): December 10, 2006
Copyright © 2006 American Chemical Society
†

 Iowa State University.

,
‡

 U.S. Department of Agriculture.

,
§

 North Carolina State University.

,
#

 University of British Columbia.

,
*

 Corresponding author [telephone (515) 294-6105; fax (515) 294-0105; e-mail srohr@iastate.edu].

Abstract

Solid-state 13C nuclear magnetic resonance (NMR) spectroscopy was applied to intact and isolated loblolly pine wood samples to identify potential structural changes induced by tree age, milling, lignin extraction, or naturally occurring mutations. Special attention was paid to ketone and aldehyde as well as nonpolar alkyl groups, which could be observed at low concentrations (<2 in 1000 C) using improved spinning-sideband suppression with gated decoupling. Carbonyl structures were present in intact wood, and there are more keto groups than aldehydes. Their concentrations increased from juvenile to mature wood and with milling time, whereas extraction did not alter the CO fraction. Significant amounts of aldehyde and dihydroconiferyl alcohol residues were present in coniferyl aldehyde dehydrogenase-deficient wood, confirming solution-state NMR spectra of the corresponding lignin. These results demonstrate the utility of solid-state NMR as an assay for changes in the lignin structure of genetically modified plants.

Keywords: Lignin; lignin in wood; lignin isolation; milled wood lignin (MWL); solid-state NMR; spectral editing

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History

  • Published In Issue December 27, 2006
  • Received for review July 31, 2006. Revised manuscript received October 26, 2006. Accepted October 26, 2006. This work was supported by the National Science Foundation under Grant CHE-0138117.

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