Tuesday, April 20, 2010
8-26

The characterization and possible role of lignin from steam and organosolv pretreated substrates on enzymatic hydrolysis

Seiji Nakagame, Richard P. Chandra, John F. Kadla, and Jack N. Saddler. Wood Science, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada

During the enzymatic saccharification of pretreated lignocellulosics, one of the most influential substrate components affecting the ease of cellulolytic hydrolysis is lignin. Lignin has been thought to act as both a physical barrier restricting access to cellulose, as well as attracting cellulases resulting in their non-productive binding. To date, the complete removal of lignin from pretreated lignocellulose has been viewed as uneconomical. Therefore, it is inevitable that a pretreated lignocellulosic substrate will contain some amount of lignin. In this study, to gain a fundamental understanding of the effects of substrate lignin on the ease of hydrolysis and the tendency to adsorb cellulases, a comparative analysis of lignin from steam and organosolv pretreated substrates from softwood (lodgepole pine/LPP), hardwood (poplar), and an agricultural residue (corn stover) were prepared with subsequent isolation of lignin via two methods (protease treatment and dioxane extraction). It was found that the type of pretreated substrates affected lignin yields and that the lowest yield was obtained from corn stover. This result suggested that the hydrophobicity of lignin from corn stover was lower than those from poplar and LPP. The isolated lignin from LPP and steam pretreated poplar had a negative effect on Avicel hydrolysis, whereas other isolated lignin preparations had little effect. To elucidate the relationship between lignin properties and their inhibitory effects on enzymatic hydrolysis, lignin preparations were characterized using Fourier transform infra-red and nuclear magnetic resonance spectroscopy.

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