Monday, April 19, 2010 - 3:00 PM
2-04

Effect of lignin chemical structure on inhibition of enzymatic hydrolysis of cellulose

Hao Liu, State Key Laboratory of Pulp and Paper Engineering, South China Univeristy of Technology, Guangzhou and J. Y. Zhu, USDA Forest Service, Forest Products Laboratory, One Gifford Pinchot Dr, Madison, WI 53726.

Lignin has been recognized as one of the key nonproductive adsorbents of enzymes in cellulose hydrolysis media. Expensive delignification processes have been tried to remove substrate lignin content to reduce enzymatic inhibition. Exogenous protein (BSA) and surfactants have been used as lignin blocking agents to enhance the enzymatic saccharification of cellulose. However, few studies have reported the effect of lignin chemical structure (or functional groups) on enzyme adsorption. The effectiveness of both BSA and surfactants were demonstrated using well washed substrate and their effectiveness on the dissolved lignin in the pretreatment hydrolysate is not yet known. Furthermore, BSA is very expensive which may prohibit its application for commercial processes. Surfactants can cause foaming which negatively impacts simultaneous saccharification and fermentation.

In this presentation we will explore the effect of lignin chemical structure (functional groups) on the inhibition of enzymatic cellulose hydrolysis by using alkaline, organosolv, and sulfonated lignin. These lignins represent the dissolved lignin in the alkaline (including ammonia, ARP, AFEX), organosolv, and SPORL pretreatments. We will also report a novel technique to effectively reduce lignin inhibition (both residual and dissolved lignin) on enzymatic cellulose hydrolysis. Nearly complete elimination of the inhibition of enzymatic cellulose hydrolysis by dissolved and residual lignin is demonstrated using the novel technique.

The present study has significant implications to: (1) Simultaneous Saccharification and Cofermentation (SSCoF) of the cellulose fraction with the hemicelluloses sugar stream (containing dissolved lignin). This cannot currently be done because of the dissolved lignin. And (2) reduced washing of the cellulose fraction (pretreated lignocellulosic solids).


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