(787b) Distinct Effects of Lignin and Xylan On the Enzymatic Hydrolysis of Organosolv Pretreated Biomass

Authors: 
Tu, M., Auburn University


Forestry lignocellulosic biomass is a great potential source of sustainable materials for biofuels and chemicals. Technically, bioconversion process of cellulosic ethanol from forestry feedstock requires pretreatment, enzymatic hydrolysis and fermentation. In order to improve accessibility of lignocellulose to enzymes for hydrolysis, high temperature pretreatment with acid, base or solvent is typically needed to break down the recalcitrant structure of cellulose. Besides the degree of cellulose crystallinity, the interaction between xylan/lignin and cellulase enzymes played a key role in the effective hydrolysis of lignocellulosic biomass. Elucidation of the distinct roles of residual xylan and lignin has been investigated in this study. Loblolly pine (Pinus taeda) and sweetgum (Liquidambar) were pretreated by organosolv and have been quantitatively characterized by the enzymatic hydrolysis based on initial hydrolysis rate and final hydrolysis yield. By correlating the residual lignin and xylan to the initial hydrolysis rate and final yield in organosolv pretreated softwood and hardwood, a more accurate fundamental understanding the roles of xylan and lignin in limiting the enzymatic hydrolysis has been developed. Our results show that Novozyme 22C showed very good performance of hydrolysis on organosolv pretreated biomass. Moreover, the residual xylan in pretreated substrates actually would affect the initial hydrolysis rate much more than that from residual lignin. It suggested that xylan firstly inhibited the cellulase because it’s closer to the cellulose micro-fibril. The lignin residual interacted with cellulase after xylan and decreased the overall hydrolysis yield. The addition of xylanases could increase the initial hydrolysis rate by removing xylan. We also found that in the simultaneous saccharification and fermentation the ethyl xylopyranoside was produced by the enzymatic catalysis of xylose and ethanol.