Fundamental study of structural features affecting enzymatic hydrolysis of lignocellulosic biomass

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Title: Fundamental study of structural features affecting enzymatic hydrolysis of lignocellulosic biomass
Author: Zhu, Li
Abstract: Lignocellulose is a promising and valuable alternative energy source . Native lignocellulosic biomass has limited accessibility to cellulase enzyme due to structural features ; therefore , pretreatment is an essential prerequisite to make biomass accessible and reactive by altering its structural features . The effects of substrate concentration , addition of cellobiase , enzyme loading , and structural features on biomass digestibility were explored . The addition of supplemental cellobiase to the enzyme complex greatly increased the initial rate and ultimate extent of biomass hydrolysis by converting the strong inhibitor , cellobiose , to glucose . A low substrate concentration (10 g /L ) was employed to prevent end -product inhibition by cellobiose and glucose . The rate and extent of biomass hydrolysis significantly depend on enzyme loading and structural features resulting from pretreatment , thus the hydrolysis and pretreatment processes are intimately coupled because of structural features . Model lignocelluloses with various structural features were hydrolyzed with a variety of cellulase loadings for 1 , 6 , and 72 h . Glucan , xylan , and total sugar conversions at 1 , 6 , and 72 h were linearly proportional to the logarithm of cellulase loadings from approximately 10 % to 90 % conversion , indicating that the simplified HCH -1 model is valid for predicting lignocellulose digestibility . Carbohydrate conversions at a given time versus the natural logarithm of cellulase loadings were plotted to obtain the slopes and intercepts which were correlated to structural features (lignin content , acetyl content , cellulose crystallinity , and carbohydrate content ) by both parametric and nonparametric regression models . The predictive ability of the models was evaluated by a variety of biomass (corn stover , bagasse , and rice straw ) treated with lime , dilute acid , ammonia fiber explosion (AFEX ) , and aqueous ammonia . The measured slopes , intercepts , and carbohydrate conversions at 1 , 6 , and 72 h were compared to the values predicted by the parametric and nonparametric models . The smaller mean square error (MSE ) in the parametric models indicates more satisfactorily predictive ability than the nonparametric models . The agreement between the measured and predicted values shows that lignin content , acetyl content , and cellulose crystallinity are key factors that determine biomass digestibility , and that biomass digestibility can be predicted over a wide range of cellulase loadings using the simplified HCH -1 model .
URI: http : / /hdl .handle .net /1969 .1 /4314
Date: 2006-10-30


Fundamental study of structural features affecting enzymatic hydrolysis of lignocellulosic biomass. Available electronically from http : / /hdl .handle .net /1969 .1 /4314 .

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