Monday, May 4, 2009
5-07
Limiting Factors of Enzymatic Hydrolysis of Lignocellulosic Biomass at High Solids Loadings
Jian Shi1, Mirvat Ebrik1, Bin Yang1, Charles E. Wyman1, and Jiacheng Shen2. (1) Center for Environmental Research and Technology Department of Chemical and Environmental Engineering Bourns College of Engineer, University of California at Riverside, 1084 Columbia Avenue, Riverside, CA 92507, (2) State Key Laboratory of Microbial Technology, Shandong University, 27, Shanda-nan Road, Jinan, China
Cost effective enzymatic hydrolysis is the key for development of economically viable biological processes for lignocellulosic biomass to ethanol conversion. Urgent attention is needed towards an in-depth understanding of the inhibitory mechanisms during enzymatic cellulose digestion especially at low enzyme usage and high solids loadings. This study summarizes our investigations on plausible inhibitory factors such as mixing, pretreatment hydrolysate, and intermediate sugar products that lower the enzymatic digestibility of the water-only and dilute acid pretreated hardwood at 5-100 mg/g glucan plus xylan in raw biomass enzyme loadings and 2-30% solids loadings. Inhibition of enzymatic hydrolysis by pretreatment hydrolysate was examined and washing strategies were evaluated in order to remove detrimental compounds from the preteated solids. A rotating drum with grinding media and roller bottle with baffles were tested at high solid loadings and compared with results from shaker flasks to evaluate the effect of mixing. Combinations of cellulases and beta-glucosidase, xylanase, and beta-xylosidase were employed to identify limiting factors, and enzyme formulations were investigated to maximize total sugar recovery with the lowest possible enzyme loadings. Furthermore, hydrolysis yields and yields of oligosaccharides (cellobiose, low and high DP xylooligomers) were measured over the time course of high solids enzymatic hydrolysis at low and high enzyme loadings. These results provide a better understanding of enzymatic hydrolysis of lignocellulosic biomass and new insights that will facilitate lower cost processes and commercialization of cellulosic ethanol technologies.