Monday, May 4, 2009
12-22
Enzymes Loading Optimization in the Hydrolysis of Sugarcane Bagasse – A Comparison between Bagasse Pretreatment with Lime and Alkaline Hydrogen Peroxide
Sugarcane bagasse is one of the potential lignocellulosic feedstocks for bioethanol production. The ethanol yield depends on the efficiency of conversion of glucans and xylans to fermentable sugars without generating byproducts that are toxic to fermentative microorganisms. Thus, the rate and extent of enzymatic hydrolysis of lignocellulosic biomass is very important and highly dependent on enzyme loadings, hydrolysis periods, and structural features resulting from pretreatments. In this work, the optimization of enzymes loading in the hydrolysis of sugarcane bagasse pretreated using two different agents (lime and alkaline hydrogen peroxide) was performed. The effect of enzymes loading in the fermentable sugars yield was studied through analyses using central composite design (response surface) to determine the optimal loadings of cellulase and b-glucosidase. The responses evaluated were glucose and xylose yield released from pretreated bagasse after enzymatic hydrolysis. Experiments were performed using bagasse as it comes from an alcohol/sugar factory, pretreated with lime and alkaline hydrogen peroxide in previously optimized conditions. The higher hydrolysis yield for bagasse pretreated with lime was found using 66.5 FPU/g dry pretreated biomass of cellulase and 25 CBU/g of dry pretreated biomass of beta-glucosidase. Yields were of 78.6% glucose and 100.0% xylose. For the pretreatment with alkaline hydrogen peroxide, the best result was using 12.7 FPU/g dry pretreated biomass and 7.3 CBU/g of dry pretreated biomass for cellulase and beta-glucosidase, respectively, with yields of 100.0% glucose and 52.6% xylose. The influence of pretreatment on hydrolysis yield and on the enzymes loading necessary for optimal performance were discussed.
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