Monday, May 4, 2009
5-95
Synergistic enhancement of enzymatic hydrolysis of sugar cane bagasse by Trichoderma and Aspergillus cellulases and xilanases enzyme pools
Biomass enzyme blends produced by Trichoderma reesei RUT C30 and a selected strain of Aspergillus awamori, a high β-glucosidase producer, were pooled and the assessed to hydrolyze sugarcane bagasse, industrially treated with steam to be used as cattle feed. The culture supernatants were individually concentrated by ultrafiltration and blended to obtain preparations with different profiles of exo- and endoglucanases, β-glucosidase, xylanases and feruloyl esterase. Hydrolysis experiments were performed with 25 g/L substrate at 50°C, pH 5,0 and 200 rpm for 72 hours. Glucose, cellobiose and xilose were measured by HPLC. In all T. reesei and A. awamori enzymes mixtures it was observed a synergistic enhancement of filter paper activity (FPA) that improved hydrolysis yield around 30%. Hydrolysis experiments using different FPA/g of substrate (5, 10, 15 and 20 FPA/g) resulted on a sharp increase on glucose concentration up to 10 FPA/g that leveled off from 10 to 20 FPA/g of steam treated bagasse. Glucose concentrations of 7,5 g/L, in 72 hours experiments, corresponded to 65% cellulose hydrolysis yield. The sugars syrup presented 1g/L xylose, indicating the presence of a substantial hemicelulose amount in the steam pretreated material. A sharp increase in glucose and xilose concentration was observed for all enzyme loads up to 6 hours of hydrolysis. It was not observed accumulation of cellobiose (inhibitory sugar) throughout the hydrolysis experiments that presented a β-glucosidase/FPA ratio of 5. The feruloyl esterase activity produced by Aspergillus (7 UI/L) seemed to increase the effectiveness of the enzymatic hydrolysis of the studied substrate.
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