Enzymatic hydrolysis of corncob and ethanol production from cellulosic hydrolysate

Enzymatic hydrolysis of corncob and ethanol fermentation from cellulosic hydrolysate were investigated. After corncob was pretreated by 1% H2SO4 at 108 degrees C for 3 h, the cellulosic residue was hydrolyzed by cellulase from Trichoderma reesei ZU-02 and the hydrolysis yield was 67.5%. Poor cellobiase activity in T reesei cellulase restricted the conversion of cellobiose to glucose, and the accumulation of cellobiose caused severe feedback inhibition to the activities of beta-1,4-endoglucanase and beta-1,4-exoglucanase in cellulase system. Supplementing cellobiase from Aspergillus niger ZU-07 greatly reduced the inhibitory effect caused by cellobiose, and the hydrolysis yield was improved to 83.9% with enhanced cellobiase activity of 6.5 CBU g(-1) substrate. fed-batch hydrolysis process was started with a batch hydrolysis containing 100g l(-1) substrate, with cellulosic residue added at 6 and 12h twice to get a final substrate concentration of 200g l(-1). After 60h of reaction, the reducing sugar concentration reached 116.3g l(-1) with a hydrolysis yield of 79.5%. Further fermentation of cellulosic hydrolysate containing 95.3g l(-1) glucose was performed using Saccharomyces cerevisiae 316, and 45.7g l(-1) ethanol was obtained within 18h. The research results are meaningful in fuel ethanol production from agricultural residue instead of grain starch. (c) 2006 Elsevier Ltd. All rights reserved.