Journal of Bioprocessing & Biotechniques

Enhanced Saccharification of Steam-Pretreated Rice Straw by Commercial Cellulases Supplemented with Xylanase

Abstract

Jairam Choudhary, Saritha M, Lata Nain and Anju Arora

For successful commercialization of biomass to ethanol process, the techno- economic hurdles have to be overcome. Complete substrate utilization is the key for making economics favorable. Existing enzyme preparations do not give high saccharification efficiency, thus, a broader suite of hydrolases is required. Xylanase supplementation in enzyme cocktail is an important strategy to increase sugar yields. In our study, hyperxylanolytic Aspergillus awamori F18 was used to produce xylanase. A. awamori F18 expressed high levels of xylanase during Solid state fermentation of corncob and also, Carboxy Methyl Cellulase (CMCase), filter paper activity (FP lyase) and β-glucosidase (524.43, 43.95, 8.64 and 29.81 IU mg-1 proteins respectively). A 10.6-12.5 fold concentration of these activities was achieved by single-step acetone precipitation. Supplementing concentrated xylanase to Accellerase®1500 resulted in 69.5% enhancement in sugars released after 72 h of saccharification of steam-pretreated rice straw. HPLC analysis of hydrolysates showed higher glucose levels along with the presence of xylose and arabinose. There was a 12.4% increase in the amounts of glucose as well as total sugars released when xylanase was supplemented to commercial cellulase and β-glucosidase.