A two-step process for efficient enzymatic saccharification of rice straw

Abstract

Response surface methodology was used to optimise a two-step process of cellulase mediated saccharification of rice straw by an isolated bacterium Lysinibacillus sphaericus. CMC concentration, yeast extract, pH and incubation temperature were optimised for cellulase production using a central composite design and their optimum values were determined to be 4.3% (w/v), 2.1% (w/v), 6.2 and 45.2 °C respectively. The CMCase activity at these values was 5.16±0.07 U/ml, which was 2.5 times that of the un-optimised system. Similarly, pretreated rice straw, enzyme load, incubation time and Tween-80 concentrations were optimised for enhanced saccharification of rice straw by optimised cellulase preparations, and their optimum values were calculated as 1.84% (w/v), 40 U, 57.4 h and 0.76 mM respectively. A percent saccharification of 69.5% was reported at optimal conditions. HPLC analysis revealed that hydrolysate produced at optimal conditions of saccharification constituted 70.8% of glucose.

Keywords: Cellulase production; Central composite design; Optimisation; Response surface methodology; Saccharification.