Production of cellulases by solid state fermentation with Aspergillus terreus and enzymatic hydrolysis of mild alkali-treated rice straw.

Rice straw was used as substrate for cellulase production by solid state fermentation with Aspergillus terreus. Substrate concentration, moisture ratio, inoculum size and initial pH were optimized using response surface methodology involving Box-Behnken design. The predicted filter paper activity under optimized parameters was 9.73 U/g and the validated filter paper activity was 10.96 U/g. Hydrolysis of the biomass pretreated with 0.125% to 1% NaOH for 24h at room temperature was performed using crude cellulase preparation. Treatment with 0.5% NaOH at room temperature for 24h was the most efficient treatment method for saccharification. Under the optimized conditions, rice straw yielded 676 mg reducing sugars per gram of substrate at a cellulase loading of 9 FPU g(-1) substrate. The present study establishes the possibility of using mild alkali pretreated rice straw for the production of fermentable sugars with 74.19% efficiency which can be further utilized for the production of ethanol.