Sequential cellulase production, saccharification and ethanol fermentation using rice straw

Abstract

This study presents alkali pretreated rice straw for cellulase production using <i>Aspergillus niger </i>CP1 by solid state fermentation (SSF). On 8th day, 140±2.4 IU g/l dry substrate (ds) carboxy methyl cellulose CMCase), 15±1.2 IU g/l ds filter paper activity (FPA) and 24±1.1 IU g/l ds â-glucosidase activities were noted. On extraction of 120 g material with 1 l of 0.1 mol/l citrate buffer, 5.9±0.12 IU ml/l CMCase, 0.62±0.001 IU ml/l FPA and 1.11±0.002 IU/ml â-glucosidase were obtained. When extracted enzyme was used for saccharification of 120 g fresh pretreated rice straw containing 100 g holocellulose, 45±0.2 g, sugars (50 g/l) were released in 900 ml hydrolysate to give 45% hydrolysis. Hydrolysate after yeast fermentation gave 15.6±0.05 g/l ethanol with a yield of 0.4±0.011 g/l/h and 78% fermentation efficiency. In sequential enzyme production, saccharification and fermentation studies, on 8thday of cellulase production by SSF, temperature was shifted from 28±1°C to 55°C for 36 h, and 76% hydrolysis

was achieved. When <i>A. niger </i>in hydrolysate was inactivated and used, 68±0.83 g/l ethanol and 92% fermentation efficiency were obtained. Hydrolysate used without inactivation of <i>A. niger </i>gave 61.65±0.78 g/l ethanol and 85% fermentation efficiency.