Enzymatic hydrolysis of microwave alkali pretreated rice husk for ethanol production by Saccharomyces cerevisiae, Scheffersomyces stipitis and their co-culture

Rice husk is one of the abundant lignocellulosic feed stocks in the world. It contains mixtures of pentose and hexose sugars, so selected for ethanol production. The microwave alkali pretreated rice husk enzymatically hydrolyzed with crude unprocessed hydrolytic enzymes. Concentrated enzymatic hydrolyzate having initial reducing sugar concentrations of 10 g/L, 25 g/L, 50 g/L and 70 g/L were used for ethanol production. Fermentation was accomplished by the action of yeast Saccharomyces cerevisiae, Scheffersomyces stipitis and their co-culture. Ethanol yield obtained with S. cerevisiae were 0.3 g/g, 0.35 g/g, 0.40 g/g and 0.39 g/g; with S. stipitis were 0.24 g/g, 0.27 g/g, 0.36 g/g and 0.35 g/g; and with co-culture of both were 0.33 g/g, 0.36 g/g, 0.42 g/g and 0.40 g/g with different sugar concentrations. Maximum ethanol yield was found to be 0.42 g/g with co-culture, 0.40 g/g with S. cerevisiae and 0.36 with S. stipitis at initial reducing sugar concentration of 50 g/L.