Recycling Rice Straw into Biofuel "Ethanol" by Saccharomyces cerevisiae and Pichia guilliermondii

Abstract

This study suggests a new effective chemical pretre atment to hydrolyze rice straw for efficient ethanol production. It introduces a new y east strain that ferments rice straw hydrolyzate more efficiently than Saccharomyces cerevisiae . The results proved the effectiveness of alkali application before HCl to d elignify rice straw and to make it more appropriate for hydrolysis. The application of the hydrolyzing enzymes (cellulase and pectinase) resulted in hydrolysis of pretreated ric e straw up to 94.3% . The total sugars released due to pretreatment-enzyme system was abou t 624 mg g –1 dry mass and the glucose fraction was 198 mg g –1 . The results indicated that Pichia guilliermondii is more effective to ferment rice straw hydrolyzate than S. cerevisiae . P. guilliermondii produced larger amounts of bioethanol (7.72 g L –1 ) than S. cerevisiae (6.13 g L –1 ) under the same conditions. Our results suggest an appropriate pret reatment system (the cold dilute alkali-acid) and a new effective yeast strain to fe rment the rice straw hydrolyzate to produce large amounts of bioethanol. Keywords: Bioethanol, Hydrolysis , Pretreatment , Pichia guilliermondii, Rice straw, Saccharomyces cerevisiae .