A novel integrated process to convert cellulose and hemicellulose in rice straw to biobutanol

A novel integrated process was established in this study to produce butanol from rice straw. In the first pretreatment, an alternative NaOH/Urea preatment operated at -12 ^oC efficiently removed 10.9 g lignin and preserved 91.54% cellulose and hemicellulose in 100 g rice straw. Subsequently, crude cellulase produced from Trichoderma viride was used to convert pretreated rice straw to mono-sugars for fermentation. The yields of glucose, xylose and arabiose obtained from 100 g rice straw were 31 g, 13.4 g and 0.48 g, respectively, resulting in a 69.45% saccharification efficiency of crude enzyme. Finally, to alleviate the carbon catabolite repression (CCR) and enhance butanol production, the coculture system of Clostridium beijerinckii and Saccharomyces cerevisiae was applied. Compared to monoculture of C. beijerinckii F-6, more sugars were consumed, especially the reduction rate of xylose reached to 81.87%, 32.99% higher than that in monoculture system. With more substrate facilitied into metabolism, the butanol concentration reached to 10.62 g/L corresponding to 0.28 g/g substrate, 115.38% higher than that in monoculture system. Overall, this integrated process was a low-energy consumption and efficient method for butanol production from rice straw.