Ethanol production from rice straw by sodium carbonate pretreatment and Mucor hiemalis fermentation

Abstract

Rice straw, one of the most abundant and mainly unused lignocellulosic wastes, is a promising substrate for ethanol production. To improve ethanol production yield from the straw, pretreatment with sodium carbonate at mild conditions followed by fermentation using zygomycetes fungus Mucor hiemalis was performed. The sodium carbonate treatment was conducted at different concentrations, time intervals, and solid loadings. The highest glucose and ethanol production yields were obtained after the pretreatment with 0.5M sodium carbonate at 100°C and 1:20g/g solid loading for 3h. This pretreatment removed more than 90% of silica from the straw and improved the enzymatic hydrolysis yield from 35% to 100%. Afterward, ethanol was produced by simultaneous saccharification and fermentation (SSF) from the pretreated straw at 37°C using M. hiemalis, and the results were compared with SSF using Saccharomyces cerevisiae. The results showed that ethanol yield was improved by more than 40% under the optimum conditions and the yield was higher using M. hiemalis. Thus, the fungus could be a suitable alternative to S. cerevisiae for ethanol production from lignocellulosic wastes.