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

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 0.5 M sodium carbonate at 100 ◦C and 1:20 g/g solid loading for 3 h. 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.