Improved Ethanol and Reduced Xylitol Production from Glucose and Xylose Mixtures by the Mutant Strain of Candida shehatae ATCC 22984

A mutant Cs3512, which showed better fermentation of xylose and the mixtures of xylose and glucose, was obtained through mutation of Candida shehatae ATCC 22984 and screening with a medium containing antimycin A and TTC (2,3,5-triphenyltetrazolium chloride). Cs3512 produced 44.4 g/l of ethanol from 121.3 g/l of xylose, which was 13% higher than that by ATCC 22984. At the same time, xylitol production was reduced by 38% to 10.2 g/l from 16.3 g/l by ATCC 22984. Cs3512 also showed 8% increase in ethanol yield from 0.39 to 0.42 g/g comparing to ATCC 22984 when fermenting the sugar mixture composed of 52.9 g/l glucose and 21.2 g/l xylose. When Cs3512 was used in the simultaneous saccharification and fermentation of lime pretreated rice straw via CaCCO (calcium capturing by carbonation) process, it produced ethanol at 77% of the theoretical yield. The results imply that Cs3512 is a potential non-recombinant yeast strain for ethanol production from lignocellulosic biomass.