Improved ethanol fermentation by promoter replacement of zinc responsive genes IPL1, PRP6 and RTC1 in Saccharomyces cerevisiae

Zinc sulfate is an important mineral nutrient for yeast stress tolerance. In this study, IPL1, PRP6, and RTC1 whose expression are responsive to zinc sulfate, were investigated on their effects on inhibitor tolerance and ethanol fermentation by Saccharomyces cerevisiae. Yeast strains were developed through replacing native promoters by the constitutive PGK1 promoter for these genes. The engineered yeast strains showed improved ethanol fermentation in the presence of acetic acid and mixed inhibitors. Meanwhile, enhanced ethanol titer from corncob hydrolysate was achieved, and up to 19.5% more ethanol was produced using the engineered yeast strain carrying the RTC1 promoter replacement. The results in this study provides basis for further engineering yeast strains to improve efficiency of lignocellulosic biorefinery.