Enhancing thermotolerance of self-flocculating yeast with UV and DES-induced mutagenesis

Employing thermo tolerant yeasts in ethanol fermentation has many advantages, such as reducing cooling costs, accelerating fermentation rates and decreasing contamination chances during the process. In this work, to improve the thermotolerance of self-flocculating yeast, the parental strain was treated with UV-irradiation and diethyl sulfate (DES), singly and in combination. Then, 44 mutant strains were obtained using 40°C as selection pressure, and 8 strains were determined to be good performers in terms of glucose utilization and final ethanol concentration at 40°C of fermentation temperature. Of the 8 strains, mutants UD1 and UD4 were finally identified as the best two variants with the highest temperature and glucose tolerance. Consequently, these two variants were successfully applied to very high concentration ethanol fermentation at high temperature.