Enhanced thermotolerance and ethanol tolerance in Saccharomyces cerevisiae mutated by high-energy pulse electron beam and protoplast fusion

To increase thermotolerance and ethanol tolerance in Saccharomyces cerevisiae strain YZ1, the strategies of high-energy pulse electron beam (HEPE) and three rounds of protoplast fusion were explored. The YF31 strain had the characteristics of resistant to high-temperature, high-ethanol tolerance, rapid growth and high yield. The YF31 could grow on plate cultures up to 47?°C, containing 237.5?g?L^?1 of ethanol. In particular, the mutant strain YF31 generated 94.2?±?4.8?g?L^?1 ethanol from 200?g glucose L^?1 at 42?°C, which was 2.48 times the production of the wild strain YZ1. Results demonstrated that the variant phenotypes from the strains screening by HEPE irradiation could be used as parent stock for yeast regeneration and the protoplast fusion technology is sufficiently powerful in combining suitable characteristics in a single strain for ethanol fermentation.