Improvement of Ethanol Tolerance by Inactive Protoplast Fusion inSaccharomyces cerevisiae

Abstract

Saccharomyces cerevisiaeis a typical fermentation yeast in beer production. Improving ethanol tolerance ofS. cerevisiaewill increase fermentation efficiency, thereby reducing capital costs. Here, we found thatS. cerevisiaestrain L exhibited a higher ethanol tolerance (14%, v/v) than the fermentative strain Q (10%, v/v). In order to enhance the strain Q ethanol tolerance but preserve its fermentation property, protoplast fusion was performed with haploids from strain Q and L. The fusant Q/L-f2 with 14% ethanol tolerance was obtained. Meanwhile, the fermentation properties (flocculability, SO2production,α-N assimilation rate, GSH production, etc.) of Q/L-f2 were similar to those of strain Q. Therefore, our works established a series of high ethanol-tolerant strains in beer production. Moreover, this demonstration of inactivated protoplast fusion in industrialS. cerevisiaestrain opens many doors for yeast-based biotechnological applications.