Reduction of ethanol yield and improvement of glycerol formation by adaptive evolution of a wine yeast Saccharomyces cerevisiae under hyperosmotic conditions.

We report an adaptive evolution methodology based on sequential increases of osmotic/saline stress to divert carbons toward glycerol and away from the production of ethanol. We used a commercial, diploid, heterozygous wine yeast strain EC1118 as parental. We studied in more detail six KCl-evolved strains producing high glycerol levels while retaining good fermentative performance, accumulating succinate and 2,3-butanediol. Mutants also exibit a better survival under salt stress and glucose restriction conditions. This six isolates were obtained after 200, 250, and 300 generations in two independent lineages: (a) K200.1(a), K250.1(a), K300.2(a), and (b), K200.1(b), K250.3(b), and K300.1(b). A QTL genetic analysis using a "bulk sequencing" approach was used to identify loci involved in the high glycerol and low ethanol traits.