A breeding strategy to harness flavor diversity of Saccharomyces interspecific hybrids and minimize hydrogen sulfide production

Industrial food-grade yeast strains are selected for traits that enhance their application in quality production processes. Wine yeasts are required to survive in the harsh environment of fermenting grape must, while at the same time contributing to wine quality by producing desirable aromas and flavors. For this reason, there are hundreds of wine yeasts available, exhibiting characteristics that make them suitable for different fermentation conditions and winemaking practices. As wine styles evolve and technical winemaking requirements change, however, it becomes necessary to improve existing strains. This becomes a laborious and costly process when the targets for improvement involve flavor compound production. Here, we demonstrate a new approach harnessing preexisting industrial yeast strains that carry desirable flavor phenotypes - low hydrogen sulfide (H ₂S) production and high ester production. A low-H ₂S Saccharomyces cerevisiae strain previously generated by chemical mutagenesis was hybridized independently with two ester-producing natural interspecies hybrids of S. cerevisiae and Saccharomyces kudriavzevii. Deficiencies in sporulation frequency and spore viability were overcome through use of complementary selectable traits, allowing successful isolation of several novel hybrids exhibiting both desired traits in a single round of selection.