Improving the Cryotolerance of Wine Yeast by Interspecific Hybridization in the Genus Saccharomyces

Abstract

Fermentations carried out at low temperatures (10-15°C) enhance the production and retention of flavor volatiles, but also increase the chances of slowing or arresting the process. Notwithstanding, as Saccharomyces cerevisiae is the main species responsible for alcoholic fermentation, other species of the genus Saccharomyces, such as cryophilic species Saccharomyces eubayanus, Saccharomyces kudriavzevii and Saccharomyces uvarum, are better adapted to low-temperature fermentations during winemaking. In this work, a Saccharomyces cerevisiae × S. uvarum hybrid was constructed to improve the enological features of a wine S. cerevisiae strain at low temperature. Fermentations of white grape musts were performed, and the phenotypic differences between parental and hybrid strains under different temperature conditions were examined. This work demonstrates that hybridization constitutes an effective approach to obtain yeast strains with desirable physiological features, like low-temperature fermentation capacity, which genetically depend on the expression of numerous genes (polygenic character). As this interspecific hybridization approach is not considered a GMO, the genetically improved strains can be quickly transferred to the wine industry.

Keywords: Saccharomyces cerevisiae; Saccharomyces uvarum; hybrids; low temperature; must fermentation; winemaking.

FIGURE 1

Box plot representation of the μ_max distribution in all the strains within the assayed complete temperature range. Growth was performed in a synthetic must (A) and in a complete lab medium (B).

FIGURE 2

Dendrograms showing the phenotypic relationships among different strains according to temperature behavior in the synthetic must (A) and the complete lab medium (B). Data was provided in form of distance matrix.

FIGURE 3

Maximum specific growth rate of each tested species within the whole assayed range of temperatures in SM (A) and the complete lab medium (B). Values are expressed as the mean of the μ_max of all the strains belonging to the same species.

FIGURE 4

Maximum specific growth rate (h^-1) of the best 10 Saccharomyces strains grown at 15°C in the complete lab medium (LM). Dark and light blue highlight the strains with the highest cell percentages in the competition test.

FIGURE 5

Growth parameters of the three segregants compared with parental strains S. cerevisiae ADY18 and S. uvarum ADY59 in the synthetic must (SM). (A) Maximum specific growth rate and (B) area under the curve (AUC). ^a Significant differences compared with the ADY18 strain. ^b Significant differences compared with both parental strains.