Specific Point Mutations in the RRT5 Gene Modulate Fermentative Phenotypes of an Industrial Wine Yeast

Saccharomyces cerevisiae is a yeast species of industrial importance due to its role in the production of several alcoholic beverages, including wine. During wine fermentation, S. cerevisiae must be able to cope with several stresses, such as limited nitrogen availability; nitrogen deficiencies in grape must could lead to stuck or sluggish fermentations, generating for the wine industry significant economic losses. A microbiological alternative to this problem is the generation of yeast strains with low nitrogen requirements for fermentation. In this context, it is important to study the natural diversity regarding adaptation to low nitrogen conditions, especially in terms of searching for beneficial alleles with potential industrial applications. In the present work, we validated the impact of specific SNPs present in the RRT5 gene in an industrial genetic background (T73 strain), analyzing both growth kinetics under microculture conditions and fermentative phenotypes in a larger volume. In this way, we were able to validate that these SNPs do indeed have an impact on the growth kinetics and fermentative capabilities of this strain, although the particular effect depends on the type of must used (synthetic or natural) and the nitrogen content (limiting or non-limiting). In particular, one mutation (601A>C) caused slower fermentation kinetics in the nitrogen-limited natural must but did not affect the ethanol produced or the amount of sugars consumed, in addition to producing more glycerol and consuming less phenylalanine, which could have a positive impact on the organoleptic properties of the wine produced and therefore an industrial potential. To our knowledge, this is the first work linking RRT5 to fermentative phenotypes, and the genetic variants validated could have industrial potential for the wine industry.