Proteomic and metabolomic study of wine yeasts in free and immobilized formats, subjected to different stress conditions

Abstract

The aroma of wine is the first sensory perception that affects its quality. The knowledge acquired to date ensures that the unique aroma of a specific wine is the result of the sensation that in our sense of smell cause the molecules of more than 800 volatile compounds present in the hydroalcoholic solution that is the wine.These compounds come from the grapes, the prefermentative treatments, the alcoholic fermentation and the aging or preservation of the wine. It is a proven fact that fermentative yeasts exert an important influence on the aroma of wine, because they excrete odorant molecules to the medium which are products of their metabolism. Winemaking is a highly-skilled biotechnological process where a large number of commercial strains of Saccharomyces and non-Saccharomyces yeasts have been selected for their ethanol and/or flavour compounds production and comerciallized. During winemaking, yeast cells undergo different stress conditions, including high osmotic pressure induced by sugar content, increased concentration of ethanol, reactive oxygen species (ROS) derived from oxygen metabolism and high temperature. Yeasts cope with these conditions by adapting their response of their biological information system (genometranscriptome- proteome-metabolome) in order to prevent induced cell dysfunctions and to acquire stress tolerances. On the other hand, it has been verified that the immobilized yeasts present better behavior than the free yeasts against certain stress conditions. An example is the formation of flor velum biofilm by some strains of Saccharomyces cerevisiae to tolerate elevated contents in ethanol. The response of yeast S. cerevisiae to stress conditions has been studied fundamentally from the genomics and transcriptomics point of view. Studies on the production of ethanol and volatile compounds related to aroma and sensorial quality of wine are also numerous. However, the proteome of yeasts under different stress conditions and their relationship with volatile metabolites excreted in the medium is a line of research little explored until the present moment. The wine industry needs yeasts that are better adapted to grow under different stress conditions because of its interest in the elaboration of new types of wine according to the consumer preferences. Elucidating the proteomic response of yeasts to different stress conditions and knowing how this response affects the aroma-related metabolites are highly important for the selection and genetic improvement of yeast strains used in the alcoholic fermentation industries in general and wine in particular.