Résumé
In the increasingly competitive worldwide market of wines, a current challenge for winemakers is to offer products with style and character to meet the consumer’s expectations. In this context, controlling the production of volatile compounds during the fermentation, which may have a positive or negative incidence on the wine aroma, is essential. This project focuses on the understanding of the formation of volatile sulfur compounds (VSCs) deriving from yeast metabolism and described as unpleasant aromas in wines. The yeast metabolic network underlying the synthesis of these molecules remains until now poorly elucidated as well as the incidence on the activity of these pathways of many environmental and technological parameters including pH, sugars, sugar concentration, nitrogen resource composition and availability or SO2 addition. To address these issues, we first explored the diversity within a collection of 45 yeasts (Saccharomyces and non Saccharomyces species) commonly encountered in wine environment in their abilities to produce VSCs (15 analysed compounds), revealing an important variability between strains. Then, using a Box-Behnken experimental design, we were able to assess the impact of 5 parameters (pH, temperature, nitrogen, sugar and SO2 concentrations) and their interactions on the fermentation performances, the production/consumption of SO2 and the formation of VSCs by high and low producer strains. These data, combined with transcriptomic approaches and functional analysis of target genes will allow us to understand the regulation mechanisms underlying the formation of VCSs during fermentation. Overall, this study, providing new insights on the modulation by environmental factors of the production of VSCs by yeasts, will allow to define efficient strategies to reduce the formation of VSCs during winemaking.