Résumé
In oenological fermentation, proper wine yeast nutrition is crucial for ensuring efficient and safe fermentations. While yeast-available nitrogen (YAN) remains a significant factor, recent research underscores the importance of other micronutrients, such as sterols, at a balanced concentration in grape must for successful fermentation. This study emphasizes the essential role of sterols during alcoholic fermentation.Saccharomyces cerevisiae utilizes two primary sterol sources to adapt to fermentation stress conditions: ergosterol, produced by yeast cells during aerobic growth, and phytosterols, synthesized by plants and encountered in the grape must. These two sterols are imported by yeast during anaerobic fermentation. However, the physiological impact during alcoholic fermentation of assimilating phytosterols compared to ergosterol and the influence of the sterol type are poorly understood.This research investigated the sterol requirements of 27 commercial wine Saccharomyces cerevisiae strains in a synthetic grape must with a high sugar content, mimicking the nutritional imbalances induced by climate change. The variability of the strain’s behavior, in these fermentation conditions, suggests that some strains are better equipped to handle lipid limitations. The study also found that the origin of the sterols (phytosterols vs. ergosterol) significantly affects main fermentation parameters like yeast population, viability, and fermentation rate, often with a connection to nitrogen assimilation. Additionally, an impact on the final wine aroma profile was observed.Finally, transcriptomic analyses have shed light on the molecular mechanisms underlying the observed differences between ergosterol and phytosterol limitations. By affecting the stability of yeast cell membranes, sterols can optimize overall yeast metabolism, leading to improved control over the fermentation process and aroma production.