Shotgun proteomics reveals interactions between Starmerella bacillaris and Saccharomyces cerevisiae during sequential wine fermentation

The use of non- Saccharomyces yeasts species in sequential fermentation with Saccharomyces cerevisiae has gained increasing attention due to their biotechnological and sustainability potential in the wine industry. Species such as Starmerella bacillaris, when used in combination with Saccharomyces cerevisiae , have been shown to significantly enhance wine aroma complexity, elevate glutathione and glycerol levels, and reduce ethanol and acetic acid concentrations. Moreover, sequential fermentation increases the release of yeast cell wall components, particularly mannoproteins and polysaccharides, which contribute haze reduction and minimize the need for non-recyclable additives. In this context, examining cell wall modifications could contribute to a better understanding of yeast-to-yeast interactions during alcoholic fermentation. Therefore, this study investigates proteome dynamics at three time-points during sequential fermentation of S. bacillaris FRI751 and S. cerevisiae EC1118, with a specific focus on cell wall-associated proteins. Results reveal that S. bacillaris exerts a substantial influence on S. cerevisiae proteome, modulating the expression of proteins related to cell wall management, either directly, by remodeling its structure or indirectly by modifying plasma membrane components that affect the cell wall. The sequential fermentation leads to an accelerated reduction of Starmerella key cell wall enzymes, suggesting that S. cerevisiae may inhibit or slow the growth of this non- Saccharomyces yeast. This premature reduction of active growth-phase enzymes could affect the release of cell wall components into the wine, with potential effects on wine quality.