Starmerella bacillaris Yeast Derivatives for Improving Wine Stability: Effect of Cell Wall Composition and Extraction Techniques

The use of yeast derivatives in winemaking is well established, with mannoproteins from Saccharomyces cerevisiae widely recognized for their role in reducing protein haze. However, non-Saccharomyces yeasts, particularly Starmerella bacillaris, are gaining interest as alternative sources of functional polysaccharides due to their distinct metabolic and structural features. This study investigated the production and application of mannoprotein-rich derivatives from S. bacillaris as novel stabilizing agents against protein haze in wine. Yeast cell wall from three S. bacillaris and two S. cerevisiae strains was obtained after propagation under industrial fed-batch conditions and subjected to heat, enzymatic, and alkaline extraction methods. The resulting extracts were chemically characterized and tested for their ability to enhance protein stability in white wine. Compositional analysis revealed structural differences between the two species, as all mannoprotein-rich derivatives from the cell wall of S. bacillaris contained a notably higher amount of glucose than those from S. cerevisiae. Moreover, protein profiling reported a distinct glycoprotein size distribution. These results suggest the presence in this non-Saccharomyces species of (gluco)mannoproteins of high molecular weight. Starmerella bacillaris derivatives exhibited higher efficacy in haze reduction compared to S. cerevisiae, particularly following alkaline treatment. These findings highlight the influence of yeast species and extraction strategy on derivative functionality and position S. bacillaris as a promising source of oenological additives for protein stabilization.