Metschnikowia pulcherrima as biocontrol agent in white winemaking

Abstract

Biocontrol using non-Saccharomyces yeasts is an alternative strategy to chemical additives to prevent the growth of spoilage microorganisms. Metschnikowia pulcherrima exhibits strain-dependent antagonistic activity against undesired yeast populations in wine fermentations, effectively inhibiting their growth and preserving must quality. This study evaluates the antimicrobial capacity of three Metschnikowia pulcherrima indigenous strains (previously selected by in vitro antimicrobial assays) inoculated in single and co-culture in a Chardonnay must fermentation. The experimental trials involved inoculating the three strains and co-culture at 1×10⁶ cells/mL in must at 18°C, after a contamination with a mixed population of undesirable non-Saccharomyces yeasts (Brettanomyces bruxellensis, Kloeckera apiculata, and Starmerella bacillaris) at two initial concentrations (10⁴ or 10⁶ cells/mL) to mimic healthy and damaged grape conditions. After 48 hours, a commercial strain of Saccharomyces cerevisiae (EC1118 Lalvin) was inoculated to complete fermentation. The experiment was conducted in duplicate, daily monitoring CO₂ production (by weight loss), viable cell kinetics (plate counts on WL agar), and fermentation metabolites. The results showed that single and co-culture M. pulcherrima strains grew at concentrations ranging from to 6×10⁶ to 9×10⁶ cells/mL, inhibiting non-Saccharomyces yeasts. In particular, the highest antimicrobial activity was expressed by strain 27 and the co-culture that effectively inhibited the development of undesirable yeast species, allowing the S. cerevisiae strain to complete the fermentation in significantly shorter times than the trials inoculated by the other two M. pulcherrima strains. In conclusion, M. pulcherrima significantly contributed to preserving wine quality, reducing the growth of undesirable non-Saccharomyces yeasts in white winemaking.