Two-Stage Screening of Metschnikowia spp. Bioprotective Properties: From Grape Juice to Fermented Must by Saccharomyces cerevisiae

<i>Gluconobacter oxydans</i> (Go) and <i>Brettanomyces bruxellensis</i> (Bb) are detrimental micro-organisms compromising wine quality through the production of acetic acid and undesirable aromas. Non-<i>Saccharomyces</i> yeasts, like <i>Metschnikowia</i> species, offer a bioprotective approach to control spoilage micro-organisms growth. Antagonist effects of forty-six <i>Metschnikowia</i> strains in a co-culture with <i>Go</i> or <i>Bb</i> in commercial grape juice were assessed. Three profiles were observed against Go: no effect, complete growth inhibition, and intermediate bioprotection. In contrast, <i>Metschnikowia</i> strains exhibited two profiles against Bb: no effect and moderate inhibition. These findings indicate a stronger antagonistic capacity against Go compared to Bb. Four promising <i>Metschnikowia</i> strains were selected and their bioprotective impact was investigated at lower temperatures in Chardonnay must. The antagonistic effect against Go was stronger at 16 °C compared to 20 °C, while no significant impact on Bb growth was observed. The bioprotection impact on <i>Saccharomyces cerevisiae</i> fermentation has been assessed. <i>Metschnikowia</i> strains' presence did not affect the fermentation time, but lowered the fermentation rate of <i>S. cerevisiae</i>. An analysis of central carbon metabolism and volatile organic compounds revealed a strain-dependent enhancement in the production of metabolites, including glycerol, acetate esters, medium-chain fatty acids, and ethyl esters. These findings suggest <i>Metschnikowia</i> species' potential for bioprotection in winemaking and wine quality through targeted strain selection.