Harnessing the Enzymatic Potential of Indigenous Yeast Strains: Screening and Evaluation for Biocontrol and Oenological Advancements

The growing emphasis on sustainability, regional distinctiveness, and spontaneous fermentation in winemaking necessitates a more comprehensive understanding of local yeast populations and their functional mechanisms. In total, 115 indigenous yeast strains were examined for their enzymatic activities of potential vitivinicultural significance. The yeasts were screened for chitinase activity (biocontrol potential), glycosidase activity (terpene release), <i>β</i>-lyases (thiol release), and sulfite reductases (off-flavor formation), followed by quantitative analysis of the selected subsets. Yeasts were further evaluated for inhibition of fungal mycelial growth, VOC-mediated inhibition, and tolerance to commonly applied fungicides. Pre-field selection was refined using the niche overlap index and grapevine leaf disc assay. The results confirmed chitinolytic activity in four species; all strains exhibited hydrolase activities, with <i>H. uvarum</i> 116 displaying the highest cell-associated activity (6.32 U/g), while <i>T. delbrueckii</i> Sut94 showed the highest extracellular activity (1.36 U/g). <i>β</i>-glucosidase and <i>β</i>-lyase activities were widespread, whereas hydrogen sulfide production was infrequent. <i>P. guilliermondii</i> ZIM 624 showed the most comprehensive overall enzymatic profile, together with strong inhibition patterns. A field trial on Pinot cultivars (<i>V. vinifera</i> L.) further evaluated <i>P. guilliermondii</i> ZIM 624 within an integrated disease management approach, with responses being more pronounced in 'Pinot noir' than in 'Pinot gris'.