Biocontrol and bioprotection potential of selected non-Saccharomyces yeasts in grape and wine production.

In recent years, a key objective of the wine industry is the reduction of fungicide application in vineyard and sulphur dioxide (SO₂) during wine production, thereby encouraging alternative preservation methods. To address this objective, four non-Saccharomyces yeast species were evaluated in two independent experiments for their potential use as biocontrol and bioprotective agents. First, the selected yeasts were sprayed on Vitis vinifera L. cv. Nebbiolo grapes and evaluated as potential biocontrol agents against post-harvest grey mould caused by Botrytis cinerea. In parallel, the same strains were evaluated for their bioprotective ability against Hanseniaspora uvarum during the pre-fermentative stage and for their subsequent influence on fermentation dynamics and wine characteristics, both in fermentations conducted without Saccharomyces cerevisiae inoculation and in sequential fermentations with S. cerevisiae. The results demonstrated that all yeast treatments significantly reduced grey mould incidence on grapes compared to the controls. Among the tested species, Metschnikowia pulcherrima and Torulaspora delbrueckii were found to be the most effective, achieving a level of disease control comparable to that obtained with the control conventional chemical fungicide. Microbiota analysis revealed a good development of the yeasts on the treated bunches, along with a reduction of the Botrytis genus abundance. During fermentation, tested species inhibited H. uvarum, with T. delbrueckii showing the strongest effect. Wine quality was influenced by the applied non-Saccharomyces species. Overall, these findings highlight the potential of selected antagonistic yeasts as effective and sustainable alternatives to chemical fungicides and SO2 for microorganisms' control in the grape-to-wine ecosystem.