Biocontrol Agents against Botrytis cinerea in Sustainable Winemaking: Impact on Fermentation and Wine Quality

The transition toward sustainable viticulture requires effective and environmentally friendly alternatives to synthetic fungicides. In this context, Botrytis cinerea, the causal agent of grey mould, represents a major challenge for grape production and wine quality, especially under increasingly restrictive regulations. This study explores the use of microbial biocontrol agents (BCAs) previously isolated from grapevine-associated microbiota—Metschnikowia reukaufii, M. hawaiiensis, and Aureobasidium pullulans—for the control of B. cinerea and their impact on winemaking. Microvinification trials were conducted on Vitis vinifera cv. Nebbiolo using both fresh and withered grapes. Treatments included co-inoculation of the selected BCAs with a Saccharomyces cerevisiae commercial strain and untreated controls with five replicates per treatment, using post-harvest grapes. These trials included fermentations performed immediately and three days after BCA application. Fermentations were carried out in 200 mL flasks with Müller valves, under standard red winemaking protocols including maceration, temperature control (20 °C), aeration, and punch-downs during active alcoholic fermentation. Initial sugar concentrations significantly differed between matrices: 194.5 g/L in fresh grapes and 327.66 g/L in withered grapes. Fermentation kinetics were monitored via CO₂ release, and microbial viability was assessed at 24, 48, and 72 hours. The final sampling occurred after weight stabilization over 48 hours. Fermentation lasted 20 days in fresh grapes and 54 days in withered grapes. Wines were analyzed for key oenological parameters: pH, titratable and volatile acidity, sugar and ethanol content, organic acid profile, phenolic compounds, volatile profiles, and sensory attributes. Preliminary findings indicate that BCAs persist during early fermentation stages without significantly altering ethanol yield or core wine chemistry, even in high-sugar matrices. This research demonstrates the compatibility of selected BCAs with standard winemaking and supports their integration into sustainable viticulture practices. These findings contribute to the development of safer, regulation-compliant alternatives to synthetic fungicides for managing B. cinerea while preserving wine quality.