Enhancing wine malolactic fermentation: Variable effect of yeast mannoproteins on Oenococcus oeni strains

Lactic acid bacteria (LAB), principally Oenococcus oeni, play crucial roles in wine production, contributing to the transformation of L-malic acid into L-lactic acid during malolactic fermentation (MLF). This fermentation is influenced by different factors, including the initial LAB population and wine stress factors, such as nutrient availability. Yeast mannoproteins can enhance LAB survival in wine. This study explored in model conditions the impact of a commercial mannoprotein extract on MLF dynamics in ten O. oeni strains. The results revealed strain-specific responses in fermentation kinetics and mannoprotein utilization. Mannoprotein addition influenced MLF outcomes, depending on the strain and concentration. The variability in MLF confirmed different technological aptitude of the strains used. The α-mannosidase enzymatic activity was determined and showed higher values in the supernatant than in whole cells. Moreover, α-mannosidase activity varied among strains, suggesting differential regulation in response to fermentation conditions. These findings highlight the importance of understanding mannoprotein interactions with O. oeni for optimizing MLF efficiency and enhancing wine quality. Further research under cellar conditions is needed to evaluate the potential of yeast mannoproteins to promote MLF.