New insights into the capacity of commercial wine yeasts to grow on sparkling wine media. Factor screening for improving wine yeast selection

• Growth capacity of commercial wine yeast strains was studied in defined wine medium (DWM) with increasing levels of ethanol.
• The negative effect of low pH on growth parameters was confirmed.
• A negative effect of glycerol content in the DWM on growth parameters was observed.
• Cysteine allowed yeast cells to tolerate the negative effect of medium-chain fatty acids better.
• The modification of cell fatty acid composition seemed to modify both the estimated NIC and MIC slightly.

During the production of sparkling wine, wine yeasts are subjected to many stress factors apart from ethanol, which lead to the need to achieve their acclimation in line with various industrial protocols. In the present work, 44 commercial wine Saccharomyces cerevisiae strains and one laboratory strain (BY4742) were firstly subjected to the influence of increasing concentrations of ethanol to cluster the yeasts using discriminant function analysis. Afterwards, non-inhibitory concentration (NIC) and minimum inhibitory concentration (MIC) were estimated, revealing some differences between 24 of these strains. Meanwhile, this study confirms the negative synergistic effect of low pH with ethanol on the maximum specific growth rate (μmax) and lag phase time. Moreover, a negative effect of increasing levels of glycerol in the growth medium was observed. Interestingly enough, an interactive positive effect was found between cysteine and medium-chain fatty acids (MCFA). While cysteine did not have a really significant effect in comparison to the control, it was able to restore the damage caused by MCFA, making the growth rate of cells recover and even reducing the formation of reactive oxygen species. Adequate culture aeration is also crucial for the composition of the cell fatty acid. The final results showed that few differences were observed between NIC and MIC estimations with respect to cells pre-cultured in the presence or absence of oxygen.