Oxidative stress resistance during dehydration of three non-Saccharomyces wine yeast strains

The development of new fermented foods and beverages requires more and more the use of new dehydrated yeasts species. In this context, the non-Saccharomyces (NS) yeasts Torulaspora delbrueckii, Metschnikowia pulcherrima and Lachancea thermotolerans are developed especially in winemaking as co-culture in the fermentation of the must or for the must bioprotection. However, during formulation-dehydration the yeast cells are exposed to several stresses that reduce cellular activity. Among these, the oxidative stress induced by the stabilization processes has been described as one of the main causes of cell death. In this study, we analyzed the effects of growth medium associated with two dehydration kinetics on the accumulation of reactive oxygen species (ROS) and lipid peroxidation levels. The cultivability of tested yeast strains was dependent on growth and dehydration conditions. The L. thermotolerans strain was the most sensible to dehydration when growing in nutrient-poor media, which was characterized by high levels of ROS, lipid peroxidation and reduced cultivability. In contrast, this yeast was able to restore its cultivability when growing in nutrient-rich medium before dehydration. The other NS yeast strains acquired resistance to oxidative stress similarly but in a growth-dehydration condition less dependent manner. These results showed that modulation of growing medium composition is a simple way to improve resistance to oxidative attack imposed by dehydration in NS yeasts. This was the first time that multiple quantitative and qualitative indicators of oxidative stress response in these three NS yeast strains were explored.