ROS accumulation and oxidative damage to cell structures in Saccharomyces cerevisiae wine strains during fermentation of high-sugar-containing medium

To further elucidate the impact of fermentative stress on Saccharomyces cerevisiae wine strains, we have here
evaluated markers of oxidative stress, oxidative damage and antioxidant response in four oenological strains
of S. cerevisiae, relating these to membrane integrity, ethanol production and cell viability during
fermentation in high-sugar-containing medium. The cells were sampled at different fermentation stages
and analysed by flow cytometry to evaluate membrane integrity and accumulation of reactive oxygen species
(ROS). At the same time, catalase and superoxide dismutase activities, trehalose accumulation, and protein
carbonylation and degradation were measured. The results indicate that the stress conditions occurring
during hypoxic fermentation in high-sugar-containing medium result in the production of ROS and trigger an
antioxidant response. This involves superoxide dismutase and trehalose for the protection of cell structures
from oxidative damage, and protein catabolism for the removal of damaged proteins. Cell viability, membrane
integrity and ethanol production depend on the extent of oxidative damage to cellular components. This is, in
turn, related to the ‘fitness’ of each strain, which depends on the contribution of individual cells to ROS
accumulation and scavenging. These findings highlight that the differences in individual cell resistances to
ROS contribute to the persistence of wine strains during growth under unfavourable culture conditions, and
they provide further insights into our understanding of yeast behaviour during industrial fermentation.