Influence of yeast adaptation with bio-activators on the process of wine alcoholic fermentation.

The initial stages of alcoholic fermentation are highly sensible to various external influences, making the ability of the fermenting strains to adapt to challenging conditions crucial for the success of the process. The performance of wine yeasts depends on their capacity to endure the harsh conditions of must fermentation. Saccharomyces cerevisiae strains consistently encounter unfavourable conditions during winemaking, such as low pH levels. This study investigated the effects of adding two commercial bio-activators (Adapta®, Hnutrix® B-Vitality) on fermentation performances and yeast cell response during the first 48 h of alcoholic fermentation. Additionally, the influence of a low pH environment (2.9) on the examined parameters was evaluated. Specifically, yeast levels were monitored over the initial 48h period post-inoculation using flow cytometry and plate counts. Furthermore, yeast RNA was converted into cDNA, and RT-qPCR was used to assess gene expression. Notably, in treatments with bio-activators, plate counts and flow cytometry showed that yeast levels reached higher levels 14 h after inoculation. Moreover, the presence of bio-activators enhanced cell viability, which could explain the improved fermentation rate observed in both standard and low pH conditions when the two bio-activators were used. The analysis of gene expression patterns revealed significant differences in treatment responses. Under low pH conditions, two markers related to radical scavenging mechanisms showed expression levels ten times higher than those under standard conditions. In conclusion, this study provides valuable insights into yeast cell physiology, highlighting how yeast cells adapt their responses during the initial stages of fermentation in challenging environments.