Thiol groups are determinant for overcoming acetic acid and pH stress in wine and beer fermentation-derived Saccharomyces cerevisiae strains

: Acetic acid (AA), a natural by-product of ethanol fermentation in yeast cells, is widely present in lignocellulosic hydrolysate as a fermentation inhibitor. Thus, gaining insight into the molecular mechanisms of AA tolerance in yeast is particularly relevant for industrial applications. This study investigates the response to AA stress in two Saccharomyces cerevisiae strains (ATCC 9804 and ATCC 13007) during different metabolic states (fermentation, respiro-fermentation, and respiration) and external pH levels (3․0 and 4.5). The results show that AA reduces the viability of both strains in a dosage-dependent manner. Moreover, ATCC 13007 is more sensitive to AA stress compared to ATCC 9804. Respiratory metabolism and higher pH correlate with better resistance to AA stress. Catalase activity was observed to increase by 1.5-6-fold under AA stress conditions, in accordance with changes in yeast thiol group content and growth. The influence of AA stress is reactive oxygen species-dependent, and redox balance regulation was found to increase the robustness of S. cerevisiae ATCC 13007 to AA by 2-fold. The study reveals valuable insights into yeast adaptation to stress conditions, contributing to the development of robust yeast strain construction for high-yield biomass and chemicals production.