Résumé
Introduction: Saccharomyces cerevisiae ferments regardless of the presence of oxygen. However, thisCrabtree-positive yeast exhibits distinct metabolic responses to aerobic and anaerobic environments,particularly in settings such as wine fermentation. However, the underlying mechanisms andimplications of these adaptations remain incompletely characterised. This study aimed to elucidatethe differences in intracellular redox cofactor levels, ratios, and primary metabolite productionbetween aerobic and anaerobic conditions in S. cerevisiae.Methods: Fermentations in synthetic grape juice were conducted by S. cerevisiae under controlledaerobic and anaerobic conditions. Intracellular redox cofactor levels were quantified usingspectrophotometric assays, while primary metabolites were analysed using high-performance liquidchromatography. Transcriptomic analysis was conducted to investigate differences in geneexpression between the two conditions during the growth phase of the yeast.Results: Aerobic conditions exhibited enhanced fermentation kinetics and yeast growth compared toanaerobic conditions. Despite similar declines in total NAD(H) levels, cells under aerobic conditionsshowed a predominance of NADH over NAD+, and NADP(H) levels three times higher than underanaerobic conditions. Transcriptomic analysis revealed limited differential expression of genesinvolved in redox cofactor metabolism but indicated upregulation of genes related to lipid andvitamin B3 salvage pathways under anaerobiosis, amongst other noticeable changes.Conclusion: The study demonstrates distinct metabolic adaptations of S. cerevisiae to aerobic andanaerobic conditions, including differences in redox cofactor levels and gene expression profiles.These findings provide insights into the cellular mechanisms underlying yeast metabolism withpotential implications for industrial bioprocesses, such as wine fermentation. Indeed, manipulatingredox metabolism using oxygen could be used to modify product yields and efficiency in fermentativeproduction processes.