Résumé
During winemaking fermentation, the main sources of assimilable nitrogen for yeasts in grape musts areammonium and free amino acids; however, secondary sources such as oligopeptides are also importantcontributors to the nitrogen supply. Saccharomyces cerevisiae contains different peptide transporters:Ptr2 and Dal5, specific to di- and tri-peptides, whereas the Oligopeptide transport (OPT) family membersimport tetra- and pentapeptides (1). Furthermore, Fungal Oligopeptide Transporters (FOT) are a novelfamily of oligopeptide transporters found in fungi. In S. cerevisiae, at least 3 genes (FOT1, FOT2 and FOT3)are found mainly in wine strains as a result of a horizontal gene transfer from the yeast Torulasporamicroellipsoides, which contains FOTX and FOT2Tm in tandem as well as the FOTY gene outside thedonated region to S. cerevisiae (2). In the S. cerevisiae commercial wine strain EC1118, Fot1 and Fot2 areresponsible for a broader range of oligopeptide utilization, which leads to a better fermentation efficiencyand cell viability and the production of positive organoleptic compounds in wine when compared to theFot-knockout strain counterparts (2, 3). These results evidenced the adaptive advantage conferred by Foton S. cerevisiae within the wine environment. Despite the importance of oligopeptides on yeastmetabolism during fermentation, their role has long been underestimated. In our recent work, we havecharacterized oligopeptide transport in S. cerevisiae. Since Fot family members display a high sequenceidentity, from 90% to 98% at gene level (2), we have explored the oligopeptide transport specificity ofeach Fot member using Biolog phenotype microarrays (4). For this purpose, we have constructed S.cerevisiae strains containing each different Fot as the sole oligopeptide transporter using CRISPR/Cas9system. Strains expressing single FOT genes had different profiles of peptide consumption, indicating thediversity in Fot substrate specificities. Considering the high sequence identity, this result indicated thatsequence divergence among Fot can be crucial for transport activity. In a second step of this project, wehave evaluated the effect of peptide addition on fermentation kinetics and aroma production inoenological conditions with a large pool of commercial yeasts (5). We have compared the effect of a“classic” assimilable nitrogen addition (ammonium + amino acids) to the addition of digested serumalbumin bovine (BSA); these fermentations were performed in both white and red musts, screening 18 S.cerevisiae commercial strains. We showed that peptide addition enhances fermentation kinetics andleads to specific changes in the aroma production. This work highlights the importance of peptides inalcoholic fermentation and the oligopeptide transport diversity, providing a novel frame for nitrogenmanagement in oenological fermentation.