Résumé
Currently, in the winemaking sector, there is a renewed interest of the use of non-Saccharomyces (non-Sacc.) species during the fermentation process. Long regarded as spoilage microorganisms, the potential of these yeasts to improve the sensory quality of wines is now recognized. However, due to their low adaptation to increasing concentrations of ethanol and to oxygen limitations, the non-Sacc. strains are unable to complete fermentation and must be used in combination with Saccharomyces cerevisiae strains, added in mixed or sequential inoculation. However, the use of the non-Sacc. species in wine industry remains poorly controlled because of the limited knowledge on the phenotypic characteristics of these strains and their effective incidence of their interactions with S. cerevisiae on the fermentation process. To fill this shortcoming, this study first focused on the characterisation of the phenotypic specificities of a non-Sacc. species from the wine environment, Metschnikowia pulcherrima. In particular, the metabolic and enzymatic potentialities of this species, as well as its nitrogen sources requirements and preferences were investigated. Then, thanks to a Box-Behnken experimental design, we analysed the incidence of the main components of the grape must, i.e. concentration of sugars, nitrogen and lipids, on the contribution of M. pulcherrima to sequential wine fermentation with S. cerevisiae, especially in terms of production of higher alcohols, esters and thiols. Overall, these results are of significance for the comprehension of M. pulcherrima metabolism and pave the way to a better management of this species during winemaking.