Impact of strain and inoculation time on yeasts interactions: mass spectrometry-based study.

Abstract

Under oenological conditions, when yeasts grow simultaneously during alcoholic fermentation, they often do not coexist passively, and in most cases, physiological and metabolic interactions are established between them. They interact by producing unpredictable compounds and fermentation products that can affect the chemical composition of the wine and therefore alter its aromatic and sensory profile. With its great resolution and excellent mass accuracy, ultrahigh resolution mass spectrometry (uHRMS) is the perfect tool to analyze the yeast metabolome at the end of alcoholic fermentation.

In this study, we aimed to characterize different non-Saccharomyces (NS) yeast species and to study the influence of these strains in sequential cultures with Saccharomyces cerevisiae (S). We show that tremendous differences exist between species in terms of metabolites, and we could clearly differentiate wines according to the yeast strain used in single cultures and markers, which reflect important differences between the yeast species. uHRMS was able to distinguish thousands of metabolites and provides deep insights into grape must composition allowing better understanding of the yeast-yeast interactome. Single cultures could be easily discriminated from sequential cultures based on their metabolite profile. New metabolites appeared in wines from sequential fermentation compared to single fermentation. The dominance of S, characterized by a metabolic richness not found with NS, is dependent on inoculation time and on the yeast species present. The wine composition of sequential culture is not only the addition of metabolites from each species but is the result of complex interactions. Co-inoculation leads to the formation of new compounds, reflecting a reshuffling of yeast metabolism linked to interaction mechanisms.