Metabolomic study of mixed Saccharomyces cerevisiae yeast during fermentation

Abstract

Alcoholic fermentation conducted by microorganism is a key step in the production of wine. In this process, interactions between different species of yeast are widely described but their mechanisms are still poorly understood. The interactions studied in wine are mainly between Saccharomyces and non-Saccharomyces species. Therefore, little is known about the mechanisms of interactions between Saccharomyces cerevisiae strains in mixed culture, yet they are major actors that are in part responsible for the metabolic modifications within each strain and therefore for the quality of the final product. In order to better understand interactions occurring between two strains of S. cerevisiae, pure cultures were compared with mixed co-cultures and blend of wines using ultra high-resolution mass spectrometry, LC-MS, GC-MS and sensory analysis. Three mixed were studied, on the same Chardonnay must, each involving a common strain. Ultrahigh -resolution mass spectrometry (uHRMS) revealed important differences between pure cultures and mixed cultures. This work reports that mixed fermentation led to changes in chemical wine composition. Besides, we found that the blends showed a different chemical composition than mixed cultures. This indicates that the co-culture did not consist of the addition of two independent yeast metabolisms but of interaction events.  We also observed that depending on the strain associated to the common strain, there were interaction phenomena of different natures. These findings were further demonstrated by the volatilome study of 65 volatile compounds and sensory analysis. Indeed, a modulation of the volatile composition and sensory profile were noted when both strains were combined but also according to the strains involved in the fermentation.