6533b7d2fe1ef96bd125dd1d

RESEARCH PRODUCT

Micro-organisms interactome during wine alcoholic fermentation

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The study of interactions between microorganisms is of major interest in oenology for various applications, including the modulation of the aromatic profile of wines. The interactions between Saccharomyces and non-Saccharomyces yeasts are widely described in the literature. On the contrary, interactions during alcoholic fermentation between S. cerevisiae strains, known for their technological properties in oenology, have been little studied.In this work, twelve strains of S. cerevisiae and their impact on wine were characterized in pure cultures using an integrative approach that combines microbiological, chemical, metabolomic and sensory approaches. An important intraspecific diversity was highlighted, leading to wines with specific chemical compositions and distinct sensory profiles. Four of these twelve strains were selected for their different metabolomic and sensory fingerprints in order to study the interactions between S. cerevisiae strains. To discriminate between strains of the same species using flow cytometry, tool of choice for real-time monitoring of growth kinetics, a gene coding for a fluorescent protein was integrated by CRISPR-Cas9 into the genome of one of these four selected strains. Although no phenotypic impact was observed, the integration of this gene had a significant effect on the metabolome and mainly the peptidome. 102 biomarkers specific to the modified strain or whose intensity was significantly modulated were revealed. The modified strain was integrated into co-cultures with each of the other three selected S. cerevisiae strains. These three co-cultures did not differ in population dynamics. On the other hand, their association to conduct alcoholic fermentation leads to wines with different chemical compositions than those from the associated pure cultures. Moreover, the wines from the co-cultures were remarkably different (metabolomically and sensorially) from the wine blends issued of the pure cultures. Esters, fatty acids and phenol families were affected by coculture regarding volatile compounds. High resolution mass spectrometry allowed to revealed thousands of coculture biomarkers. Metabolic pathways involved in these wine composition changes were highlighted and most belong to nitrogen metabolism including the pathways of amino acid metabolism, such as tryptophan and phenylalanine. Thus, non-neutral interaction phenomena were highlighted. It should be noted that interaction mechanisms differ according to the strains involved. It is necessary to take into account these phenomena when associating two strains whose impacts cannot be defined only according to the population dynamics. Understanding these phenomena will allow to optimize the use of mixed S. cerevisiae starter cultures in oenology.