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Oliver Harlé1, Judith Legrand3, Catherine Tesnière2, Martine Pradal2, Jean-Roch Mouret2, Thibault Nidelet2*

Affiliations : 1 : STLO, INRA, Agrocampus Ouest, Rennes, France 2 : SPO, Univ Montpellier, INRA, Montpellier SupAgro, Montpellier, France 3 : GQE-Le Moulon, INRA, Univ. Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, 91190 Gif-sur-Yvette, France

• Corresponding Author: [email protected]

keywords: winemaking fermentation, yeast-yeast interactions, population dynamics, non-Saccharomyces species, transgressive interactions, ecosystems

Abstract Fermentation by microorganisms is a key step in the production of traditional food products such as bread, cheese, beer and wine. In these fermentative ecosystems, microorganisms interact in various ways (competition, predation, commensalism and mutualism). Traditional wine fermentation is a complex microbial process performed by different yeast species which can be classified in two groups: Saccharomyces and non-Saccharomyces species. To better understand the different interactions occurring within wine fermentation, isolated cultures were compared to cultures involving one reference strain of S. cerevisiae species and one strain of five non-Saccharomyces yeast species out of five (Metschnikowia pulcherrima, Metschnikowia fructicola, Torulaspora delbrueckii, Hanseniaspora opuntiae and Hanseniaspora uvarum). In each case, we studied the population dynamics, the resources consumption and the production of metabolites of central carbon metabolism. This deep phenotyping of competition kinetics allowed us to identify the main mechanisms of interaction. T. delbrueckii and S. cerevisiae compete for resources with comparable fitness in our experimental conditions. S. cerevisiae and H. uvarum and H. opuntiae are also competing for resources although both Hanseniaspora strains are characterized by a strong mortality in isolated and mixed fermentations. M. pulcherrima and M. fructicola have a negative interaction with S. cerevisiae, provoking a decrease in viability in co-culture, probably caused by the synthesis of a killer toxin. Overall, this work highlights the interest of measuring the population and metabolites kinetics in order to understand yeast-yeast interactions. These results are a first step for ecological engineering and the intelligent design of optimal multi-starter consortiums using modeling tools.