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Influence of phytosterols and ergosterol on wine alcoholic fermentation for Saccharomyces cerevisiae strains
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Edité par CCSD -
International audience. Sterols are a fraction of the eukaryotic lipidome that is essential for the maintenance of the cell membraneintegrity and their good functionality. During alcoholic fermentation, they ensure yeast growth,metabolism and viability, as well as resistance to osmotic stress and ethanol inhibition. Two sterol sourcescan support yeasts to adapt to fermentation stress conditions: ergosterol, produced by yeast in aerobicconditions, and phytosterols, plant sterols found in grape musts imported by yeasts in anaerobiosis. Little isknown about the physiological impact of the assimilation of phytosterols in comparison to ergosterol andthe influence of sterol type on fermentation kinetics parameters. Moreover, studies done until todayanalyzed a limited number of yeasts strains. For this reason, the aim of this work is to compare thefermentation performances of 27 Saccharomyces cerevisiae wine strains with phytosterols and ergosterolon two conditions: sterol limitation and osmotic stress (the most common stress during fermentation dueto high concentrations of sugars). Experiments were performed in 300 mL fermenters without oxygen andmonitored in order to obtain kinetics parameters. Cell count and cell viability were measured around 80%of fermentation progress. Central carbon metabolism (CCM) metabolites were quantified at the end offermentation. Principal Component Analysis revealed the huge phenotype diversity of strains in this study.Analysis of variance indicated that both the strain and the type of sterol explained the differences on yeastfermentation performances. Strains with a high viability at the end of the fermentation finished fermentingearlier. Finally, ergosterol allowed a better completion of fermentation in both stress conditions tested.These results highlighted the role of sterols in wine alcoholic fermentation to ensure yeast growth andavoid sluggish or stuck fermentations. Interestingly, sterol type affected yeast viability, biomass, kineticsparameters and biosynthesis of CCM metabolites.
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