Phenotypic Landscape of Saccharomyces cerevisiae during Wine Fermentation: Evidence for Origin-Dependent Metabolic Traits

The species Saccharomyces cerevisiae includes natural strains, clinical isolates, and a large number of strains used in human activities. The aim of this work was to investigate how the adaptation to a broad range of ecological niches may have selectively shaped the yeast metabolic network to generate specific phenotypes. Using 72 S. cerevisiae strains collected from various sources, we provide, for the first time, a population-scale picture of the fermentative metabolic traits found in the S. cerevisiae species under wine making conditions. Considerable phenotypic variation was found suggesting that this yeast employs diverse metabolic strategies to face environmental constraints. Several groups of strains can be distinguished from the entire population on the basis of specific traits. Strains accustomed to growing in the presence of high sugar concentrations, such as wine yeasts and strains obtained from fruits, were able to achieve fermentation, whereas natural yeasts isolated from “poor-sugar” environments, such as oak trees or plants, were not. Commercial wine yeasts clearly appeared as a subset of vineyard isolates, and were mainly differentiated by their fermentative performances as well as their low acetate production. Overall, the emergence of the origin-dependent properties of the strains provides evidence for a phenotypic evolution driven by environmental constraints and/or human selection within S. cerevisiae

Nitrogen demand of different yeast strains during alcoholic fermentation. Importance of the stationary phase

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Use of constant rate alcoholic fermentations to compare the effectiveness of different nitrogen sources added during the stationary phase

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Regulation of alcoholic fermentation rate by assimilable nitrogen addition. Comparison of different nitrogen sources

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Effectivness of combined ammoniacal nitrogen and oxygen additions for completion of sluggish and stuck wine fermentations

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Effet de la maturité et du millésime sur la fermentescibilité des moûts

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Effect of variety, year, and grape maturity on the kinetics of alcoholic fermentation

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Isolation and Characterization of Clostridium butyricum DSM 5431 Mutants with Increased Resistance to 1,3-Propanediol and Altered Production of Acids

Clostridium butyricum mutants were isolated from the parent strain DSM 5431 after mutagenesis with N-methyl-N(prm1)-nitro-N-nitrosoguanidine and two selection procedures: osmotic pressure and the proton suicide method. Isolated mutants were more resistant to glycerol and to 1,3-propanediol (1,3-PD) than was the wild type, and they produced more biomass. In batch culture on 62 g of glycerol per liter, the wild type produced more acetic acid than butyrate, with an acetate/butyrate ratio of 5.0, whereas the mutants produced almost the same quantities of both acids or more butyrate than acetate with acetate/butyrate ratios from 0.6 to 1.1. The total acid formation was higher in the wild-type strain. Results of analysis of key metabolic enzymatic activities were in accordance with the pattern of fermentation product formation: either the butyrate kinase activity increased or the acetate kinase activity decreased in cell extracts of the mutants. A decreased level of the hydrogenase and NADH-ferredoxin activities concomitant with an increase in ferredoxin-NAD(sup+) reductase activities supports the conclusion that the maximum percentage of NADH available and used for the formation of 1,3-PD was higher for the mutants (97 to 100%) than for the wild type (70%). In fed-batch culture, at the end of the fermentation (72 h for the wild-type strain and 80 to 85 h for the mutants), 44% more glycerol was consumed and 50% more 1,3-PD was produced by the mutants than by the wild-type strain