Differentiation of Indigenous Saccharomyces cerevisiae Wine Strains by Oenological and Proteomic Characterization

Indigenous Saccharomyces cerevisiae strains persist within individual cellars and contribute to the character of spontaneously fermented wines, yet the molecular basis of their oenological differences remains largely unknown. In this work, eight predominant strains isolated from spontaneous fermentations in four Tuscan wineries were characterized by technological traits of oenological relevance and laboratory-scale fermentations of both a synthetic must and Sangiovese grape must. In each must, the strains reached similar final ethanol concentrations, although lag phase and maximum fermentation rate differed significantly, whereas the resulting wines differed significantly in glycerol, acetic acid and phenolic alcohol content and in the scores assigned by a trained sensory panel. Four strains spanning the observed range of behaviors were hence analyzed by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight Mass Spectrometry (MALDI-ToF MS) at an early and a mid-fermentation stage, yielding 30–46 differentially abundant proteins identified per strain. Strain-specific abundance of proteins involved in glycerol formation, acetaldehyde oxidation and sulfur amino acid metabolism paralleled the corresponding differences in glycerol, acetic acid and hydrogen sulfide production, whereas glycolytic enzyme abundance varied without any corresponding variation in ethanol. Proteomic analysis thus identified candidate molecular correlates of the traits that distinguish strains, suggesting that it could complement traditional screening in the selection of indigenous starter cultures.