Wine is a complex product of interactions between yeasts and bacteria, which during the fermentation of grape juice affect the formation of key components. There are various mechanisms of interections between the yeast cells that enable survival as well as faster growth. In order to study interactions between different strains of yeasts we have selected two strains that have a different genetic background, namely the Saccharomyces cerevisiae wine strain and the probiotic strain S. boulardii (nom.nud.). The fermentation of the synthetic must was carried out in a double-stranded membrane fermentor in which cells of different/same strains were separated by the membrane filter. The fermentation dynamics was monitored on the basis of the growth kinetics of the two yeast strains and the consumption of glucose and fructose, and the formation of fermentation products such as ethanol, glycerol. We also monitored the concentrations of organic acids (acetic, citric, tartaric and malic acid). We detected variations in the fermentation dynamics between wine and probiotic yeast, however the dynamics did not change in the combined cultures. The concentrations of the volatile compounds were determined using gas chromatography, such as acetaldehyde and acetic acid, indicated a competitive response between the coupled fermentation strains. The detection of the presence of another yeast strain was determined by the synthesis of signal molecules of 2-phenylethanol, thyrosol, and tryptophol and determined by the expression of the genes responsible for intracellular communication at different stages of fermentation. We have found that the maximum concentration of signal molecules produces wine yeast in a particular culture, while in unified cultures the synthesis of the molecule is regulated by the presence of the second strain. Similarly, expression (ARO, PAU17, THI12) of genes was increased in the presence of another strain.
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