Promotion effect of nutrient competition and secreted compounds on ethanol tolerance of Saccharomyces cerevisiae in co-culture with Lactiplantibacillus plantarum.

Saccharomyces cerevisiae serves as a cornerstone microorganism in industrial fermentation, and its production processes frequently involve co-fermentation with companion microbes. Among these, lactic acid bacteria (LAB) are commonly employed in combination with S. cerevisiae for various fermentation applications. Our previous work has demonstrated that co-cultivation with Lactiplantibacillus plantarum confers improved ethanol tolerance on yeast cells. Nevertheless, the precise determinants responsible for this beneficial effect remain incompletely elucidated. In the present study, we performed a sequential factor-exclusion strategy to systematically dissect the specific co-culture-derived elements that contribute to this phenotypic enhancement. Our experimental evidence demonstrated that glucose competition and the secretion of compounds by L. plantarum significantly contributed to the elevated ethanol resistance of yeast, whereas competition for physical space exerted no measurable influence. These observations advance our mechanistic understanding of inter-species dynamics between S. cerevisiae and accompanying microorganisms in fermentation ecosystems.