Microbial Dynamics between Yeasts and Acetic Acid Bacteria in Kombucha: Impacts on the Chemical Composition of the Beverage

Kombucha is a traditional low-alcoholic beverage made from sugared tea and transformed by a complex microbial consortium including yeasts and acetic acid bacteria (AAB). To study the microbial interactions and their impact on the chemical composition of the beverage, an experimental design with nine couples associating one yeast strain and one AAB strain isolated from original black tea kombucha was set up. Three yeast strains belonging to the genera <i>Brettanomyces</i>, <i>Hanseniaspora</i>, and <i>Saccharomyces</i> and three strains of <i>Acetobacter</i> and <i>Komagataeibacter</i> species were chosen. Monocultures in sugared tea were analyzed to determine their individual microbial behaviors. Then, cultivation of the original kombucha consortium and cocultures in sugared tea were compared to determine the interactive microbial effects during successive phases in open and closed incubation conditions. The results highlight the main impact of yeast metabolism on the product's chemical composition and the secondary impact of bacterial species on the composition in organic acids. The uncovered microbial interactions can be explained by different strategies for the utilization of sucrose. Yeasts and AAB unable to perform efficient sucrose hydrolysis rely on yeasts with high invertase activity to access released monosaccharides. Moreover, the presence of AAB rerouted the metabolism of <i>Saccharomyces</i> <i>cerevisiae</i> towards higher invertase and fermentative activities.