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

Abstract

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 Brettanomyces, Hanseniaspora, and Saccharomyces and three strains of Acetobacter and Komagataeibacter 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 Saccharomyces cerevisiae towards higher invertase and fermentative activities.

Microbial Composition of SCOBY Starter Cultures Used by Commercial Kombucha Brewers in North America

“…In the presence of oxygen, Brettanomyces yeasts contribute to acetic acid production [ 89 ] alongside the more obvious contribution from acetic acid bacteria [ 90 , 91 ]. In support of this, Tran et al (2020) observed that Kombucha fermentations performed by co-cultures of Hanseniaspora valbyensis and Komagataeibacter saccharivorans contained less sucrose phosphorylase activity than fermentations performed by Komagataeibacter saccharivorans and Brettanomyces bruxellensis , and were characterized by decreased production of both acetic and lactic acids [ 22 ].…”

“…These dynamic changes are well understood for some fermentations, such as Lambic beer [ 52 , 53 ], wine [ 54 , 55 , 56 ] and cheese [ 57 , 58 ]. Efforts to understand the microbial ecology of Kombucha have revealed a greater degree of apparent interchangeability in dominant yeast and bacterial species [ 22 ]. Better understanding of microbial community assemblies found in Kombucha SCOBY would facilitate further research into drivers of assembly patterns, and their relevance to Kombucha style.…”

“…By contrast, dominant yeast genera appears to be substantially more variable from study to study. Zygosaccharomyces [ 1 , 18 ], Candida [ 14 ], Torulaspora [ 1 ], Pichia [ 19 , 20 ], Brettanomyces [ 4 , 14 , 16 , 21 ], Schizosaccharomyces [ 1 , 19 , 21 ], Hanseniaspora [ 4 ], and Saccharomyces [ 1 , 2 , 18 , 22 ] are some of the genera described as important for Kombucha production. Yeast diversity in liquid and solid phases have observed the same taxa in both, but different patterns of succession during the course of fermentation [ 4 , 17 ].…”

“…Yeast diversity in liquid and solid phases have observed the same taxa in both, but different patterns of succession during the course of fermentation [ 4 , 17 ]. The role of yeasts in Kombucha fermentations is to convert sugars to ethanol which is subsequently utilized by AAB [ 22 ]. Indeed, during in vitro experiments with two known Kombucha organisms, Starmerella bacillaris and Acetobacter syzgii , acetic acid was only detected in co-culture, whereas gluconic acid was detected in A. syzgii monoculture [ 23 ].…”

Yeast Fermentation at Low Temperatures: Adaptation to Changing Environmental Conditions and Formation of Volatile Compounds

“…One study, performed by Tran and co-workers, presented the relationship between acetic acid bacteria (AAB) and yeasts during fermentation of kombucha. They showed that AAB stimulate S. cerevisiae yeast to produce metabolites under oxygen-limited conditions [ 32 ]. Another study, conducted by Tufariello and co-workers, was devoted to the improvement of the sensory profile of Negroamaro red wine at both the laboratory and the industrial scale using an innovative mixed starter formulation ( Saccharomyces cerevisiae NP103, Candida zemplinina 35NC1, and Lactiplantibacillus plantarum LP44).…”