Co-fermentation of kombucha-derived yeasts and Komagataeibacter hansenii: Effects on polyphenol composition and flavor profiles

Kombucha, a traditionally fermented sweetened tea, develops its characteristic chemistry and flavor through microbial activities. Although the shift from traditional symbiotic culture of bacteria and yeast (SCOBY) to well-defined simplified starters is a commercial necessity, the compositional and aromatic outcomes of co-fermenting key strains derived from SCOBY remain to be elucidated. In this study, the chemical and flavor-related outcomes of defined co-cultures using four different yeast strains paired with Komagataeibacter hansenii , isolated from kombucha, were investigated. The results demonstrated that yeasts were associated with higher levels of esterified catechins (e.g., EGCG), whereas co-cultures with K. hansenii corresponded to increased non-ester catechins (e.g., EGC) and distinct organic acid formation. Additionally, volatile organic compound (VOC) profiles varied markedly among groups, with yeast-containing fermentations showing increased accumulation of specific esters and alcohols. Co-culture fermentations exhibited distinct chemical and flavor-related profiles, with K. hansenii-Saccharomyces cerevisiae yielding the most balanced volatile profile. These findings suggest that the different combinations of yeasts and acetic acid bacteria can effectively influence the phenolic and flavor characteristics of kombucha, offering a basis for the rational design of defined starter cultures for precision fermentation.