The effect of different yeast and bacterial strain combinations on the physicochemical and metabolic profile of kombucha fermentation

Kombucha is a beverage made by fermenting sweetened black tea with a Symbiotic Culture of Bacteria and Yeast (SCOBY). Most kombucha-related research uses a natural culture for the fermentation process, making it challenging to investigate the specific impacts of different strains on kombucha's fermentation. This study used three strains of acetic acid bacteria (AAB) and three strains of yeast. Three AAB strains (Komagataeibacter saccharivorans LYC1690, Komagataeibacter xylinus LYC1696, Komagataeibacter xylinus LYC1707) and three yeast strains (Zygosaccharomyces bailii LYC1691, Debaryomyces hansenii LYC1262, and Zygosaccharomyces bailii LYC1699) were combined into nine different fermentation processes. This study aims to investigate the impact of acetic acid bacteria and yeast on the fermentation process of kombucha. The investigation involved the determination of parameters, including pH value, acidity, color, total soluble solids, alcohol content, sugar, and organic acids. Principal Component Analysis (PCA) was used to examine metabolic trends. The results showed that yeast strains significantly influenced sucrose consumption, ethanol production, total soluble solids, and organic acid composition. Yeast strain 3 (Z. bailii LYC1699) showed the highest fermentative activity, producing increased ethanol, acetic acid, and malic acid levels while decreasing pH and TSS. In contrast, yeast strain 2 (D. hansenii LYC1262) was associated with increased gluconic and glucuronic acid levels, suggesting potential detoxification benefits. These findings highlight the importance of microbial selection in affecting kombucha's metabolic characteristics to produce novel flavors and functionality.