The microbial composition and functional roles of different kombucha products in Singapore.

Kombucha is a fermented tea known for its health-enhancing properties owing to the bioactive compounds generated by acetic acid bacteria (AAB) and lactic acid bacteria (LAB). We compared the distribution of AAB and LAB across nine kombucha products in Singapore (Product A to I) using shotgun metagenomics. High prevalence of Komagataeibacter species including Komagataeibacter saccharivorans (82.93% in B), Komagataeibacter xylinus (93.38% in D), and Komagataeibacter rhaeticus (92.20% and 30.62% in G and I) was detected in AAB-dominant kombucha. LAB-dominant kombucha was represented mainly by Bacillus coagulans (~99% in E and F) and Lactobacillus nagelii (~60% in H). Despite differences in bacterial composition, all kombucha harbour pathways involved in the biosynthesis of short-chain fatty acids (SCFAs), amino acids and vitamin B12. Interestingly, "fatty acid and beta-oxidation II (peroxisome)" and "fatty acid and beta-oxidation I" were only present in LAB-dominant kombucha. Further study is required to elucidate the significance of the discrepancies. [ABSTRACT FROM AUTHOR]