Elevated abundance of Komagataeibacter results in a lower pH in kombucha production; insights from microbiomic and chemical analyses.

Kombucha consumption has grown rapidly worldwide in the last decade, with production at both small- and large scales. The complex fermentation process involves both bacterial and yeast species, but little is known regarding the progression of microbial development during production. We explored the microbial diversity of multiple batches across two kombucha types, i. e commercial scale versus laboratory-made (hereafter "home") kombucha brew using metabarcoding to characterize both fungal and bacterial communities. We found the microbial community of the commercial kombucha brew to be more complex than that of the home brew. Furthermore, PERMANOVA uncovered significant compositional differences between the bacterial ( F  = 2.68, R 2  = 0.23, p  = 00.001) and fungal ( F  = 3.18, R 2  = 0.26, p  = 00.006) communities between batches. For the home brew, both alpha and beta diversity analyses revealed no significant differences between all batches and replicates. When the microbial diversity of the home and commercial kombucha types were directly compared, the former had higher proportions of Ammoniphilus and Komagataeibacter . The commercial kombucha on the other hand were high in Anoxybacillus , Methylobacterium and Sphingomonas. For the fungal communities, the most dominant fungal genera detected in both kombucha types were similar. Linear model revealed significant correlations between some microorganisms and the sugars and organic acids assayed in this study. For example, rising glucose levels correlated with an increase in the relative abundance of Komagataeibacter ( F  = 7.115, Adj. R 2  = 0.44, p  = 00.0003). We believe these results contribute towards achieving a better control of the kombucha fermentation process and may assist in targeted product diversification.