Metagenomics analysis of the polymeric and monomeric phenolic dynamic changes related to the indigenous bacteria of black tea spontaneous fermentation

Spontaneous fermentation during black tea production involves several reactions, including the oxidation of phenolic compounds. This process has usually been studied without considering the potential involvement of indigenous tea microorganisms. This work utilised a metagenomic technique targeting bacterial 16S rRNA genes and evaluated the profile of phenolic compounds generated during the production of black tea. The resulting data were used to develop correlational and predictive functional analyses related to bacterial dynamics and the syntheses of various phenolic compounds. In particular, the genera Methylobacterium and Devosia were correlated with gallic acid and quercetin. Concurrently, the genera Sphingomonas, Chryseobacterium and Aureimonas were correlated with kaempferol, theaflavins, thearubigins and theabrownins. These results, supported by predicted functional analysis based on 16S rRNA genes associated with phenolic compounds, indicated that yfiH (polyphenol oxidase) and katG (catalase-peroxidase) are likely the dominant genes of the bacterial community involved in the black tea production process. This research suggests that bacteria could potentially contribute to the production process of black tea.