Polyphenol Bioconversion and Volatile Aroma Production by Meyerozyma sp. C3 Isolated from Kombucha in the Theaflavin-Sucrose Fermentation Model.

This study integrated metagenomic and untargeted metabolomics analysis to characterize differences in kombucha communities and metabolites between black tea-sucrose and theaflavin-sucrose systems. Theaflavins selectively enriched yeasts, particularly Meyerozyma and Lodderomyces, and increased the annotated abundance of carbohydrate-metabolism genes, glycoside hydrolases, and glycosyltransferases. Based on these community-level findings, the newly isolated Meyerozyma sp. C3 was employed to establish a simplified single-strain fermentation model to investigate the biotransformation potential of the enriched yeast taxon. The strain exhibited stable growth and sustained acidification throughout fermentation, with a theaflavin conversion rate of 39.5% after 7 days. Metabolomic analysis revealed substantial changes in oligosaccharides (e.g., maltotriose, raffinose), flavonoids/flavanes (e.g., epigallocatechin gallate, (+)-gallocatechin, (-)-epigallocatechin, and catechin derivatives), and organic acids (e.g., citric and isocitric acid), while volatile profiling identified 2-phenylethanol and 4-ethylphenol as newly dominant aroma compounds after fermentation. These results indicate that a yeast-driven route for theaflavin transformation and flavor formation, supporting targeted strain mining and functional fermented-tea development.