Exploring the microbial composition and metabolites in dark tea Kombucha: a comparative analysis with green tea Kombucha

Kombucha is typically fermented from green or black tea using symbiotic colonies of bacteria and yeasts (SCOBY), known for its rich bioactive components. However, dark tea kombucha, particularly its nonvolatile metabolites, remains underexplored. This study compares the microbial composition and active components of green tea kombucha (K-GT) with those of a 7-year-old Liupao tea kombucha (K-7LP). Both kombuchas were free of pathogenic bacteria, with K-7LP exhibiting greater bacterial diversity, including beneficial species such as <i>Faecalibacterium prausnitzii</i>, <i>Blautia wexlerae</i>, and <i>Phascolarctobacterium faecium</i>. The dominant fungi in K-GT were <i>Dekkera bruxellensis</i>, whereas K-7LP primarily contained <i>Zygosaccharomyces bailii</i>, accounting for 61.8% in K-GT, and 26.8% in K-7LP. Different metabolites between K-GT and K-7LP included 47 flavonoids, 37 nucleotides and derivatives, 21 phenolic acids, and 14 lipids. Notably, nucleotides such as adenosine, adenosine 5'-monophosphate, and 1,7-dimethylxanthine displayed significant associations with fungi like <i>Aspergillus</i>, <i>Plenodomus</i>, and <i>Dekkera</i>. Overall, compared to one-year-aged Liupao tea, seven-year-aged Liupao tea is a superior substrate for kombucha fermentation. Compared to traditional green tea kombucha, dark tea kombucha emerges as a superior beverage, characterized by its unique sweet taste, beneficial microorganisms, and high bioactivity, offering promising prospects and exploitability for its health benefits.