Exploring the microbial community, physicochemical properties, metabolic characteristics, and pathways during tank fermentation of Liupao tea

Tank fermentation is a novel fermentation technology; however, the role of microorganisms in Liupao tea quality is unknown. Using high-throughput sequencing, untargeted metabolomics, and targeted absolute quantification, the microbial community, chemical profile, metabolites, and metabolic pathway of Liupao tea were discovered. Sphingomonas, Aquabacterium, Wolbachia, Blastobotrys, Aspergillus, Rasamsonia, and Candida were found to be the most common microorganisms, and throughout fermentation, Blastobotrys was the dominant fungal genus. A total of 40 compounds were identified as differentially changed metabolites (p < 0.05, VIP >1) (VIP: variable important in projection) and significantly contributing to tank fermentation, flavonoids and amino acid derivatives decreased, while nucleotides significantly increased. Gallic acid, EGCG, CG, EGC, EC, etc. could be identified as markers to assess the degree or completion of Liupao tea fermentation. There were significant (p < 0.01) correlations between microbial populations and metabolites, with Sphingomonas being significantly (p < 0.01) associated with 27 metabolites and Blastobotrys being significantly (p < 0.01) associated with 12 metabolites. The metabolic pathways of catechins, flavonoids, and nucleotides elucidate the factors influencing tea quality formation. This research improved our understanding of how Liupao tea processing affects its chemical composition and quality formation.