Characterization of flavor compounds and core functional microorganisms during pile fermentation of Liupao tea.

Pile-fermentation improves the flavor of Liupao tea and is influenced by microorganisms. However, the relative contributions of bacteria and fungi remain unclear. Here, we systematically analyzed the dynamics associated with the microbial community, bioactive compounds, and aroma compounds during Liupao tea pile fermentation. Fermentation significantly altered 19 flavor compounds, with day 25 identified as a possible critical transition point. Overall flavor compounds transitioned from bitter and astringent to sweet as fermentation progressed. The bacterial community transitioned from copiotrophic to oligotrophic, showing an initial increase in diversity followed by a decline. Fungal communities were dominated by molds in early stages, then by both molds and yeasts, with diversity gradually decreasing. The core functional bacteria more strongly influenced the flavor of Liupao tea than the core functional fungi. Thus, bacteria play a more dominant role than fungi in shaping Liupao tea flavor, and 25 days of pile fermentation is critical for flavor transformation.