Microbial Succession, Functional Dynamics, and Their Relationship with Quality Formation During Ripened Pu-Erh Tea Fermentation

Microorganisms are the core drivers of ripened Pu-erh tea (RpPT) quality formation. However, the mechanisms of the microbiological and flavor chemical changes during the fermentation process remain unclear, which limits the quality control of ripened Pu-erh tea fermentation. A physicochemical analysis revealed that fermentation significantly reduced the contents of water extracts, tea polyphenols, free amino acids, soluble sugars, and most catechins (p < 0.05), while flavonoids and tea pigments were significantly accumulated. Amplicon sequencing revealed that Pantoea and Bacillus were the dominant bacterial genera during the early and late fermentation stages, with maximum relative abundances of 97.89% and 63.66%, respectively. Aspergillus and Thermomyces were the dominant fungal genera, reaching maximum relative abundances of 98.34% and 62.59%, respectively. During fermentation, bacterial diversity initially increased and then declined, whereas fungal diversity dropped sharply and subsequently stabilized. Co-occurrence network analysis indicated that microbial interactions were primarily cooperative, with network complexity gradually diminishing as fermentation progressed. Functional prediction showed enhanced microbial metabolism of amino acids and carbohydrates during the mid-to-late stages. Crucially, the stage-specific microbial communities were significantly correlated with distinct flavor compounds, shaping the final aroma profile of ripened Pu-erh tea. These dynamics explain the variations in tea quality and provide critical insights for optimizing the fermentation process.