The role of tea endophytes in black tea fermentation and their impact on black tea quality remain unclear. We collected fresh leaves of Bixiangzao and Mingfeng tea and processed them into black tea, while testing the biochemical composition of both the fresh leaves and the black tea. We also used high-throughput techniques, such as 16S rRNA, to analyze the dynamic changes in the microbial community structure and function during black tea processing in order to investigate the influence of dominant microorganisms on the quality of black tea formation. Our results showed that bacteria, such as Chryseobacterium and Sphingomonas, and Pleosporales fungi dominated the entire black tea fermentation process. Predicted functional analysis of the bacterial community indicated that glycolysis-related enzymes, pyruvate dehydrogenase, and tricarboxylic acid cycle-related enzymes were significantly elevated during the fermentation stage. Amino acids, soluble sugars, and tea pigment content also increased considerably during fermentation. Pearson’s correlation analysis revealed that the relative bacterial abundance was closely related to the content of tea polyphenols and catechins. This study provides new insights into the changes in microbial communities during the fermentation of black tea and demonstrates understanding of the basic functional microorganisms involved in black tea processing.

Cherries, as high-value horticultural products, have long faced preservation challenges due to their perishable nature and limited postharvest longevity. During storage and transportation, these stone fruits are particularly susceptible to quality deterioration and pathological decay, significantly impacting commercial viability and consumer acceptance. Modified atmosphere preservation (MAP) technology has emerged as the predominant preservation method for cherry storage, recognized for its operational safety, environmental controllability, and technical reliability. This review systematically examines the physiological degradation mechanisms of cherries during storage, identifies critical environmental factors influencing decay patterns, and synthesizes recent advancements in MAP applications. The analysis encompasses technological principles and efficacy evaluations of atmospheric modification, with particular emphasis on how regulated temperature, humidity, and gas composition parameters affect the bioactive compound retention, organoleptic properties, and overall eating quality—crucial factors for enhancing consumer satisfaction and market value. Furthermore, this paper critically addresses current technological limitations, including implementation costs, operational complexity, and environmental sustainability concerns. Finally, it proposes innovative optimization strategies and outlines future development trajectories to advance technological refinement and promote sustainable innovation in terms of cherry preservation methodologies.

Polyphenol oxidase and its isoenzymes are crucial enzymes in the tea tree that catalyze the synthesis of theaflavins. In this study, tea tree polyphenol oxidase was used as the research object, and various protein sequence treatments, such as TrxA fusion tag + N-terminal truncation, were tested for prokaryotic expression through the Escherichia coli expression system. Comparative analyses were conducted on the activities of the different recombinant enzyme proteins on the substrates of tea polyphenol fractions. Additionally, the enzyme with the highest catalytic efficiency on the TFDG substrate was immobilized using polyethylene glycol to investigate the yield of its synthesis of TFDG. Our results demonstrated that after N-terminal truncation and TrxA fusion expression, CsPPO1, CsPPO2, CsPPO3, and CsPPO4 were mostly expressed in the form of inclusion bodies in the cell and exhibited varying degrees of enhancement in substrate activity. Specifically, CsPPO1 exhibited significantly increased activity in EC and ECG, CsPPO2 showed enhanced activity towards ECG and EGCG, and CsPPO2 displayed the highest activity toward TFDG substrates. Homology modeling structural analysis of the polyphenol oxidase isozymes revealed that the active centers of CsPPO1, CsPPO2, and CsPPO3 consisted of double copper ion center structures, while the conserved histidine residues surrounding the active centers formed different catalytic activity centers in different structures. Furthermore, polyethylene glycol immobilization significantly increased the activity recovery of the CsPPO2 enzyme to 74.41%. In summary, our study elucidated that tea tree polyphenol oxidase is expressed as inclusion bodies in prokaryotic expression, and the activity of the recombinant enzyme towards substrates could be enhanced through N-terminal truncation and TrxA fusion expression. Moreover, immobilization treatment of the CsPPO2 enzyme greatly improved enzyme efficiency. These findings offer an important enzymatic basis and theoretical support for the synthesis of theaflavins.

Polyphenol oxidase (PPO) is a metalloproteinase widely present in plant organelles that plays crucial roles in photosynthesis, pest and disease resistance, growth and development, and flower color formation. Due to the high cost and reuse difficulties of plant PPO in applications, immobilization has emerged as a key technology to improve its stability, recyclability, and reusability. Immobilized plant PPO has been widely used in environmental and detection fields. This review examines different immobilization methods and carrier materials for plant PPO and summarizes its applications in wastewater treatment, biosensor detection, food preservation, and theaflavin synthesis. Finally, current challenges and future opportunities for immobilized plant PPO are discussed.