Abstract: In order to investigate the bioactive ingredients and microbial diversity in the manufacturing process of Fuzhuan tea from Eucommia ulmoides leaves, we examined the bioactive ingredients content and the microbial community structure in samples collected from different steps of the manufacturing process using several analytic methods and high-throughput sequencing content technology, respectively. Meanwhile, we further performed a correlation analysis between the bioactive ingredients and the microbial community structure. The results showed that in the manufacturing process, the contents of all bioactive ingredients detected presented an overall decreasing trend. Aspergillus was the dominant fungus in the whole manufacturing process and its relative abundance decreased gradually from the raw material to the steaming and shaping stage, and increased rapidly after the beginning of the flowering stage. The relative abundance of Aspergillus reached 95.58% on day 4 of flowering, and was more than 99.99% on day 8 and in all subsequent stages, indicating Aspergillus to be the absolute dominant flora. The bacterial community in the manufacturing process?was abundant, which was subordinated?to?7 phyla and 47 genera, of which the dominant bacteria were Rhodococcus, Ralstonia and Burkholderia-caballeronia-Paraburkholderia. From the raw material to day 8 of the flowering stage, the bacterial community diversity was high, with Ralstonia being the dominant genus. Starting from day 12, the bacterial community diversity decreased and the structure tended to be stable, while the relative abundance of Rhodococcus increased significantly, which was the dominant genus in the late stage of flowering and the maturing stage. The correlation analysis between the bioactive ingredients content and the abundance of the major microbial genera indicated that polysaccharides, free amino acids, polyphenols, chlorogenic acid, geniposide and aucubin content were significantly negatively correlated with the abundance of Aspergillus (P < 0.05), while they were correlated positively with Apiotrichum (P < 0.05). The content of total flavonoids was significantly negatively correlated with the abundance of Aspergillus (P < 0.05) but positively with the abundance of Apiotrichum (P < 0.01). The abundance of Rhodococcus was significantly negatively correlated with the contents of water extract as well as polysaccharides, total flavonoids, free amino acids, polyphenols, chlorogenic acid and geniposide (P < 0.01), but negatively with the contents of geniposidic acid and aucubin (P < 0.05). This study broadens the understanding of the bioactive components and microbial diversity in the manufacturing process of Fuzhuan tea from Eucommia ulmoides leaves, which will provide a basis for the formation and improvement of the quality of Fuzhuan tea from Eucommia ulmoides leaves.

Key words: Eucommia ulmoides leaves; Fuzhuan tea; bioactive ingredients; high-throughput sequencing; microbial diversity