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Journal of Tea Science ›› 2020, Vol. 40 ›› Issue (3): 386-396.doi: 10.13305/j.cnki.jts.2020.03.009

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A Preliminary Study on the Degradation Pathway of Caffeine in Tea Microbial Solid-state Fermentation

ZHENG Chengqin1, MA Cunqiang1,2, ZHANG Zhengyan1, LI Xiaohong1, WU Tingting1, ZHOU Binxing1,*   

  1. 1. Longrun Pu-erh Tea College, Yunnan Agricultural University, Kunming 650201, China;
    2. Kunming Dapu Tea Industry Company Limited, Kunming 650224, China
  • Received:2019-11-26 Revised:2019-12-23 Online:2020-06-15 Published:2020-06-09

Abstract: In order to explore caffeine degradation products and pathways under the action of microorganisms, the dominant strains including Aspergillus sydowii NRRL250, Aspergillus pallidofulvus NRRL4789, Aspergillus sesamicola CBS137324 and Penicillium mangini CBS253.31 were screened and identified during pu-erh tea fermentation. Strains were inoculated into sun-dried green tea leaves for solid-state fermentation. High performance liquid chromatography (HPLC) was used to determine caffeine, theobromine and theophylline contents to explore the effect of microorganisms on caffeine metabolism. UHPLC-QTOF-MS was used for the metabonomic analysis of Aspergillus sydowii inoculated fermentation with sterilization treatment group (ST group) and raw material group (RM group). The results show that the dominant strains such as A. pallidofulvus NRRL4789, A. sesamicola CBS137324 and Penicillium mangini CBS253.31 had no significant effects on the metabolism of caffeine and other purine alkaloids. However, caffeine content was decreased significantly (P<0.05) with a great reduction about 83.89% during the inoculated fermentation of Aspergillus sydowii. Additionally, theophylline content was increased significantly (P<0.05) and arrived to (25.03±1.17) mg·g-1 at the end of fermentation. While theobromine content remained stable. Therefore, Aspergillus sydowii has a profound effect on caffeine degradation metabolism. Nine metabolites related to caffeine degradation were detected by UHPLC-QTOF-MS during the inoculated fermentation, Among them, theophylline, 3-methylxanthine, 1,7-dimethylxanthine and 7-methylxanthine contents were significantly increased (P<0.05) under the action of Aspergillus sydowii which were related to N-demethylation pathway of caffeine and its related metabolites. 1,7-dimethyluric acid and 1-methyluric acid were related to the oxidation pathway of caffeine-related metabolites. It can be seen that Aspergillus sydowii is the dominant strain that can degrade caffeine and has the potential ability to convert caffeine into theophylline. Under the action of spergillus sydowii, both N-demethylation and oxidation were found in caffeine degradation metabolism, and the former was the dominant.

Key words: Pu-erh tea, solid-state fermentation, Aspergillus sydowii, caffeine, degradation pathway

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