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Guanine deaminase provides evidence of the increased caffeine content during the piling process of pu'erh tea.

ABSTRACT: Wet piling is a key process for producing pu'erh tea because various components change under the action of microorganisms. Among these components, caffeine content is increased. Evidence has indicated a salvage pathway for caffeine biosynthesis in microbes, in which xanthine is methylated in the order of N-3 → N-1 → N-7. In addition, guanine can be used to synthesize xanthine through guanine deaminase (EC: 3.5.4.3). In this study, we investigated the variation in caffeine content during piling fermentation with supplementary guanine, ¹⁵N-labeled guanine and xanthine. We cloned the guanine deaminase gene (GUD1) from Saccharomyces cerevisiae (one dominant strain in piling fermentation). The results revealed that [¹⁵N]xanthine could be synthesized from [¹⁵N]guanine, and [¹⁵N]caffeine was also detected during piling with supplementary [¹⁵N]xanthine. Furthermore, ScGUD1 could catalyze the conversion of guanine to xanthine, which is likely to be methylated for caffeine synthesis under microorganism action. The obtained results revealed the mechanism underlying the increased caffeine content during piling of pu'erh tea.

SUBMITTER: Pan SA

PROVIDER: S-EPMC9075041 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature

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Guanine deaminase provides evidence of the increased caffeine content during the piling process of pu'erh tea.

Pan Si-An SA Sun Ying Y Li Mengmeng M Deng Wei-Wei WW Zhang Zheng-Zhu ZZ

RSC advances 20191107 62

Wet piling is a key process for producing pu'erh tea because various components change under the action of microorganisms. Among these components, caffeine content is increased. Evidence has indicated a salvage pathway for caffeine biosynthesis in microbes, in which xanthine is methylated in the order of N-3 → N-1 → N-7. In addition, guanine can be used to synthesize xanthine through guanine deaminase (EC: 3.5.4.3). In this study, we investigated the variation in caffeine content during piling f ...[more]

PMID: 35540571

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Project description:PurposePiling is a critical process for the formation of raw Liupao tea (RLT) flavor quality. However, given the unclear changes in the flavor quality of RLT during the piling process, and the key substances of taste-contributing and aroma components that affecting the flavor quality of RLT was lacking. Herein, the present study aimed at evaluating the changes in flavor quality and its key substances of RLT during the piling process.MethodsSensory evaluation was conducted on RLT samples collected at 11 time points during the piling process. The biochemical and aroma components of these samples were detected using UV spectrophotometer, high-performance liquid chromatography (HPLC), and headspace solid-phase microextraction gas chromatography-mass spectrometer (HS-SPME-GC-MS), respectively. Multivariate analysis was performed to investigate the effects of piling time on the flavor quality of RLT.Key findingsThe sensory quality of RLT increased and then decreased during the piling process. The changes in flavor quality of RLT during the piling process could be divided into four stages: 0-6, 9-15, 18-24, and 27-30 h. The flavor quality of RLT changed significantly with the variations in biochemical and volatile compounds. The key contributors to taste changes included significant decreases in (-)-epigallocatechin gallate, (-)-epicatechin gallate, (-)-epigallocatechin, (-)-catechin gallate, and theobromine content and significant increases in gallic acid, gallocatechin, and theaflavin content. Additionally, alterations in the content of 19 characteristic aroma compounds, such as cedrol, methyl salicylate, methyl palmitate, trans-nerolidol, decanal, 6,10-Dimethyl-2-undecanone, neryl alcohol, α-cedrene, and (E, E)-2,4-heptadienal, significantly influenced the aroma of the tea infusion. This study provides insights into the formation of flavor quality in RLT at different piling stages, which also provide a scientific foundation for optimizing the piling and production processes of RLT.

Dataset Information

Guanine deaminase provides evidence of the increased caffeine content during the piling process of pu'erh tea.

Publications

Guanine deaminase provides evidence of the increased caffeine content during the piling process of pu'erh tea.

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