Pu-erh tea's fermentation process alters its microbial community, with aging significantly impacting raw but not ripened Pu-erh, and toxic metabolites present support brewing customs.

2016 PLOS One The Microbiome and Metabolites in Fermented Pu-erh Tea as Revealed by High-Throughput Sequencing and Quantitative Multiplex Metabolite Analysis Zhang Y, Skaar I, Sulyok M, Liu X, Rao M, et al.

Experimental Study Gut Microbiota Microbiome Pu-Erh Tea

The researchers looked into the microbial communities inherent in Pu-erh tea, a special blend originating from Yunnan, China. The fresh leaves of the tea plant, Camellia sinensis, undergo two types of fermentation- the traditional raw fermentation and the faster, ripened variant. Using high-throughput rDNA-amplicon sequencing, a method to identify and quantify various bacteria and fungi present, they examined both the leaves and both types of Pu-erh tea. The study also explored possible mycotoxins in the tea profiles through quantitative liquid chromatography-tandem mass spectrometry, a technique used to detect and quantify various substances.

Despite observing significant alterations in the fungal and bacterial compositions due to both fermentation processes, the researchers found the aging process to produce noteworthy changes in raw Pu-erh but not in the ripened type. They identified 390 fungal operational taxonomic units (OTUs) and 629 bacterial OTUs in the leaves and teas. Interestingly, despite the difference in the speed and nature of the fermentation processes, ripened and well-aged raw Pu-erh teas exhibited similar microbial communities alien from those observed in young, raw Ph-erh tea. They also found 25 toxic metabolites, primarily of fungal origin, with the most common being patulin and asperglaucide. These facts lend credibility to the Chinese custom of discarding the first preparation of the Pu-erh tea and using the damp tea for subsequent brewing.

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The traditional Chinese medicine diagnosis of Cold and Hot Syndromes based on tongue-coating appearance successfully detects signals in the tongue-coating microbiomes that are indicators of the entire body's status.

2012 Scientific Reports Integrating next-generation sequencing and traditional tongue diagnosis to determine tongue coating microbiome Bai Jiang, Xujun Liang, Yang Chen, Tao Ma, Liyang Liu, Junfeng Li, et al.

Gut Microbiota Microbiome

In summary, by studying the tongue-coating microbiomes of chronic atrophic gastritis patients and healthy controls using next-generation sequencing and bioinformatics analysis, we revealed the possible mechanism underlying the traditional tongue diagnosis and highlighted the potential for using tongue coating microbiome features as biomarkers to reflect the holistic status of the human body, especially in gastrointestinal diseases. The current sample size of this study is still small and further investigations with more samples and complete metagenome sequencing are needed for a comprehensive understanding of the system. The observations described here might provide a new direction for understanding the biological basis of TCM tongue diagnosis and the link between the “geographic tongue” and the human body's health status observed in modern Western medicine.

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