The effect of the fermented tea beverage kombucha on the gut microflora

Abstract: Introduction The fermented tea drink kombucha has gained large popularity over the past years. It has been praised for its nutritional content, organic acids and living community of beneficial bacteria. Multiple studies have been conducted on the effect of the nutrients and organic compounds on the body, but none on the effect of the microbial community on the human gut microbiota. That is thus the aim of this study. Materials and methods The study consisted of two parts. Firstly, the microbial community of kombucha was studied by culturing on an array of different media, with different pH and conditions. Colonies were then counted and large ones were randomly selected for sequencing. The second part of the study consisted of a human trial, in which 42 participants consumed either living kombucha, sterilized kombucha of water during a period of three weeks. Fecal samples were collected after a washout period, prior to the trial, at the end of the three weeks and another ten days later. DNA from the samples was extracted, amplified and sequenced using Illumina sequencing. Results The kombucha used for the study was seemingly dominated by yeast, and contained 104-105 CFU/ml. No lactic acid bacteria or Enterobacteriaceae could be cultured. The data collected from the human study did not show an effect of treatment with living or sterilized kombucha. The results did show the composition of the microbial communities of the gut, even though they did not change significantly. Discussion The kombucha shows a low microbial content, below what is recommended as a probiotics dose. Yet the microbes present were hard to culture, and in many cases formed to small colonies to count. This implies that either the concentration is low, or that the result does not reflect the true microbial content due to a large part of the microbes being non-culturable, which has been the case in previous studies. The data obtained from the human study seems sensitive and reliable enough to be able to draw conclusions from. There seem to have been some errors in the handling of the samples, although these are not believed to have affected the results. Conclusion The study found no effect of kombucha on the intestinal flora after three weeks of consumption. In order to improve the analysis of the kombucha itself, molecular methods should be used to analyze the community properly, and culturing conditions optimized to be able to get a better picture of the amount of living microbes.