Kombucha is all of the above.
Kombucha is a beverage produced by the fermentation of sweetened tea by yeast and acetic acid bacteria.
The layer or 'biofilm' floating at the top of the liquid is called a S.C.O.B.Y. It's a dense network of nanocellulose produced by the bacteria, which eventually envelops the entire community; sort of like a microbial, highrise apartment. The name itself, S.C.O.B.Y., is an acronym for Symbiotic Culture/Community/Colony Of Bacteria and Yeast.
The origin of Kombucha can be traced to the Tsin Dynasty of China, 220 BC, where it was known as the Divine Che. Kombucha spread through Asia, including Japan and Korea, and was believed to be an elixir that could cure ‘digestive troubles’, containing 'detoxifying' and 'energizing' qualities. Recently, it reached Eastern Europe via trade routes and subsequently spread to the West. (Dufresne and Farnsworth 2000)
While there have been many grandiose claims about its curative properties, human trials are lacking. Existing studies have suggested that its benefits include increased antioxidants versus tea alone (Jayabalan et al. 2008), hepatoprotective effects (Wang et al. 2014), antibacterial and anti fungal compounds (Battikh et al. 2013), and there have even been efforts to apply the cellulose biofilm for wound dressing (Lin et al. 2013).
The symbiotic partners of Kombucha can vary depending on the geographical location that it was brewed in. (Marsh et al. 2014) The bacteria are dominated by acetic acid bacteria, and are classified as Komagataeibacter xylinus (Yamada et al. 2012), formerly known as Gluconacetobacter xylinus or Acetobacter xylinum.
The yeast species are more variable, and can include many genera, including: Saccharomyces, Zygosaccharomyces, Schizosaccharomyces, Dekkera, Pichia, and Candida, among others (Marsh et al. 2014).
The Aktipis Lab is developing Kombucha as a model system for exploring microbial resource sharing and cooperation. The picture above shows "bad bucha", or sweetened tea without Kombucha starter that appears to be contaminated with some sort of mold. In our lab, we are investigating whether the symbiotic community of yeast and bacteria in Kombucha can help to fight off pathogens that single species of microbes cannot.
Blog post by Alex May
Alex is a Research Technologist in the Aktipis and Maley labs. He uses evolutionary biology and cooperation theory to understand the emergence, maintenance, and breakdown of cooperation. He has studied these ideas in multiple systems, from microbes in biofilms, to legume plants that interact with rhizobial bacteria, to the breakdown of multicellular cooperation in cancer.
References
Dufresne, C., & Farnworth, E. (2000). Tea, Kombucha, and health: a review. Food research international, 33(6), 409-421.
Jayabalan, R., Subathradevi, P., Marimuthu, S., Sathishkumar, M., & Swaminathan, K. (2008). Changes in free-radical scavenging ability of kombucha tea during fermentation. Food Chemistry, 109(1), 227-234.
Wang, Y., Ji, B., Wu, W., Wang, R., Yang, Z., Zhang, D., & Tian, W. (2014). Hepatoprotective effects of kombucha tea: identification of functional strains and quantification of functional components. Journal of the Science of Food and Agriculture, 94(2), 265-272.
Battikh, H., Chaieb, K., Bakhrouf, A., & Ammar, E. (2013). Antibacterial and antifungal activities of black and green kombucha teas. Journal of Food Biochemistry, 37(2), 231-236.
Lin, S. P., Calvar, I. L., Catchmark, J. M., Liu, J. R., Demirci, A., & Cheng, K. C. (2013). Biosynthesis, production and applications of bacterial cellulose. Cellulose, 20(5), 2191-2219.
Marsh, A. J., O'Sullivan, O., Hill, C., Ross, R. P., & Cotter, P. D. (2014). Sequence-based analysis of the bacterial and fungal compositions of multiple kombucha (tea fungus) samples. Food microbiology, 38, 171-178.
Yamada, Y., Yukphan, P., Lan Vu, H. T., Muramatsu, Y., Ochaikul, D., Tanasupawat, S., & Nakagawa, Y. (2012). Description of Komagataeibacter gen. nov., with proposals of new combinations (Acetobacteraceae). The Journal of general and applied microbiology, 58(5), 397-404.
Edited by Athena Aktipis