Antimicrobial Properties of Green and Black Tea and Kombucha
Date of Award
Restricted Access Thesis
College of Theology, Arts, & Sciences
Math & Science
Mihail Iordanov, Ph.D.
Kombucha is a symbiotic community of bacteria and yeast that is used to ferment sweetened tea and produce a sour, slightly sparkling beverage. The bacterial component of Kombucha is invariant, being composed of a cellulose-producing strain of Gluconobacter. The yeast component of Kombucha is highly variable, with several yeast species identified by different researchers in Kombucha cultures. We demonstrate that the type of tea leaves (black vs. green) affects the morphological appearance, temporal dynamics, and, possibly, the species composition of the yeast component of Kombucha.
Some of the beneficial health effects attributed to tea and Kombucha may be due to antibacterial activities. We demonstrate that both black and green tea (BT and GT) and the products of their respective Kombucha fermentations (BTK and GTK) do indeed display diverse tea-specific antibacterial properties against Aeromonas hydrophila, Bacillus cereus, Bacillus subtilis, Micrococcus luteus, Staphylococcus aureus, Staphylococcus epidermidis, and Mycobacterium smegmatis. GT and GTK generally demonstrated stronger antibacterial activities than BT and BTK. We show that all antibacterial activities of tea and Kombucha are resistant to heat denaturation, arguing against a proteinaceous nature of those activities. Lastly, we demonstrate that the activity of GTK against A. hydrophila and S. aureus, two human pathogens, is not acidic in nature. In light of increasing resistance of bacterial pathogens to common antibiotics, our findings suggest that tea and Kombucha may offer novel antibacterial compounds with potential therapeutic application. Future research will aim at the identification of such compounds.