Antimicrobial Activity of Fermented Green Tea Liquid

Green tea kombucha made of sugar and single yeast was investigated for its antimicrobial activity and composition changes during fermentation. Individual and total tea polyphenols, caffeine, sucrose, reducing sugar, total sugar, pH, acetic acid and total acids, ethanol concentration, superoxide dismutase and hexokinase activities, yeast yield and antimicrobial activity were measured systematically at the intervals of 12 to 24 hours of fermentation. Results shown that a 36-hour sample had total growth inhibition on Escherichia coli and Staphylococcus aureus, but almost no effects on Bifidobacterium and Lactobacillus delbrueckii subspecies bulgaricus. In order to see the effects of the main components on the microbial growth, a mixture of tea polyphenols, a mixture of acids and ethanol were tested respectively and showed various degrees of antimicrobial activities which were much less than the activity of the 36-hour kombucha, suggesting that there was a synergy effect among the components.