Effects of medium variation and fermentation time on the antioxidant and antimicrobial properties of Kombucha

Kombucha is a traditional fermented drink and has recently gained popularity due to its numerous claims on therapeutic effects. It is prepared by sweetening black tea and fermented using a symbiotic culture of acetic acid bacteria and yeasts known as SCOBY. The drink can also be brewed using different type of tea and carbon sources. An investigation was conducted to characterize the antioxidant and antimicrobial properties of kombucha by variation of carbon sources: white sugar (S), jaggery (J) and Kelulut honey (H) in black tea (BT) and green tea (GT) media over a period of 7, 14, 28 and 60 days. The antioxidant and antimicrobial efficacy were tested post fermentation. All samples shown the highest value of DPPH inhibition for antioxidant activity at 7 days of fermentation but subsequently decreased with longer fermentation time except for the combination of green tea with jaggery (GT+J). Fermentation of green tea with white sugar (GT+S) showed the highest value with 84%. On the other hand, black tea with jaggery (BT+J) showed least DPPH activity, 9%. Fermentation with green tea demonstrated a higher antioxidant activity compared to black tea, whereas fermentation of any tea with jaggery showed the least antioxidant activity in comparison to white sugar and honey. Thus, it can be said that extended periods of fermentation reduce the DPPH inhibition of kombucha and jaggery itself as carbon source shows an interesting property. Antimicrobial activity was tested using disk diffusion method against E. coli, S. aureus, P. aeruginosa, B. subtilis and S. marcescens. The efficacy increases with time of fermentation for all combinations. Combination of black tea with all carbon sources was found to have most antimicrobial activity.