Antibacterial activity of several kombucha beveragesprepared with different herbal teas and under different fermentationconditions

Background and Aim : Kombucha is a sweet and sour beverage, which is obtained by thefermentation of the sugared tea with a symbiosis of yeast and bacteria, especially the acetic acidbacteria. The metabolic concentration and composition of this beverage depends on several factors,including tea type, sugar concentration and fermentation time. This study aimed at the use ofresponse surface methodology to investigate the effect of several fermentation conditions on theantibacterial activity of several Kombucha beverages, which were prepared using four tea infusionat various fermentation times and with different sugar concentrations.Methods : Four types of tea, including black tea, green tea, lemon verbena and peppermint withthree concentrations of sugar (۲, ۵ and ۸%), were prepared and inoculated with actively growingKombucha culture. After ۷, ۱۴ and ۲۱ days, the antibacterial activity of the supernatant of drinkswas evaluated against four gastrointestinal pathogens including E. coli, S. dysenteriae, S. aureusand B. cereus based on agar well diffusion method. In this study, the Central Composite Design(CCD) was used in Response Surface Methodology (RSM).Results : Results showed that increasing sugar concentration and fermentation time had asignificant effect on antibacterial activity of Kombucha beverages against all tested bacteria(P<۰.۰۰۱). Also, the interaction effect of sugar concentration with tea type in increasing the zoneof inhibition of all bacteria was observed. However, the interaction effect of sugar concentrationwith fermentation time has a significant effect on the antibacterial activity of fermented beveragesagainst S. aureus and S. dysenteriae.Conclusion : To achieve the most antibacterial activity of kombucha beverage against B. cereus,preparation of beverage with black tea at sugar concentration of ۸% and fermentation time of ۲۱days was recommended. The most antibacterial activity against S. aureus was obtained by thepreparation of kombucha beverages with green tea and peppermint with fermentation time of ۲۱days, at the levels of ۲% and ۸% of sugar concentrations respectively. Also, the preparation ofkombucha beverages with peppermint and lemon verbena tea with ۸% sugar concentration and ۲۱days fermentation time was recommended to achieve the highest antibacterial activity against E.coli and S. dysenteriae respectively.

کلیدواژه ها:

Kombucha ، Antibacterial activity ، Sugar concentration ، Fermentation time ، Fermented beverage