Use of Response surface methodology to investigate the effect of several fermentation conditions on the antibacterial activity of several kombucha beverages

This study aimed to investigate the effect of sugar concentration and fermentation time on the antibacterial activity of kombucha beverages prepared with four herbal teas. Four types of herbal teas including, black and green tea, lemon verbena, and peppermint were prepared then sweetened with 2, 5, and 8% sugar. The herbal teas inoculated with actively kombucha culture and after 7, 14, and 21 days, the antibacterial activity of the supernatant of beverages was evaluated against four bacteria based on agar well diffusion method. RSM was used to investigate the effect of fermentation time, sugar concentration, and tea type on the antibacterial activity of beverages. Sugar concentration and fermentation time showed a significant effect on the antibacterial activity of beverages-against all tested bacteria and type of herbal tea affected the antibacterial activity of beverages-againstE. coliandS. aureus. Kombucha prepared with black tea at sugar 8% and fermentation time of 21 days showed the most antibacterial activity againstB. cereus.The most antibacterial activity againstS. aureuswas observed in kombucha beverages prepared with green tea and peppermint for fermentation time of 21 days, at 2% and 8% sugar, respectively. Prepared beverages with peppermint and lemon verbena at 8% sugar and 21 days of fermentation showed the most antibacterial activity againstE. coliandS. dysenteriaerespectively. Generally, to achieve the highest antibacterial activity against the tested bacteria recommended preparation of kombucha beverages at the sugar of 8% and fermentation time of 21 days.

Automated summary

This study found that sugar concentration and fermentation time have a significant impact on the antibacterial activity of kombucha beverages. In addition, the type of herbal tea also affects the antibacterial activity of the beverages against specific bacteria. Generally, preparing kombucha beverages with 8% sugar and fermenting for 21 days resulted in the highest antibacterial activity against the tested bacteria.