Kombucha Beverage from Green, Black and Rooibos Teas: A Comparative Study Looking at Microbiology, Chemistry and Antioxidant Activity

TLDR

Kombucha is traditionally produced by fermenting black or green tea with a consortium of acetic acid bacteria and yeasts. This study aimed to compare the microbiology, chemistry, and antioxidant activity of kombucha made from green tea, black tea, and, for the first time, rooibos leaves. The authors fermented each tea with the same starter culture, then assessed microbial diversity in biofilm and kombucha using culture-dependent and culture-independent methods, and quantified polyphenols, flavonoids, ethanol, acids, and antioxidant activity. The kombuchas shared a dominant Komagataeibacter bacterial community, but yeast composition varied by tea type and fermentation stage; rooibos kombucha had low ethanol yet comparable glucuronic acid, and while black and green teas showed higher antioxidant activity, rooibos significantly protected fibroblast cells from oxidative damage, indicating its potential health benefits.

Abstract

Kombucha is usually obtained from the fermentation of black or green tea by a consortium of acetic acid bacteria and yeasts. In this study, kombucha was prepared from the same starter consortium using green and black teas as well as, for the first time, an infusion of rooibos leaves (Aspalathus linearis). Microbial diversity was analysed during fermentation both in the biofilm and in the corresponding kombuchas, using culture-dependent and-independent methods. Polyphenols, flavonoids, ethanol, and acids were quantified and anti-oxidant activities were monitored. All of the Kombuchas showed similarity in bacterial composition, with the dominance of Komagataeibacter spp. Beta diversity showed that the yeast community was significantly different among all tea substrates, between 7 and 14 days of fermentation and between biofilm and kombucha, indicating the influence of the substrate on the fermenting microbiota. Kombucha from rooibos has a low ethanol concentration (1.1 mg/mL), and a glucuronic acid amount that was comparable to black tea. Although antioxidant activity was higher in black and green kombucha compared to rooibos, the latter showed an important effect on the recovery of oxidative damage on fibroblast cell lines against oxidative stress. These results make rooibos leaves interesting for the preparation of a fermented beverage with health benefits.