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

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.

Keywords: fermentation; kombucha; oxidative stress; rooibos.

Figure 1

The influence of substrate and matrix on bacterial community structure of kombucha (family level), after 14 days of fermentation, as determined by 16S rRNA gene amplicon sequencing, showing in (a) the relative abundance from 0 to 100% and (b) the focus in the range between 98% and 100%.

Figure 2

The influence of matrix (plot) and substrate (only table) on kombucha bacterial community structure after 14 days of fermentation illustrated as a PCoA plot. Bray–Curtis dissimilarity index determined by 16S rRNA gene amplicon sequencing (pairwise ANOSIM, 999 permutations).

Figure 3

The influence of substrate and matrix on bacterial community structure of kombucha (family level) after 7 (a) and 14 (b) days of fermentation, as determined by internal transcribed spacer two (ITS2) gene amplicon sequencing.

Figure 4

The influence of substrate (plot, table), matrix (only table) and fermentation time (only on kombucha fungal community structure after 14 days of fermentation illustrated as a PCoA plot of Bray-Curtis dissimilarity index determined by ITS2 gene amplicon sequencing (pairwise ANOSIM, 999 permutations).

Figure 5

Effects of rooibos kombuchas on L929 cell proliferation; data, expressed as % of control, represent mean ±2 SEM of three independent experiments. Statistical analysis of differences was carried out by two-way ANOVA followed by Fisher’s LSD as post-hoc test. Different letters represent statistical significance (p  ≤  0.05).

Figure 6

L929 cell proliferation after oxidative stress: (a) “Curative model” and (b) “Preventive model”. Data, expressed as % of control, represent mean ±2 SEM of three independent experiments. Statistical analysis of differences was carried out by two-way ANOVA followed by Fisher’s LSD as post-hoc test. Different letters represent statistical significance: (p  ≤  0.05).