The fermentation appears to be init

The fermentation appears to be initiated by osmotolerant
yeasts and is then succeeded and ultimately dominated by acid-tolerant species
(Teoh et al. 2004). The metabolic and ecological interactions occurring during kombucha
fermentation are not well investigated. The yeasts primarily convert sucrose
into glucose and fructose and produce ethanol and carbon dioxide with a preference
to fructose as a substrate. The ethanol is then oxidized by the acetic acid bacteria to
produce acetic acid which in turn is able to stimulate the yeasts to produce ethanol
(Liu et al. 1996). Gluconic acid is produced from glucose by Acetobacter.
Kombucha has gained popularity because of the apparent health benefits resulting
from regular consumption. Stimulation of the immune system, digestion, liver function
improvement, some detoxification activity, and reduction of obesity are examples of
reported health claims. However, until now, there islittle scientific evidence forthe healthpromoting
properties of the kombucha beverage. The detoxifying property of kombucha
was considered by several researchers to be due to the capacity of glucuronic acid to
bind toxin molecules in the liver. However, these days the presence of glucuronic acid in
kombucha has been doubted (Greenwalt et al. 2000). Gluconic acid derivatives may have
been misidentified. In some in vitro studies, antibacterial activity of kombucha against
pathogenic bacteria such as Helicobacter pylori, Staph. aureus, E. coli, and B. cereus
was reported, and this inhibitory effect probably is related to the acetic acid content of
kombucha (Steinkraus et al. 1996, Greenwalt et al. 1998). More research is needed to find
scientific evidence for health effects of this fermented tea and to understand the mechanisms
behind these. There is also a lack of knowledge how the biological activities of
tea components such as catechins interact with compounds specifically produced during
kombucha fermentation, and how the components of the tea are changed by the metabolic
activity of the complex microbial association of kombucha.