Fermentation characteristics and radical scavenging capacities of ginseng berry kombucha fermented by Saccharomyces cerevisiae and Gluconobacter oxydans

Kombucha is a healthy carbonated beverage made by fermenting tea extracts such as green tea and black tea through symbiotic culture of bacteria and yeast. In this study, fermentation characteristics and radical scavenging activity of ginseng berry kombucha (GBK) by Saccharomyces cerevisiae M-5 and Gluconobacter oxydans were measured. As fermentation time increased, pH decreased and titratable acidity increased. Reducing sugars decreased rapidly on day 3. Alcohol content increased dramatically during this period and then decreased. GBK showed increased radical scavenging activity and increased total flavonoid content on day 18 of fermentation compared to before fermentation. In particular, during GBK fermentation, the content of phenolic compounds such as gallic acid (2.09-fold) and chlorogenic acid (2.11-fold) increased, contributing to antioxidant activity. In addition, the major ginsenosides of GBK were identified as Rg2 (10.1 μg/mg) and Re (6.59 μg/mg), and the content of minor ginsenosides, which are easily absorbed forms, increased 2.19-fold by fermentation. GBK also extended survival in a Drosophila model treated with 15% hydrogen peroxide. GBK also reduced reactive oxygen species (p < 0.001) through upregulation of gene expression of antioxidant enzymes such as catalase (p < 0.001), superoxide dismutase (p < 0.05), and glutathione peroxidase (p < 0.001). Therefore, GBK can be presented as a functional food that inhibits oxidative stress by increasing radical scavenging activity during fermentation.