Evaluation of antibacterial activity and pH change in herbal drinks fermented by kombucha culture

Kombucha is unique because of symbiotic culture of bacteria and yeast (SCOBY), which carries out the fermentation process [1]. Traditional kombucha is obtained by fermenting sweetened black tea of Camellia sinensis L. Other plants and fruits (e.g., winter savory, peppermint, elderberry, quince) also can be used for fermentation with kombucha culture [2]. According to the scientific literature, SCOBY contains Acetobacter spp., Gluconobacter spp., Lactobacillus spp., and Dekkera spp., Saccharomyces spp., and others [1]. During fermentation process, various organic acids are formed e.g., acetic, D‐glucuronic, gluconic, lactic, citric, oxalic acids. Possibly due to these acids and low pH the kombucha drink has antimicrobial properties against Staphylococcus aureus, Salmonella typhimurium, Escherichia coli and various other pathogens and may be very healthful to maintain human health [2]. The aim of this study was to evaluate antibacterial activity and pH change of kombucha beverage prepared from different herbs after 1, 2, 3 and 8 weeks of fermentation. Sweetened water infusions from lemon balm (Melissa officinalis L.), nettle (Urtica dioica L.), fireweed (Chamaenerion angustifolium L.), rose hips (Rosa canina L.), Ceylon black tea (Camellia sinensis L.) and their mixture were selected for fermentation process. Antibacterial activity of fermented drinks was determined against gram-positive Bacillus mojavensis and Bacillus megaterium, gram-negative Azotobacter vinelandii using agar well diffusion method [3]. The pH of prepared drinks was determined with the use of a calibrated pH-meter. During 8 weeks of fermentation, the pH values reduced from 7.98±0.01 to 2.07±0.01. The highest and the lowest pH values were found in nettle tea before fermentation and in fireweed kombucha after 8 weeks of fermentation, respectively. Antibacterial activity of kombucha samples ranged from 1.0±0.0 mg/ml to 39.1±0.1 mg/ml [...]Gamtos mokslų fakultetasInstrumentinės analizės APCVytauto Didžiojo universiteta