Abstract
Kombucha is sweetened black tea that is fermented by a symbiosis of bacteria and yeast embedded within a cellulose membrane. It is considered a health drink in many countries because it is a rich source of vitamins and may have other health benefits. It has previously been reported that adding lactic acid bacteria (Lactobacillus) strains to kombucha can enhance its biological functions, but in that study only lactic acid bacteria isolated from kefir grains were tested. There are many other natural sources of lactic acid bacteria. In this study, we examined the effects of lactic acid bacteria from various fermented Vietnamese food sources (pickled cabbage, kefir and kombucha) on kombucha’s three main biological functions: glucuronic acid production, antibacterial activity and antioxidant ability. Glucuronic acid production was determined by high-performance liquid chromatography–mass spectrometry, antibacterial activity was assessed by the agar-well diffusion method and antioxidant ability was evaluated by determining the 2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity. Four strains of food-borne pathogenic bacteria were used in our antibacterial experiments: Listeria monocytogenes ATCC 19111, Escherichia coli ATCC 8739, Salmonella typhimurium ATCC 14028 and Bacillus cereus ATCC 11778. Our findings showed that lactic acid bacteria strains isolated from kefir are superior to those from other sources for improving glucuronic acid production and enhancing the antibacterial and antioxidant activities of kombucha. This study illustrates the potential of Lactobacillus casei and Lactobacillus plantarum isolated from kefir as biosupplements for enhancing the bioactivities of kombucha.
Highlights
Lactic acid bacteria (LAB) are important microbes that have long been used in both traditional and modern industrial food fermentation
As well as adding flavor, many food products fermented by LAB are believed to convey health benefits (Dufresne and Farnworth 2000)
One report investigated the interaction between LAB from kefir milk and acetic acid bacteria (AAB) from KBC with respect to growth rate, biomass and secondary metabolites
Summary
Lactic acid bacteria (LAB) are important microbes that have long been used in both traditional and modern industrial food fermentation. As well as adding flavor, many food products fermented by LAB (e.g. yogurt, cheese, pickled cabbage and kefir milk) are believed to convey health benefits (Dufresne and Farnworth 2000). These proposed health benefits include stimulation of the human immune system and antimicrobial activity. We focused on the significance of Lactobacillus spp. in mixed culture KBC in enhancing its three important biological functions: glucuronic acid (GlcUA) production, antibacterial activity and antioxidant ability. We isolated Lactobacillus strains from kefir, pickled cabbage and KBC, and cultured these with the KBC layer in the sweetened black tea medium. We believe that the results of this study will enable the beverage industry to produce higher quality healthy fermented tea
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