Isolation and selection of high activity acetic acid bacteria from shredded green tea Kombucha fermented by some commercial SCOBY

Tóm tắt

Vietnam stands as the seventh-largest tea producer globally, offering a wide variety of commercial tea products. During the production of dry tea, approximately 10% of the annual yield consists of shredded tea, which has low economic value and is typically discarded. This type of tea is an abundant resource for producing fermented beverages such as Kombucha, which is produced by fermentation of sugared tea using a tea fungus. This is a symbiotic colony of bacteria and yeast (SCOBY) that converts sucrose into acetic acid. Among the microorganisms participating in this process, acetic acid bacteria take precedence, playing a pivotal role in organic acid production. In this study, six distinct commercial SCOBYs were cultivated in sugared tea broth, and the resulting fermented broth was utilized to isolate acetic acid bacteria. Ten strains were isolated and subjected to an analysis of their colony morphology and biochemical properties. These bacteria were preliminarily categorized into three genera: Acetobacter, Gluconobacter, and Komagataeibacter. Through screening for fermentation capability on YPGD agar medium supplemented with 5 g/L CaCO3 and 40 mL/L ethanol, Acetobacter sp. LDK-A2 displayed the highest acidogenic ability, with a halo zone diameter ratio of 2.1, which was significantly different from other strains. Phylogenetic tree analysis using the 16S rRNA gene sequence identified that strain LDK-A2 belongs to Acetobacter tropicalis species.