Kombucha beverage is a traditional and popular natural fermented beverage consumed across the globe. Kombucha beverage is produced by fermenting sweetened black tea, sucrose with consortium of acetic acid bacteria and yeasts. It is important to understand the microbial composition in Kombucha to facilitate better control of the fermentation process. Therefore, this study characterized the dominant acetic acid bacteria in Kombucha sample. Acetic acid bacteria isolated from the Kombucha using glucose-ethanol medium. Based on morphological, biochemical characterization, and 16S rRNA gene, 14 isolated strains belong to 2 species and were identified as Komagataeibacter saccharivorans and Komagataeibacter rhaeticus. These strains showed good biofilm forming abilities. Furthermore, the antimicrobial activity against five pathogenic bacteria including Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, Samonella enterica ATCC 13076, Pseudomonas aeruginosa ATCC 27853, Bacillus cereus ATCC 14579 of isolated acetic acid bacteria strains was also determined.  

Strawberries are economically important owing to their unique flavour, health benefits, and nutritional aspects. Decay after harvest is a major issue in the development of strawberry industry. Currently, the most effective method for controlling decay after harvest is storage of strawberries at low temperature combined with usage of chemical fungicides. However, long-term usage of chemical fungicides not only causes pathogen resistance but also is harmful for human health and environment. Biocontrol method for the management of disease after strawberry harvest has great practical significance. In this study, totally 200 bacterial strains isolated from the surface of healthy strawberry fruit were tested for antagonistic activity against five fungal pathogens. Among them, VK199 strain was potent against all five postharvest spoilage fungi on strawberry fruit and then utilized for further study. This strain was identified as Bacillus siamensis based on sequence analysis of 16S rDNA. The extracellular lytic enzymes, including cellulase, amylase, protease and chitinase released by B. siamensis VK199 were detected. Furthemore, in vivo, the results of biological control efficacy test showed that B. siamensis VK199 suppressed the occurrence of diseases caused by Botrytis cinerea, Colletotrichum gloeosporioides, Mucor nidicola and Rhizopus delemar of strawberry during storage.