Probiotic potential of acetic acid bacteria isolated from kombucha in New Zealand in vitro

Abstract

Kombucha is a fermented tea beverage containing live microorganisms, mostly beneficial strains of yeast and acetic acid bacteria (AAB), but empirical evidence is limited supporting the probiotic potential of kombucha. This study reports the in vitro probiotic potential of 36 AAB strains isolated from three Kombucha samples commercially available in New Zealand. Nine representative AAB strains, belonging to three species (Komagataeibacter rhaeticus, Acetobacter musti and Gluconobacter potus), were examined for their primary probiotic characteristics such as tolerance to bile salts, NaCl, and low pH, and temperature. Three non-cellulose forming strains (A. musti LOAAB1, G. potus LOAAB2 and G. potus GBAAB3) were assayed for their cell surface characteristics such as auto-aggregation, co-aggregation with pathogenic bacteria, and hydrophobicity. Antimicrobial, antioxidant activities and enzymatic activities were also investigated for the strains of interest. Results indicated that nine strains were able to grow under low pH in the presence of bile salts, suggesting their potential to survive in the human gut. Six K. rhaeticus strains produced cellulosic pellicles, a potential source of prebiotics for beneficial bacteria. The three AAB strains LOAAB1, LOAAB2 and GBAAB3 showed promising cell surface characteristics, such as auto-aggregation rates (>80 %), co-aggregation with four pathogenic bacteria (13.24–43.47 %), hydrophobicity (42.12 % to 50.20 %), and antioxidant activities (>90 %). All nine strains tested negative for enzymatic activities (haemolytic, proteolytic, phospholipase, and gelatinase), suggesting that they are safe to consume. Together, these data indicate the potential for the three AAB strains to be further investigated as probiotic sources with more in vivo tests for applications in the food and beverages industry.