Investigation of probiotic potential of Leuconostoc sp. and Lactobacillus sp. natural isolates from non-commercial milk and water kefir

Abstract

Non-commercial milk and water kefir grains (from a household in Belgrade, Serbia) were used for isolation of lactic acid bacteria on TSA, MRS and M17 agar. Preliminary identification has been performed according to morphological traits (Gram staining, cells shape and colony characteristics on agar plate). Isolates suspected to lactic acid bacteria were tested for selected physiological and biochemical characteristics. Investigations of potential probiotic properties included antimicrobial activity against three different pathogens, sensitivity to simulated gastrointestinal tract conditions and autoaggregation ability. In total, ten cultures were selected for further analysis, five from each milk and water kefir grains. The morphological and physiological profiles showed that isolated strains belong to genera Lactobacillus and Leuconostoc. There were some differences in their sugar fermentation pattern as well as in their antimicrobial activities, with milk kefir cultures being more potent pathogen inhibitors. In simulated gastrointestinal tract conditions all strains showed high sensitivity towards bile acids, while their growth in low pH and pepsin was good. Two cultures only (one from water kefir grains and one from milk kefir grains) showed good autoaggregation ability. Overall, most isolates exposed good probiotic potential. There are no significant differences between lactic acid bacteria isolated from milk and water kefir grains.