Microbiological Study of Kefir Grains. Isolation and Identification of High Activity Bacteriocin Producing Strains

Microbiological study of seven sorts of home grown kefir grains was carried out in a search of Lactic Acid Bacteria (LAB) strains with antimicrobial activity. Grains were analyzed regarding to their qualitative and quantitative microflora composition, conditions of growth and change of pH of the culture during fermentation. Isolated LAB were tested for antimicrobial activity against Listeria innocua F—bacteria with physiological properties close to these of the food-borne pathogen Listeria monocytogenes, as well as against some other microbial strains of Lactococci and Lactobacilli. A single LAB strain with significant antimicrobial activity against Listeria innocua F (1 638 400 AU/ml) was chosen for further identification and purification of the bacteriocin it produces.