ارزيابي فعاليت باكتريوسين توليد شده توسط باكتريهاي اسيدلاكتيك جداسازي شده از فرآورده هاي لبني در محيط in situ

Evaluation of in situ activity of bacteriocin produced by lactic acid bacteria isolated from dairy products

Lactic acid bacteria are widely distributed in the nature. Lactic acid bacteria produce various compounds such as organic acids, diacetyl, hydrogen peroxide and bacteriocin during lactic fermentation. Bacteriocins are antimicrobial proteinaceous compounds that are inhibitory towards sensitive strains. In this study, 28 strains of lactic acid bacteria were isolated from dairy products and were tested for antimicrobial activity. The antagonistic activities were tested by agar spot test. Only 17 strains of lactobacilli were shown to produce a bacteriocin - like substance. For extraction of bacteriocin, a cell free solution was obtained by centrifuging the culture. Zone inhibition of indicator strains including 10 strains of microbial pathogen and 11 strains lactobacillus against supernatant of bacteriocin producing lactobacillus were tested by agar well diffusion assay. The maximum inhibition zone of 20mm diameter was obtained with the extract of strain ch5 on Staphylococcus aureus and the minimum inhibition zone of 1mm was obtained with strain d9 on Enterobacter aerogenese. Maximum activity of bacteriocin was achieved at pH 5.5-6.5 and incubation period of 48h at 25-30 ° C. The antimicrobial activity of bacteriocin in the supernatant of cell culture was stable by catalase treatment but was sensitive to proteolytic enzymes such as pepsin.