Isolation and Identification of Antimicrobial Compounds Producing Lactic Acid Bacteria from Dairy Products of Kermanshah Province, Iran

Probiotics are normal flora of the mouth and digestive tract and have beneficial effects on the health of the consumer by regulating the microflora of the intestine, lowering blood cholesterol, stimulating immune system, improving lactose metabolism and the anti-cancer activities. They are also found in meat, vegetables, and dairy products. Most of probiotic bacteria belong to the Lactic acid bacteria group. Probiotics such as lactobacilli prevent the development of a wide range of human and animal's pathogens through producing antimicrobial compounds.In present study, 83 bacterial strains were isolated from 20 yoghurt samples which were collected from rural area of Kermanshah province, West of Iran. Samples were cultured on MRS agar and incubated at 30oC, in CO2 atmosphere. Gram-positive and catalase negative strains were considered as LAB. The antibacterial activities of these isolates were evaluated against Bacillus subtilis, Bacillus cereus and Escherichia coli, as food-born bacterial models using agar diffusion assay. To reduce antibacterial activity of produced lactic acid by the isolates, the supernatants of their fermentation broth were adjusted at pH 6.The results showed that maximum inhibition activity was belonged to strain 44, 61 and 72. These strains have antimicrobial activity against all tested g+ and g- bacteria. These investigated isolates showed no antibacterial activity on tested starter, including Lactobacillus casei and Lactococcuslactis. 16S rRNA gene analysis of strains 44, 61 and 72 revealed that all three potent LAB are belonged to Enterococcus genus. The results of current study showed that isolated LAB from traditional Kurdish cheeses are able to inhibit the growth of food-born spoilage and pathogenic bacteria. Metabolites of native can be considered as suitable alternatives chemicals with side-effects.