ISOLATION AND IDENTIFICATION OF LACTIC ACID BACTERIA FROM MILK AND FERMENTED MILK SAMPLES AND EVALUATION OF THEIR ANTIMICROBIAL EFFECTS

Abstract

Lactic acid bacteria (LAB) produce some substances that have got antimicrobial activity, such as bacteriocin. They have the potential to be used as an inhibitor against pathogenic microorganisms both in food production and the health sector because they are safe and natural. In this study, 28 LAB were isolated from 15 different milk and fermented milk products (cheese, yogurt) in Afyonkarahisar province. 16S rDNA PCR analyzes were performed for molecular identifications of these isolates. According to 16S rDNA sequence analysis of LAB isolates from milk samples were identifed as Lactobacillus fermentum, Lactococcus lactis, Enterococcus faecium. LAB isolates from cheese samples were identifed as Lactobacillus plantarum, Lactobacillus fermentum, Lactobacillus casei, Lactobacillus curvatus, Lactobacillus helveticus, Lactobacillus rhamnosus, Lactococcus lactis, Enterococcus faecalis, Enterococcus faecium. LAB isolates of yogurt samples were identifed as Lactococcus lactis ve Lactococcus garvieae, Enterococcus durans, Lactobacillus fermentum. Agar spot and agar-well diffusion assay method were used to determine the antimicrobial activity of the LAB isolates. LAB of the isolates showed antimicrobial activity at different levels on the tested pathogenic microorganisms. LAB isolates showed higher antimicrobial activity on Klebsiella pneumoniae NRRLB 4420, Pseudomonas aeruginosa ATCC 11778, Listeria monocytogenes ATCC 1911 than Staphylococcus aureus ATCC 25923, Streptococcus faecalis. Also, LAB isolates have lowest antimicrobial effect on E. coli ATCC 35218 and Bacillus subtilis NRS-744.