Identification and antimicrobial activity of lactic acid bacteria isolated from traditionally produced local cheese

Food safety is very important and food products are supposed to be prepared regarding every possible hazard and risk which may affect human health. Consumers prefer natural and safe food with no chemical additive and loss in nutrition. In this means, use of lactic acid happens to be a natual and preferable preservation method. In this study, traditionally made 15 cheese were used; total 525 isolates was obtained from cheeses.142 lactic acid bacteria isolated from local cheese samples were identified by using biochemical tests. The lactic acid bacteria strains were identified at genus levels as leunoconostoc (10), lactobacillus (47) and enterococcus (44) by biochemical tests. The 71 strains were identified at species levels as E. durans (6), E. faecalis (18), E. faecium (24), E. italicus (2), Lb. brevis (1), Lb. paracasei (2), Lb. plantarum (1), Lc. lactis (3), Leu. lactis (1), Leu. mesenteroides (11), and St. parauberis (2) by MALDI-TOF MS analysis. 10 isolates had antimicrobial activity were obtained from 21 samples of local cheese. Supernatants obtained from lactic acid bacteria strains by centrifuging the 24-48 hour incubated lactic acid bacteria strains. Supernatants were studied for two effect mechanisms. Firstly the total antibacterial effect was observed by using the unprocessed supernatant. Then, bacteriocins were obtained from lactic acid bacteria strains isolated from cheeses sources by partial purification and antimicrobial activity of these bacteriocins against some pathogenic microorganisms (L. monocytogenes ATCC 7644, Staph. aureus ATCC 25923, E. coli O157:H7, C. sakazakii ATCC 29544, B. cereus, S. Typhimurium ATCC 140828) were compared. Disc diffusion method were tested. Bacteriosins produced by isolates identified as E. faecium and E. faecalis demonstrated antibacterial activity against E. coli O157:H7 and S. Typhimurium ATCC 14028. It was found that major antimicrobial effect was due to organic acids produced by these organisms.