Antimicrobial Impact forLactococcus lactissubsp.lactisA15 andEnterococcus faeciumA15 Isolated from Some Traditional Egyptian Dairy Products on Some Pathogenic Bacteria

Lactococcus lactis subsp. lactis A15 and Enterococcus faecium A15 had antimicrobial activity against Listeria monocytogenes EGDEe 107776. Bacteriocins produced from isolated strains are stable between pH 5 and 8 and stable also until 100C for 10 min. The amount of bacteriocin produced by Lactococcus lactis subsp. lactis A15 reached to the maximum (2560 AU/mL) at the end of logarithmic phase while Enterococcus faecium A15 was observed in logarithmic phase. PCR results revealed the presence of nisin Z structural gene in Lactococcus lactis subsp. lactis A15 and enterocin B gene for Enterococcus faecium A15. Lactococcus lactis subsp. lactis A15 was free from genes of asa1, gelE, espfm, cylA, efaAfs. Otherwise, Enterococcus faecium A15 did not contain an asal, espfm and cylA genes. Tested strains were sensitive to kanamycin, vancomycin and gentamycin. Tested strains were not able to hydrolyze red blood cells. Practical Applications Nowadays, the addition of bacteriocins and/or bacteriocin-producing lactic acid bacteria (LAB) as natural food preservatives to food products (i.e. cheese and yoghurt) has been considered with the aim of increasing the food safety of these products. Bacteriocins have successfully been used to control Listeria monocytogenes. Lactococcus lactis subsp. lactis A15 could be used as starter culture or co-culture in food system for preventing the growth of Listeria monocytogenes and increasing the safety and shelf-life of dairy products. Enterococcus faecium A15 was able to produce gelatinase but not able to hydrolyze red blood cells. On the other hand, the bacteriocin produced from Enterococcus faecium A15 may find application as bio-preservatives for increasing the shelf-life of Egyptian Dairy products.