PARTIAL CHARACTERIZATION OF BACTERIOCINS PRODUCED BY TWO STRAINS OF LACTIC ACID BACTERIA, ISOLATED FROM TRADITIONAL EGYPTIAN DAIRY PRODUCTS

This study presents the characterization of strains of lactic acid bacteria (LAB) from traditional Egyptian dairy products. 623 isolates of lactic acid bacteria (LAB) were studied for their antimicrobial activity against taxonomically related microorganisms. Selected LAB were identified by PCR method as Enterococcus faecium IM1and Enterococcus hirae IM1. Partial purified enterocin from tested strains showed antimicrobial activity against different indicators such as: Brochothrix thermosphacta DSMZ, Carnobacterium maltaromaticum CIP103135^T, Carnobacterium piscicola S4312, Enterococcus faecalis JH2, Listeria grayi CLIP12518, Listeria innocua, Listeria ivanovii ATCC, Listeria monocytogenes and Vagococcus penaei CIP109914^T but have no effect against Bacillus subtilis, Moellerella wisconsensis, Pseudomonas fluorescens, Salmonella enterica, Salmonella montevideo, Salmonella typhimurium and Serratia liquefaciens CIP103238^T. The inhibitory activity was not due to hydrogen peroxide for Enterococcus hirae IM1, but strain Enterococcus faecium IM1 may excrete diverse antimicrobial compounds such as hydrogen peroxide and bacteriocins. Bacteriocins produced by isolated strains were stable between pH 5 and 8 and stable until 100°C/ 20 min. Tested strains were free from some of virulence determinant genes. They may be useful as starter cultures and co-cultures. Consequently, the selected strains can be applied in fermented dairy foods as efficient biopreservatives cultures.