Document Type : Original Article
Authors
1
Kafrelsheikh University, Faculty of Agriculture, Department of Dairy Sciences, B.P. 33516, Kafrelsheikh, Egypt
2
Agriculture Research Center, Animal Production Research Institute, Department of Dairy Science, Sakha, Kafr El-Sheikh, 33717, Egypt
3
Department of Industrial Biotechnology, Faculty of Agro-Industry, Prince of Songkla University, Hat Yai 90112, Thailand
4
Alexandria University, Faculty of Agriculture - Saba Basha, Department of Food Science, P.O. Box, 21531, Bolkely-Alexandria, Egypt
5
12UR 1268 Biopolymères Interactions Assemblages, Équipe Fonctions et Interactions des Protéines, INRA, 44316 Nantes Cedex 03, France.
Abstract
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 CIP103135T, Carnobacterium piscicola S4312, Enterococcus faecalis JH2, Listeria grayi CLIP12518, Listeria innocua, Listeria ivanovii ATCC, Listeria monocytogenes and Vagococcus penaei CIP109914T but have no effect against Bacillus subtilis, Moellerella wisconsensis, Pseudomonas fluorescens, Salmonella enterica, Salmonella montevideo, Salmonella typhimurium andSerratia liquefaciens CIP103238T. 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 strainswere 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.
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