Invitro Inhibition of L.monocytogenes by Bacteriocin Like Substances (BLIS) Produced by Indigenous Lactobacillus plantarum strains

Listeria monocytogenes is a pathogenic bacteria that play an important roles in food industry especially in food spoilage. These bacteria can grow at refrigerated temperature and are responsible for listeriosis outbreak worldwide. A number of lactic Acid Bacteria (LAB) produce bacteriocin which are bioactive peptides active against a number of pathogenic bacteria including Listeria monocytogenes. Application of Lactic acid bacteria (LAB) and their bacteriocins are considered as natural and safe strategies for controlling this disease in cheese and meat products. In this study we evaluated the anti-listerial bacteriocin producing ability of locally isolated L.plantarum strains in invitro conditions.Materials and Methods: Eight L.plantarum strains isolated from dairy products and fermented cereals were identified by Biochemical and 16SrRNA sequencing. The antimicrobial activity of the isolates was evaluated against L.monocytogenes using agar well diffusion assay. The supernatant fluids of the mentioned strains were evaluated under the stress conditions including neutralization of pH, effect of proteolytic enzymes, salt, pH and temperature. Supernatant fluids from three of the strains with potential ability to produce bacteriocin like substance (BLIS) were partially purified by vacuum concentrations, ammonium sulphate precipitation and ion exchange (DEAE cellulose) chromatography and freeze dried.Results: The approximate molecular weight of the antilisterial proteins in the selected L.plantarum strains were of approximately 1.8, 4.5 and 6.7KDA, respectively. The freeze dried fractions were stable at refrigerated temperatures for more than two years while remained active for approximately one week at room temperatures. A synergistic bactericidal effect of these fractions in combination with 2.5% Sodium chloride and 1 Log cfu/ml reduction in L.monocytogenes population were observed within 4 hrs of incubation, at 35°C.Discussion: Local L.plantarum strains exhibit potential antilisterial effect and might be promising for future application as natural and safe biological preservatives in food industry for the control of L.monocytogenes.

کلیدواژه ها:

L.plantarum ، anti-listerial ، bacteriocin like substance (BLIS) ، biological preservative