Antimicrobial Action and Biopreservation by Autochthonous Lactic Acid Bacteria of Fish

The purpose of this research was to assess native Lactic Acid Bacteria (LAB) for antimicrobial activities in relation to fish preservation. LAB were isolated from intestine of Oreochromis sp. Listeria monocytogenes, being a big microbial hazard of fresh as well as preserved fish food, was chosen against LAB antimicrobials. In the present study sixteen LAB like isolates from fish intestine were judged for their anti-listeria activities by agar well diffusion assay. Thirteen of them were antagonized Listeria monocytogenes (ATCC 657) by creating inhibition zone in nutrient agar plate. Antagonistic activities with inhibitory zones but not with growth circles clearly marked that inhibition was due to antimicrobials but not for competitive exclusion. LAB like bacteria in different forms like live cells, cell-free supernatant, alkaline cell- free supernatant and heated cell-free supernatant conferred antibacterial activities. No acid and hydrogen peroxide inhibition was reported. Except few, most of the alkaline and catalase treated culture supernatant when being heated to 90oC exhibited strong antagonism against the pathogenic strain. Susceptibility of Listeria monocytogenes to LAB antimicrobials seemed to be caused by both thermostable and thermolabile compounds and could be practiced in fisheries industry for food hygiene and also as biopreservatives.