This study presents bacteriocin (antimicrobial compound), produced from Bacillus subtilis isolated from dairy products. The strains from unpasteurized milk that showed the largest zone of growth inhibition against the indicator strain, Micrococcus luteus was selected for the study. The selected strain was identified as Bacillus subtilis based on its morphological, physiological and biochemical characteristics. The antibiotic susceptibility tests for B.subtilis against various antibiotics demonstrated high sensitivity to Tetracycline, Moderate and less sensitivity towards Streptomycin and Chloramphenicol respectively while being resistant to penicillin. Culture filtrate containing bacteriocin showed the nature of its thermostability (up to 100°C), expressed a pH tolerance (2.0-10.0), and emerged resistance towards trypsin and pepsin. Partial purification of bacteriocin was performed using ammonium sulphate precipitation and the dissolved crude antimicrobial material was then purified by passing into a column of Silica gel. In SDS-PAGE analysis, purified bacteriocin isolated from Bacillus subtilis showed the molecular weight to be approximately 3.4 KDa. The isolate Bacteriocin was tested finally for antibacterial activity against E. coli, associated with food borne illnesses. The zone of inhibition clearly proved that bacteriocin has inhibitory effect on the food pathogen E.coli, thus confirming its bactericidal action in food.

Keywords: Bacteriocin, Bacillus subtilis, Micrococcus luteus, E.coli, antibacterial agent