Characterization of a heat stable anti-listerial bacteriocin produced by vancomycin sensitive Enterococcus faecium isolated from idli batter.

Lactic acid bacteria (LAB) are known to produce various types of bacteriocins, ribosomally synthesized polypeptides, which have antibacterial spectrum against many food borne pathogens. Listeria monocytogenes, a pathogenic bacterium, is of particular concern to the food industry because of its ability to grow even at refrigeration temperatures and its tolerance to preservative agents. Some of the bacteriocins of LAB are known to have anti-listerial property. In the present study, the bacteriocin produced by vancomycin sensitive Enterococcus faecium El and J4 isolated from idli batter samples was characterized. The isolates were found to tolerate high temperatures of 60°C for 15 and 30 min and 70°C for 15 min. The bacteriocin was found to be heat stable and had anti-listerial activity. The bacteriocin did not lost anti-listerial activity when treated at 100°C for 30 min or at 121°C for 15 min. The bacteriocin lost its antimicrobial activity after treating with trypsin, protinase-K, protease and peptidase.