Plantaricin LP84, a broad spectrum heat-stable bacteriocin of Lactobacillus plantarum NCIM 2084 produced in a simple glucose broth medium

Lactobacillus plantarum NCIM 2084 produced an antibacterial substance when grown at 40°C for 36 h in a laboratory medium. The antibacterial substance was active against a wide range of bacteria comprising Gram positive and negative foodborne pathogenic and spoilage bacteria. However, related mesophilic lactobacilli were not inhibited, except for L. amylovorus DSM 20531. The antimicrobial activity was observed between late log and stationary growth phases. The antibacterial substance was partially purified through concentration under vacuum, followed by extraction with methanol and acetone (M–A extract). On fractionation of the M–A extract through Sephadex G-25, the activity was present in an eluant volume of 85 to 100 ml (peak I), indicating an apparent molecular mass of between 1 and 5 kDa and the purification attained was 80-fold. The antimicrobial principle was stable to heat (121°C for 20 min) and catalase, but sensitive to trypsin and chymotrypsin, indicating it to be a bacteriocin. The M–A extract exhibited a bactericidal and lytic effect against Bacillus cereus F 4810 and Escherichia coli D 21. The ability of L. plantarum NCIM 2084 to produce an effective bacteriocin in a simple growth medium is of potential interest in its application as a biopreservative in traditional fermented foods.