Two-peptide bacteriocin from Lactobacillus plantarum PMU 33 strain isolated from som-fak, a Thai low salt fermented fsh product

A total of 12,520 lactic acid bacteria (LAB) isolated from fermented fsh products "som-fak" were screened for bacteriocin. One Lactobacillus plantarum PMU33 strain produced bacteriocin that inhibited a large number of Gram-positive bacteria including food borne pathogens, Listeria monocytogenes, Bacillus cereus and Staphylococcus aureus. Biochemical studies revealed that the bacteriocin was heat stable even at autoclaving temperature (121°C for 15 min) and was active over a wide pH range (2-10). The bacteriocin purifed and characterized from the culture supernatant consists of two peptides with the molecular masses of 3222 and 3099 by mass spectrometry analysis. The molecular mass of this two-peptide bacteriocin were nearly identical to that of two-peptide plantaricin W (Plw) which consists of two peptides Plwa and Plwβ. The genes encoding these two peptides amplifed by PCR with Plw gene specifc primer showed identical sequences to Plwa and Plwβ. The bacteriocins and their producing strains isolated from som-fak may fnd application as bio-preservatives in fermented food products.