Purpose: The study was carried out to search for a novel, potent antimicrobial agent, purify it, and determine its physico-chemical characteristics.
Methods : Twenty samples of various fermented food products were screened for beneficial microorganisms that showed potent antimicrobial activity. Identification of the most potent bacterial strain was accomplished using16S rRNA gene sequencing. The antimicrobial compound was purified by cationic exchange resin and C18silica cartridges. The antimicrobial compound purity and approximate molecular weight were determined by running Polyacrylamide gel electrophoresis (PAGE) and the stability at different temperatures, pH values, and treatment with different enzymes was tested.
Results : Out of 1500 tested isolate, an Enterococcus durans OSY-EGY strain, isolated from an Egyptian cheese, was found to produce an antimicrobial compound at pH 4.6, at a concentration of 800 arbitrary units/ml. This compound was the most active against Listeria spp., Lactobacillus spp., Pediococcus spp., and Lactococcus lactis. The antimicrobial compound retained its activity after storage at 4°C for 12 months, heating at 100°C for 80 minutes and 120°C for 25 minutes, treatment with alpha-chymotrypsin, trypsin, carboxypeptidase, aminopeptidase, papain enzymes, and over a pH range from 1.0 to 13.0. The antimicrobial compound was purified by cationic exchange resin and C18 silica cartridges with elution by dimethyl sulfoxide (DMSO), which indicated the compound’s cationic and amphipathic nature. PAGE showed the antimicrobial compound as a single band with molecular weight of approximately 5200 kDa.
Significance: The investigated antimicrobial compound showed unique physico-chemical characteristics and stability to digestive enzymes, heat, and acidic and alkaline pH. These traits make it a good candidate as a food preservative.