Characterization of novel bacteriocin PB2 and comprehensive detection of the pediocin gene ped-A1 from Pediococcus pentosaceus PB2 strain isolated from a sorghum-based fermented beverage in Nigeria

Abstract

Lactic acid bacteria (LAB) have been known to possess bacteriocidal activity resulting from ribosomally synthesized antimicrobial peptides called bacteriocin. This study focused on the characterization of the bactericidal activity of bacteriocin PB2 and comprehensive detection of the pediocin ped-A1 from Pediococcus pentosaceus obtained from fermented sorghum beverage, Pito, in Nigeria against Escherichia coli ATCC 25922 and Listeria monocytogenes ATCC 15313. Bacteriocin PB2 was purified in a 2-step purification using 80% NH₄ (SO₄)₂, and Carboxymethyl-Sephadex G-50 column chromatography to achieve a 12.62% purification fold. The physicochemical properties of purified bacteriocin were characterized being treated at different temperatures (20 – 120 °C), pH (2.0 – 10.0), with different detergents and enzymes (sodium dodecyl sulphate (SDS) urea, ox-gall, and proteinase K and RNase A), organic solvents (ethanol, phenol, acetone, chloroform and isoamyl alcohol), and exposure to ultraviolet (UV) radiation (2–12 h) respectively. The molecular weight of the bacteriocin PB2 was determined to be 4.87 kDa. The antibacterial activity of bacteriocin PB2 was optimum at 40 °C and pH 5.0. The bacteriocin PB2 lost its activity on treatment with proteinase K and exposure to UV radiation (after 6 h) but was observed to have stable activity in the presence of organic solvents. Also, P. pentosaceus PB2 harbored two plasmids, 0.9 and 1.2 kb which when cured resulted in the loss of the antimicrobial activity. The mRNA transcript for pedA was detected in P. pentosaceus PB2, but not in the cured derivative, confirming the expression of the plasmid ped-A1 gene in PB2. This study validates our previous study that the PB2 strain of Pediococcus pentosaceus isolated from fermented sorghum, Pito, may be used as a probiotic toward clinically important enteropathogenic bacteria. This peptide is a potential agent for use as an alternative antibacterial agent for the treatment of drug-resistant strains of bacterial infection.