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.
ABSTRACT
Fermented products, including Ogi-baba and Pito, provide several health benefits, particularly when probiotics are used in the fermentation process. Probiotic microorganisms exert strain-specific health-promoting activities on humans and animals. The objective of this study was to investigate the probiotic potentials of Lactic-acid bacteria (LAB) isolates from indigenous fermented sorghum products (Ogi-baba and Pito). The LAB isolates were screened for potential probiotic properties by antagonistic activity against eight enteropathogenic clinical bacteria isolates (Escherichia coli, Klebsiella sp., Helicobacter pylori, Bacillus sp., Staphylococcus sp., Salmonella sp., Pseudomonas sp. and Listeria monocytogenes) as indicator organisms using the agar well diffusion technique. The organisms were also screened for acidity, bile tolerance, antibiotic susceptibility, production of lactic acid, diacetyl and hydrogen peroxide. ß-galactosidase assay was also done. Genomic DNA was extracted from the two selected LAB isolates; the 16S rRNA were amplified and sequenced. The sequence data were subjected to Basic Local Alignment Search Tool (BLAST) and molecular phylogenetic analyses to identify the isolates. The isolates were identified as strains of Lactobacillus plantarum and Pediococcus pentosaceus. The sequence data for these two isolates were submitted to the Genbank with accession numbers KP883298 and KP883297 respectively. The P. pentosaceus strain (PB2) strain exhibited ß-galactosidase activity as well as L. plantrum strain (OB6). The study revealed exceptional probiotic potentials of two LAB namely Lactobacillus plantarum strain (OB6) and Pediococcus pentosaceus strain (PB2) isolated from fermented sorghum products, Ogi-baba and Pito respectively. Hence, the two LAB strains may be potentially used as probiotic to prevent some enteropathogen-induced gastrointestinal disorders; reduce the incidence of respiratory tract infections and for the management of lactose in intolerance.
