Characterisation of a novel manganese-containing exopolysaccharide produced from Pseudomonas aeruginosa strain S16 isolated from soil in a mixed animal farm at Ibadan, Oyo State, Nigeria

Antibiotic resistance, that occurs globally, has led to a reduction in the efficacy of many contemporary conventional antibiotics. The aim of this study was to characterise an exopolysaccharide, produced from Pseudomonas aeruginosa strain S16, accession number OQ734845, observed to be effective against, an identified strain of Klebsiella pneumoniae, at 0.156 g/L, and against Staphylococcus aureus SO183, at 0.260 g/L. Pseudomonas aeruginosa strain S16, was previously isolated from soil, in a mixed animal farm, at Ajibode area, Oyo state, Ibadan, Nigeria, through the pour plate method, before it was identified, through biochemical tests, and molecular studies. High performance liquid chromatography (HPLC), and mass spectrometry (MS), of the exopolysaccharide, revealed monosaccharide moieties of glucose, rhamnose, xylose arabinose, D-ribose, galactose, mannose and inositol and each possessed varying peaks. The phenol-sulfuric acid method, quantified the carbohydrate sugars concentration, as 0.0060 g/L. Scanning electron microscopy (SEM), revealed a sparsely flaky, exopolysaccharide surface, with globular projections. Energy dispersive x-ray spectroscopy (EDX), revealed nitrogen (48.00%), carbon (20.10%), phosphorus (12.60%), sodium (8.00%) and oxygen (6.00%), were the predominant elements in the exopolysaccharide, while manganese (0.33%), was the least predominant. Fourier transform infrared (FTIR) spectroscopy, revealed the presence of carboxyl, imine or oxime, nitro, halo, and anhydride functional groups. The exopolysaccharide, was a modified exopolysaccharide; specifically, a manganese-containing, phosphorylated, nitrogenous, heteropolysaccharide. The manganese, likely conferred on the exopolysaccharide, the potential for a range of biological activities. From available documented research, this is the first time, a manganese-containing exopolysaccharide has been reported.