Characterisation of a novel naturally-modified biogenic calcium carbide-containing exopolysaccharide produced from Pseudomonas aeruginosa strain S16 from soil in Nigeria, West Africa

Abstract

I. K. M. Okorie* and A. A. Ogunjobi

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, that was observed to be effective against two antibiotic-resistant strains, namely Klebsiella pneumoniae and Staphylococcus aureus SO183, in another study. HPLC and MS of the exopolysaccharide, confirmed the presence of glucose, rhamnose, xylose arabinose, D-ribose, galactose, mannose and inositol. The phenol-sulfuric acid method, quantified the carbohydrate sugars concentration, as 0.0060 g/L. SEM showed that the exopolysaccharide possessed a sparsely flaky surface, with globular projections. EDX detected nitrogen (48.00%); carbon (20.10%); phosphorus (12.6%); sodium (8.00%); oxygen (6.00%); calcium (2.30%); chlorine (1.20%); magnesium (0.89%); zinc (0.67%); potassium (0.44%), and manganese (0.33%). FTIR spectroscopy, showed oxygen-manganese-oxygen bonds, and the internal bonds of the following component compounds: magnesium oxide, zinc oxide and calcium carbide. FTIR spectroscopy also showed the following functional groups: carboxyl, imine/oxime, amide/peptide, nitro, halo, and anhydride. The exopolysaccharide produced from Pseudomonas aeruginosa strain S16, is a novel, heteropolysaccharidic, naturally-modified, biogenic calcium carbide-containing, exopolysaccharide. The multiple chemicals in the exopolysaccharide, likely give it the potential for a range of biological activities. From available documented research, this is the first report of an exopolysaccharide naturally modified by biogenic calcium carbide, and sodium, magnesium, potassium, and manganese ions.

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