Structural analysis of an extracellular polysaccharide produced by Rhodococcus rhodochrous strain S-2

A possibility has been suggested of applying the EPS produced by Rhodococcus rhodochrous strain S-2 (S-2 EPS) to the bioremediation of oil-contaminated environments, because its addition, together with minerals, to oil-contaminated seawater resulted in emulsification of the oil, increased the degradation of polyaromatic hydrocarbons (PAH) of the oil, and led to the dominance of PAH-degrading marine bacteria. To understand the underlying principles of these phenomena, we determined the chemical structure of the sugar chain of S-2 EPS. The EPS was found to be composed of d-galactose, d-mannose, d-glucose, and d-glucuronic acid, in a molar ratio of 1:1:1:1. In addition, 0.8% (w/w) of octadecanoic acid and 2.7% (w/w) of hexadecanoic acid were also contained in its structure. By 1H and 13C NMR spectroscopy, including 2D DQF-COSY, TOCSY, HMQC, HMBC, and NOESY experiments, as well as chemical and enzymatic analyses, the polysaccharide was shown to consist of tetrasaccharide repeating units with the following structure:Figure optionsDownload full-size imageDownload as PowerPoint slide

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