Structure elucidation of an exopolysaccharide produced by Sphingomonas Sanxanigenens NXO2

Structural elucidation of an exopolysaccharide (EPS) isolated from the fermentation broth of Sphingomonas sanxanigenens was achieved with multiple chromatographic and spectrometric techniques. The EPS was a complex heteropolysaccharide consisting of repeating units of d-glucose, L-guluronic acid, and the unusual 3-O-carboxyethyl hexopyranose (3-O-lactyl hexopyranose) in a molar ratio of 2:1:1. Unambiguous identification of the presence and position of the 3-O-lactyl hexopyranose was accomplished with several methodologies. A repeating tetrasaccharide with four acetyl groups per repeating unit was found. Unambiguous positioning of the substituents could not be made but the primary structure with identification of glycosidic linkages and anomeric configuration was as follows: →4)-β-D-Glcp(1 → 4)-α-3-O-Lt-Hexp-(1 → 3)-β-D-Glcp-(1 → 4)-α-L-GulAp-(1→ The average molar mass with a proposed aggregate of double helixes was 320 kDa following de-esterification. A single polysaccharide chain was 160 kDa (210 repeating units).