Purification and structural data of a highly substituted exopolysaccharide from Pseudomonas stutzeri AS22

The average molecular mass of the EPS22 was determined by high-performance size-exclusion chromatography (HPSEC) and showed an average molecular mass of 9.9 × 105 Da and a polydispersity index Mw/Mn (Mw, weight-average and Mn, number-average) of 1.197 ± 0.015. Structural data of this EPS22 were determined using a combination approach including monosaccharide composition (HPAEC-PAD and GLC), methylation analysis (GC-MS) and NMR spectroscopy analysis. EPS22 was found to be a complex heteropolysaccharide with a repeating unit mainly composed of glucose, mannose and lactyl rhamnose in a molar ratio of 1:1.1:0.7. The acidic nature of the polysaccharide is due to the presence of three non-osidic substituents consisting of a lactyl, acetyl, and pyruvyl groups.