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

Pseudomonas stutzeriAS22, when grown on media containing starch and yeast extract and incubated at 30°C and 200rpm for 24h, was found to produce an acidic and high-molecular mass exopolysaccharide (EPS22). The EPS22 was purified and a yield of 1.3g/l was achieved.The average molecular mass of the EPS22 was determined by high-performance size-exclusion chromatography (HPSEC) and showed an average molecular mass of 9.9×105Da and a polydispersity indexMw/Mn(Mw, weight-average andMn, 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. [ABSTRACT FROM AUTHOR]