Structure and properties of the exopolysaccharides produced by Pseudomonas mutabilis T6 and P. mutabilis ATCC 31014

This paper presents a study on the purification, primary structure, and rheological properties of exopolysaccharides isolated from cultures of Pseudomonas mutabilis T6 and P. mutabilis ATCC 31014. Both polymers are exopolysaccharides of d-mannose. The mannan isolated from P. mutabilis T6 contains on average about 5% of residual β-d-glucose, in contrast to the mannan from P. mutabilis ATCC 31014, which contained only trace amounts of residual β-d-glucose (less than 1%). Based on the 13C NMR spectra, all of the remaining carbohydrates in the exopolysaccharides occur in the form of pyranose rings. All of the mannose residues have the α configuration at the anomeric carbon atom while the glucose adopts the β configuration. The reaction of both polysaccharide hydrolysates with an optically active alcohol indicates that all of the sugar residues have the d configuration. We found that the main chain of the exopolysaccharide is composed of mannose residues connected through α-(1→6) linkages, of which a large number are substituted on O2 with d-mannose and the remaining are substituted with di- to pentasaccharide fragments. The rheological properties of the exopolysaccharide isolated from P. mutabilis T6 show that its viscosity is over 30 times greater than that of P. mutabilis ATCC 31014.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Both exopolysaccharides are mannose polymers. ► All the sugars have pyranose rings. ► All of the sugar residues have configuration D. ► Both EPS’s are composed of mannose residues bonded α(1→6). ► We found phosphodiester linkages (Man-1-P-6-Man) in the EPS.