STRUCTURE AND PHYSICAL-PROPERTIES OF THE EXTRACELLULAR POLYSACCHARIDE PS-P4 PRODUCED BY SPHINGOMONAS-PAUCIMOBILIS P4 (DSM 6418)

A new strain, Sphingomonas paucimobilis P4 (DSM 6418), was found during a screening programme for exopolysaccharide-producing bacteria. The highly viscous fermentation broth yields a polysaccharide (up to 10 kg/m(3)), named PS-P4, and shows thixotropic flow behaviour. In the presence of phosphate ions, PS-P4 forms aqueous gels after heating and cooling at alkaline pH. After isolation and purification of the exopolysaccharide, structural analysis by 1D and 2D H-1 NMR spectroscopy and mass spectrometry was performed. The deacylated exopolysaccharide has the following repeating trisaccharide structure: -->4)-beta-D-Glcp-(1 --> 4)-alpha-L-Rhap-(1 --> 3)-beta-D-Glcp(1 -->. Additionally, the presence of ester-bound acetic acid, D-glyceric acid, and (R)3-hydroxybutyric acid in the native polysaccharide was demonstrated.