Structural and physical properties of sanxan polysaccharide from Sphingomonas sanxanigenens.

Sphingomonas sanxanigenens, a new species of the genus Sphingomonas, synthesizes extracellular biopolymer termed sanxan. Sanxan polysaccharide was purified from the fermentation broth by Sephacryl S-400 column chromatography. The molecular weight of sanxan polysaccharide was 408kDa by the method of size-exclusion chromatography combined with laser light scattering. Based on FT-IR, periodate oxidation, Smith degradation, composition analysis and nuclear magnetic resonance experiments, the structure of sanxan polysaccharide was elucidated as follows: The solution of sanxan polysaccharide showed properties of high viscosity and shear-thinning. By cooling hot solutions, sanxan polysaccharide could form elastic thermoreversible gel.