Solution properties of an exopolysaccharide from a Pseudomonas strain obtained using glycerol as sole carbon source

We report the solution properties of a new exopolysaccharide (EPS) obtained from a Pseudomonas strain fed with glycerol as the sole source of carbon. This high molecular mass (3 × 106 g mol−1) biopolymer is essentially made of galactose monomers with pyruvate and succinate groups imparting a polyelectrolyte character. The Smidsrod parameter B computed from the ionic strength dependence of the intrinsic viscosity indicates that the EPS backbone is rather flexible. In salt free aqueous solutions, the zero shear viscosity scaling with concentration follows a typical polyelectrolyte behavior in bad solvent, whereas at high ionic strength the rheological response is reminiscent from neutral polymers. Light scattering data indicate that the EPS adopts a globular conformation as a result of hydrophobic interactions. EPS solutions are stable within 4 days as particle sizing does not indicate EPS aggregation. Both globular conformation and stability against precipitation from solution are attributed to the low charge density of the polyelectrolyte.