Concentration and shear-rate dependence of the viscosity of an exocellular polysaccharide

The viscosity of an exocellular polysaccharide (EPS) produced by the bacterium Lactococcus lactis subsp. cremoris B40 was studied in aqueous solution at an ionic strength of 0.10M. First, the zero-shear viscosity was determined as a function of the concentration. From the data in the low concentration range, the intrinsic viscosity was determined. In addition, the shear-thinning behavior was measured at several concentrations. By combining existing theories, a new equation is proposed that describes and predicts the intrinsic viscosity and the concentration dependence of the (zero-shear) viscosity of B40 EPS solutions from the molar mass and the hydrodynamic radius of the polysaccharide. Based on the Rouse theory, the shear-rate dependence of the viscosity also could be described and predicted from the molecular characteristics, i.e., molar mass and radius of gyration. It is shown that these equations can be applied to all random coil polysaccharides. Copyright 1999 John Wiley & Sons, Inc.