Concentration and shear-rate dependence of the viscosity of an exocellularpolysaccharide

The viscosity of an exocellular polysaccharide (EPS) produced by the bacter ium Lactococcus lactis subsp, cremoris B40 was studied in aqueous solution at an ionic strength of 0.10M. First, the zero-shear viscosity was determin ed as a function of the concentration. From the data in the low concentrati on range, the intrinsic viscosity was determined. In addition, the shear-th inning behavior was measured at several concentrations. By combining existi ng theories, a new equation is proposed that describes and predicts the int rinsic viscosity and the concentration dependence of the (zero-shear) visco sity of B40 EPS solutions from the molar mass and the hydrodynamic radius o f the polysaccharide. Based an the Rouse theory, the shear-rate dependence of the viscosity also could be described and predicted from the molecular c haracteristics, i.e., molar mass and radius of gyration. It is shown that t hese equations can be applied to all random coil polysaccharides. (C) 1999 John Wiley & Sons, Inc.