Rheological studies of the fucose-rich exopolysaccharide FucoPol

In this work, the solution properties of the bacterial fucose-rich polysaccharide, FucoPol, were studied. The effect of pH (3.5-10.0) and ionic strength (0.02-1.0 M NaCl) on the intrinsic viscosity and steady shear flow were evaluated using a central composite rotatable design of experiments and surface response methodology. FucoPol's intrinsic and apparent viscosities presented a quite low variation under a wide range of pH (3.5-8.0) and ionic strength (0.05-0.50 M NaCl) values. FucoPol produced viscous solutions with shear-thinning behavior at different polymer concentrations (0.2-1.2 wt.%). Flow curves were successfully described by the Cross model. The viscosity of the first Newtonian plateau varied from 0.01 to 2.47 Pa s for polymer concentrations from 0.2 to 1.2 wt.%, and the dependence of the estimated relaxation time with polymer concentration suggests a large degree of interaction between FucoPol molecules. Given the results obtained, FucoPol is proposed as thickening agent for applications in which stability of the apparent viscosity under pH and ionic strength variations is required.