Effect of temperature on the dynamic and steady-shear rheology of a new microbial extracellular polysaccharide produced from glycerol byproduct

The effect of temperature on the dynamic and steady-shear rheology of aqueous solutions of an extracellular polysaccharide produced by microbial fermentation using Pseudomonas oleovorans NRRL B-14682 and glycerol byproduct, was studied. The biopolymer solutions have shown a pseudoplastic fluid behaviour and no gel formation was detected for all temperatures studied. As expected, the steady shear and dynamic parameters decreased with increasing temperature, due to the increase of polymer chain mobility. The EPS solutions were thermorheologically simple and stable, since the theological parameters were successfully superimposed to and arbitrary reference temperature using the Time-Temperature Superposition principle, and the Cox-Merz rule was satisfactorily applied. In addition, the rheological properties were maintained under consecutive oscillatory and steady-state tests at 25 degrees C, after exposing the sample to increasing temperatures up to 80 degrees C. This polymer is a good candidate to be used in industrial processes involving temperature variations, at least in the range from 15 to 80 degrees C. (C) 2009 Elsevier Ltd. All rights reserved.