POLYSACCHARIDES FROM CYANOBACTERIA .2. RHEOLOGY OF AQUEOUS-SOLUTIONS OF AN EXTRACELLULAR POLYSACCHARIDE FROM CYANOSPIRA-CAPSULATA

Solution rheology of an extracellular polysaccharide from the cyanobacterium Cyanospira capsulata has been investigated in water and in aqueous 0·1 m NaCl at 25°C. The study has been carried out within a range of defined experimental conditions aiming at providing both steady-shear and transient rheological behaviour. The behaviour of the polysaccharide solutions is reminiscent of that of concentrated guar for the time-dependent properties alone, while for the rheological effectiveness and for the concentration-dependent properties, similarities with xanthan are found. The whole set of preliminary data are discussed within the framework of molecular viscoelastic theories and some inconsistencies are disclosed. These may be solved eventually when a larger number of data are also obtained on different systems. © 1990.