Viscoelastic properties of aqueous solutions of the phosphopolysaccharide "viilian" from Lactococcus lactis subsp cremoris SBT 0495

The viscoelastic properties of the native and partially purified polysaccharide "viilian", excreted by Lactococcus lactis subspecies cremoris SET 0495, are studied performing dynamic oscillatory and steady shear measurements. Dynamic as well as steady shear measurements suggest that aqueous solutions of viilian behave as an entangled polymer solution but not as a weak gel. The differences in the viscoelastic spectra obtained in the absence and presence of salt indicates that viilian shows the characteristics of a polyelectrolyte. Addition of 0.1 M NaCl to dilute solutions suppresses the electrostatic interactions giving rise to a more fluid-like character. At higher polysaccharide concentrations involvement of specific interactions between the polysaccharide molecules become apparent, by the increase in the lifetime of entanglement junctions, even when electrostatic interactions are suppressed by the presence of salt. The results are considered in relation to the chemical characteristics of viilian. The viscoelastic properties of viilian most resemble the characteristics of the exocellular polysaccharide from Cyanospira capsulata. (C) 1999 Elsevier Science Ltd, All rights reserved.