Effect of metal cations on the viscosity of a pectin-like capsular polysaccharide from the cyanobacterium Microcystis flos-aquae C3-40

Metal ions have a biphasic effect on the viscosity of the capsular polysaccharide from the cyanobacterium Microcystis flos-aquae C3-40 at ph 7. Viscosity increases proportionately with metal ion concentration until a maximum value is reached, and then decreases at higher ion concentrations. Mono- and divalent metal cations have different effects. Divalent metal ions cause gelation in concentrated capsule suspensions and precipitation in dilute suspensions, but monovalent ions have no such effect.