Solution and gel rheology of a new polysaccharide excreted by the bacterium Alteromonas sp. strain 1644.

A new bacterial polysaccharide '1644' is studied in aqueous solutions and in the gel state. The viscometric measurements for dilute and semi-dilute solutions in presence of monovalent salts are usual; however, in presence of divalent cations like Ca2+ an original behaviour is observed, related to intermolecular bonds. For larger polymer concentrations a clear gel is obtained with divalent counterions. This gel exhibits unusual properties compared to other gelling polysaccharides: it is very elastic and resistant because of low crosslinking. The mechanical properties of this gel depend closely on the fraction of divalent ions linked to the polymer and so on thermodynamic parameters.