Determination of thermodynamic properties of sodium alginate from bacteria and seaweeds in aqueous solutions

Alginates are biopolymers produced by seaweeds as well as by some bacteria like Pseudomonas aeruginosa or Azotobacter vinelandii. They consist of copolymers containing 1,4-beta-D-mannuronate and its 5-epimer a-L-guluronate. Their composition and physical properties depend on the source of the alginate. Different alginates from seaweeds and bacteria have been investigated using analytical ultracentrifugation. The samples were prepared in sodium chloride solution to suppress charge effects of the polymers. From the concentration gradient in equilibrium centrifugation the molar masses and the second virial coefficient are derived. The results obtained by this method are in good agreement with the results of light scattering measurements. The properties of different alginates are compared and discussed.