An Extracellular Polysaccharide Produced by Zoogloea ramigera 115

A weakly acidic polysaccharide was purified from the extracellular zoogloeal ramigera produced by Zoogloeal ramigera 115. The purified polysaccharide was homogeneous as judged by sedimentation analysis, and the average molecular weight was estimated to be about l0 5 by gel permeation chromatography of the fully methylated preparation. The polysaccharide was composed of d ‐glucose, d ‐gahCtOSe and pyruvic acid in an approximate molar ratio of 11: 3: 1.5. On the basis of methylation, periodate oxidation, Smith degradation and partial hydrolysis, the following highly branched structure was deduced for the polysaccharide : a long chain mainly consisting of β1→4‐linked glucose residues branching at the C‐3 or C‐6 position of galactose residues which are present in β1→4 or β1→ 3 linkages as the minor component of the long chain; pyruvic acid residues, the sole acidic component, are linked to the nonreducing end and/or 1,3‐linked glucose residues through 4,6‐ketal linkages. The purified polysaccharide was not readily soluble in water and had a high affinity for several metallic ions (e.g. 0.25 pmol Fe 3+ /mg, and 0.17 μmol Fe 2+ mg). Upon addition of metallic ions (1 mM) to a gelatinous aqueous solution of the polysaccharide (K + form, 0.125 %), more than 80% of it immediately coprecipitated out with them.