Production of carbohydrates by the marine diatom Chaetoceros affinis var. willei (Gran) Hustedt. II. Preliminary investigation of the extracellular polysaccharide

The isolation of an extracellular polysaccharide from cultures of Chaetoceros affinis var. willei (Gran) Hustedt is described. The polysaccharide behaved as a homogeneous, polyanionic compound in free-boundary electrophoresis at both pH 2 and 7. It contained sulphur, presumably as sulphate half ester groups (8.7% of SO₂Na), and the following monosaccharides were tentatively identified: rhamnose, fucose, arabinose, and galactose, with the two former constituting 63% of the polysaccharide preparation. The main cellular polysaccharide was a glucan and could be extracted from the cells by dilute acid. The remaining material gave, after hydrolysis, a complex mixture of monosaccharides with rhamnose as the major component. It is concluded that the extracellular polysaccharide is probably excreted from healthy cells.