Isolation and Characterization of the Slime from a Cyanobacterium, Microcystis aeruginosa K-3A

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A slime material was isolated from axenic cells of the cyanobacterium, Microcystis aeruginosa K-3A, grown in a synthetic medium. Isolation and purification of the slime material were facilitated by the application of a mild mechanical force followed by specific coagulation with calcium ions. The slime material, of a high degree of purity, was isolated in yields of 7.2% as dry weight and 34.5% as fresh weight from whole cells. The slime gel could immobilize a large volume of water in the native state.
The slime material contained 66.9% (w/w) carbohydrate and 12.8% protein. Chemical analyses showed that the carbohydrate was a heteropolysaccharide containing galacturonic acid, rhamnose and xylose as the major constituents in addition to the sugars, fucose, arabinose, mannose, galactose and glucose. The slime material was insoluble in cold and hot water but soluble in 1 N NaOH. Multivalent metal cations and an acidic pH specifically coagulated the slime material, to form gel.