Polysaccharides of Chlorella pyrenoidosa

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Abstract
Three polysaccharides, hemicellulose A, hemicellulose B and starch, present in the ratio of 92:1 respectively, have been isolated and purified from the alkali-soluble polysaccharides of Chlorella pyrenoidosa. Hemicellulose A has been shown to be homogeneous by several different criteria and its molecular weight, determined by the ultracentrifuge and end-group assay with sodium[14C]cyanide, is 32,000-35,000. The physicochemical data for hemicellulose A have shown that the molecule is a prolate ellipsoid of revolution with an axial ratio of 15. The composition of hemicellulose A was shown to be galactose (7.0 moles), glucose (1.0 mole), mannose (2.0 moles), arabinose (3.0 moles), xylose (3.0 moles) and rhamnose (5.0 moles). Yeast fermentation of the hydrolysate showed that D-galactose and L-rhamnose were present. The optical rotation and the enzymic hydrolysis of hemicellulose A by cellulse and [beta]-galactosidase indicated the presence of [beta]-linkages. A trisaccharide containing galactose, arabinose and rhamnose was isolated from the acetolysis mixture of hemicellulose A. Periodate oxidation and methylation experiments showed that the molecule of hemicellulose A was branched and that 1[forward arrow]6 linkages were present. Branching occurred on some of the galactose residue and mannose and galactose occurred as terminal units. Hemicellulose B was found to contain glucose, galactose, mannose, arabinose, xylose, rahmnose and an unidentified sugar. Chlorella strach was composed of amylose (7%) and amylopectin. The average chain length was nine glucose units, and links other than 1[forward arrow]4 and 1[forward arrow]6 were possibly present.