EXTRACELLULAR POLYSACCHARIDES FROM ANKISTRODESMUS-DENSUS (CHLOROPHYCEAE)

The dissolved extracellular compounds produced by the Chlorococcalean Ankistrodesmus densus Kors. were investigated for their molecular mass es and chemical composition. Gel permeation chromatography showed appa rent relative molecular masses of 2 x 10(6) and 10(4), respectively, f or two distinct fractions, termed A and B. The higher molecular weight fraction (A) contained mainly fucose and 3-O-methylgalactose, whereas galactose, glucose, mannose, and rhamnose were present in smaller amo unts. Methylation analyses showed that the main structural features ar e fucose as a highly branched part of polymer A with substitutions in both position 2 and position 4, the substitutions on one of those posi tions being primarily terminal 3-O-methylgalactose and the other one i nvolved as the linkage of rile main chain of the polymer Because of th e presence of both fucose and 3-O-methylgalactose, this polymer is hig hly hydrophobic. Infraction B, mannose represented more than 60% of th e carbohydrate material present, whereas the remaining part contained rhamnose, fucose, xylose, and glucose in almost equal amounts. 3-O-met hylgalactose and galactose were present as minor elements. Fraction B is basically a mannose-containing polymer in which the mannose units a re either 1-->4 or 1-->2 linked. Traces of glucuronic acid and protein were present in both fractions; neither sulfate nor phosphate was det ected.