STRUCTURE OF THE CAPSULAR AND EXTRACELLULAR POLYSACCHARIDES PRODUCED BY THE DESMID SPONDYLOSIUM PANDURIFORME (CHLOROPHYTA)

The filamentous desmid Spondylosium panduriforme (Heimerl) Telling var. panduriforme f. limneticum (West & West) Teiling (Desmidiaceae), strain 072CH-UFCAR, is surrounded by a well-defined, mucilaginous capsule consisting of a capsular polysaccharide (CPS). This microalga also produces an extracellular polysaccharide (EPS), which can be isolated from the culture medium. Analysis of the carbohydrate composition of the two polymers by gas chromatography showed that they were different. Both were composed of galactose, fucose, xylose, arabinose, rhamnose, and glucose but in different amounts. For example, glucuronic acid accounts for 24% of the EPS material but only traces were found in the CPS. Significant differences were also found during methylation analysis. Fucose appeared to have a higher degree of branching in the EPS than in the CPS. These branches were located on C-3 and could be the position for the attachment of the glucuronic acid units in the EPS. The glucuronic acid was present as 1 --> 4-linked and terminal units. A possible explanation for the formation of the EPS is suggested.