A novel pentosylmannan arising from the yeast Trichosporon cutaneum

A polysaccharide containing d-mannose, d-xylose, and l-arabinose was formed exocellularly by Trichosporon cutaneum and isolated via the insoluble copper complex formed with Fehling's solution. A Smith degradation gave an α-(1 → 3)-linked mannan, which represents the backbone of the polysaccharide. Some of the (1 → 3)-linked mannose residues are substituted with d-xylopyranosyl, d-mannopyranosyl, and 4-O-α-l-arabinopyranosyl-d-xylopyranosyl units, forming a branched structure. Radioactive tracer experiments show that d-xylose and l-arabinose units arise from glucose via a C-6 decarboxylation mechanism.