Preparation and structural elucidation of a glucomannogalactan from marine fungus Penicillium commune

The coral-associated fungus Penicillium commune produces an extracellular polysaccharide, FP2-1, when grown in potato dextrose-agar medium. FP2-1 was isolated from the fermented broth using anion-exchange and size-exclusion chromatography, and its structure was elucidated by chemical and spectroscopic analyses, including detailed nuclear magnetic resonance spectroscopy. The results showed that FP2-1 was a glucomannogalactan with a molar ratio of galactose, mannose and glucose of 3.9:1.9:1.0. Structure of FP2-1 may be represented, at an average, as a backbone of (1→2)-linked α-mannopyranose with the every second residue substituted at position 6 by a pentasaccharide branch. The branches consist of four (1→6)-linked β-galactofuranose residues with terminal α-glucopyranose residue attached to the last galactofuranose residue at position 2. FP2-1 was a novel galactofuranose-containing extracellular polysaccharide differing from previously described extracellular polysaccharides.