title: Structural characterization of extracellular polysaccharides produced by fungi from the genus Pleurotus.
abstract: The extracellular polysaccharides produced in liquid cultures of the ligninolytic fungi Pleurotus cornucopiae, P. eryngii, P. floridanus, P. ostreatus, P. pulmonarius and P. sajor-caju showed similar composition and structure. They included a minor water-soluble fraction, containing D-glucose, D-mannose, D-galactose and protein (rich in amide- and hydroxyl-containing residues which can be involved in protein-polysaccharide linkages). The structural analysis of this fraction mainly showed alpha-(1-->4)-linked glucose units. The structure of the major fraction (amounting to more than 80% of the total extracellular polysaccharide) was investigated in detail. Its low solubility was attributed to the high M(r). For its characterization a procedure of progressive dissolution and dialysis was set up. The methylation analysis showed that it was a (1-->3)-beta-D-glucan and that approximately 25% of the total units were C-6 branched. This result was confirmed by the intensities of the signals assigned to C-3 and C-6, free and substituted, in 13C-NMR spectra. Additional studies showed linear polysaccharides after one-cycle Smith degradation or after glucan acetolysis. Both results, as well as glucose release after the latter treatment, indicated that the C-6 linked side chains are constituted by single glucose residues, on every second or third unit of the main chain of the (1-->3)-beta-D-glucan.
authors.affiliation: Centro de Investigaciones Biológicas, CSIC, Madrid, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Gutiérrez
authors.forename: A
authors.initials: A
authors.lastname: Prieto
authors.forename: A T
authors.initials: AT
authors.lastname: Martínez
mesh_terms: D002236:Carbohydrate Conformation; D002850:Chromatography, Gel; D005110:Extracellular Space; D005690:Galactose / Q000032:analysis; D005936:Glucans / Q000032:analysis / Q000737:chemistry*; D008031:Lignin / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008358:Mannose / Q000032:analysis; D008745:Methylation; D011124:Polyporaceae / Q000737:chemistry*; D011134:Polysaccharides / Q000032:analysis / Q000737:chemistry* / Q000302:isolation & purification; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D005936:Glucans; D011134:Polysaccharides; D008031:Lignin; D008358:Mannose; D005690:Galactose