Solution properties of water-insoluble polysaccharides from the mycelium of Ganoderma tsugae

Two kinds of water-insoluble polysaccharides (GM5-1 and GM6-1) were isolated from the mycelium of Ganoderma tsugae with 0.5 M NaOH aqueous solution at 25 and 65 °C successively. Their chemical structures were characterized by infrared spectroscopy, gas chromatography and 13C NMR. GM5-1 was composed of (1→3)-α-d-glucan and mannoxylan, while GM6-1 was mainly mannoxylan. The sample GM6-1 was fractionated into five fractions by nonsolvent addition, and their weight-average molecular mass (Mw) and intrinsic viscosity [η] were determined by laser light scattering (LLS), size-exclusion chromatography combined with multi-angle laser light scattering (SEC-LLS) and viscometer in 0.25 M LiCl/DMSO at 30 °C. The Mw dependences of [η] and the radius of gyration (〈S2〉z1/2) were found to be [η]=8.9×10−2Mw0.57 (cm3 g−1) and 〈S2〉z1/2=4.1×10−2Mw0.52 (nm) for GM6-1 in the Mw range from 1.50×106 to 4.81×106, implying a random coil conformations in the solution. Molecular parameters of GM6-1 were calculated on the basis of the wormlike cylinder chain to be 4.2 nm for persistent length (q) and 832 nm−1 for molar mass per unit contour length (ML).