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

Abstract

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 ( M w) 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 M w dependences of [ η] and the radius of gyration ( 〈 S 2 〉 z 1 / 2 ) were found to be [ η]=8.9×10 −2 M w 0.57 (cm 3 g −1) and 〈 S 2 〉 z 1 / 2 =4.1×10 −2 M w 0.52 (nm) for GM6-1 in the M w range from 1.50×10 6 to 4.81×10 6, 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 ( M L).