GE Mengdie, DAI Anran, YANG Chongjing, LIU Jingjing, CHEUNG Chi Keung Peter, CHEN Lei
The edible mushroom Pleurotus tuber-regium (PTR) was fermented to get the mycelium for cell wall component and structure analysis. Several extracted solutions were applied for the isolation of cell wall components, which were then analyzed from aspects of content, chemical composition and structure features. The results indicated that the cell wall structure of PTR mycelium contained four main fractions: an outer fraction of polysaccharide and protein complex which could be extracted using boiling water, an alkali-extractable fraction of heteropolysaccharides (room temperature), a hot alkali-extractable fraction of hyper-branched heteropolysaccharides (80 ℃) and an alkali-insoluble fraction of glucan-chitin complex. The proportions of these four fractions from outer layer to inner layer in PTR cell wall material were calculated to be 2.06:22.06:46.97:18.95. The purified polysaccharide MHA-I, which was obtained from the main component of MHA, was elucidated by the monosaccharide composition and methylation analysis to be composed of T-Xylp, T-Rhap, T-Glcp, 1,3-Glcp, 1,6-Glcp, 1,4-Glcp, 1,3,6-Glcp, 1,4,6-Glcp, 1,3,6-Manp in the molar ratio of 2.01:1.00:27.64:8.19:38.22:20.88:14.38:6.98:3.22 with DB (degree of branching) value of 0.45, the β-glycoside bond in MHA-I was identified by FT-IR. SEC-MALLS analysis revealed that the hyper-branched heteropolysaccharide (MHA-I) had a Mw of 4.502 × 104 g/mol and R.M.S. radius of 33.2 nm. The results of SEM and TEM indicated that the molecular morphology of MHA-I is hyperbranched structure, which existed in torispherical particles in dried powders. The present research could provide a theoretical basis for development and activity of PTR polysaccharides.
