Solution properties of (1-->3)-alpha-D-glucan and its sulfated derivative from Poria cocos mycelia via fermentation tank

Abstract

From Poria cocos mycelia yielded via a pilot scale facility-fermentation tank, a water-insoluble (1-->3)-alpha-D-glucan coded as Pi-PCM3-I was isolated by extraction with 0.5 M NaOH/0.01 M NaBH(4) aqueous solution. Nine fractions from F1 to F9 with a weight-average molecular mass (M(w)) range from 7.75 x 10(4) to 57.3 x 10(4) were prepared from the Pi-PCM3-I sample by a nonsolvent addition method. The fractions were reacted with chlorosulfonic acid-pyridine complex to product water-soluble sulfated derivatives coded as S1 to S8 with M(w) from 2.36 x 10(4) to 14.5 x 10(4) and degree of substitution (DS) of 0.86-1.38. M(w), z-average radius of gyration (s(2) (z) (1/2)), the second virial coefficient (A(2)), and the intrinsic viscosity ([eta]) of the native and sulfated Pi-PCM3-I were measured by laser light scattering (LLS), size-exclusion chromatography combined with LLS (SEC-LLS), and viscometry at 25 degrees C. The Mark-Houwink equations for Pi-PCM3-I in 0.25 M LiCl/dimethylsulfoxide (DMSO) (Me(2)SO) and for its sulfated derivative in 0.15 M NaCl aqueous solution at 25 degrees C were established to be [eta] = 1.33 x 10(-2) M(w) (0.75+/-0.01) (mL g(-1)) and [eta] = 1.46 x 10(-4) M(w) (1.13+/-0.01) (mL g(-1)), respectively. On the basis of theories for a wormlike cylinder model, the conformational parameters of the native and sulfated Pi-PCM3-I were calculated to be 760 +/- 50 and 1060 +/- 30 nm(-1) for the molar mass per unit contour length (M(L)), 6.3 +/- 0.5 and 13.1 +/- 1 nm for the persistence length (q), and 14.9 +/- 0.2 and 31.8 +/- 1 for the characteristic ratio (C( proportional, variant)), respectively. The results revealed that Pi-PCM3-I existed as an extended flexible chain in 0.25 M LiCl/Me(2)SO, and its sulfated derivative existed as a semistiff chain in 0.15 M NaCl aqueous solution. Furthermore, Pi-PCM3-I possessed similar structure and molecular parameters to wc-PCM3-I from a rotary shaker; this suggests promising industrialization of Poria cocos polysaccharides.