title: Separation and characterization of acetyl and non-acetyl hemicelluloses of Arundo donax by ammonium sulfate precipitation.
abstract: Delignified  Arundo donax  was sequentially extracted with DMSO, saturated barium hydroxide, and 1.0 M aqueous NaOH solution. The yields of the soluble fractions were 10.2, 6.7, and 10.0% (w/w), respectively, of the dry  Arundo donax  materials. The DMSO-, Ba(OH)(2)- and NaOH-soluble hemicellulosic fractions were further fractionated into two subfractions by gradient 50% and 80% saturation ammonium sulfate precipitation, respectively. Monosaccharide, molecular weight, FT-IR, and 1D ((1)H and (13)C) and 2D (HSQC) NMR analysis revealed the differences in structural characteristics and physicochemical properties among the subfractions. The subfractions precipitated with 50% saturation ammonium sulfate had lower arabinose/xylose and glucuronic acid/xylose ratios but had higher molecular weight than those of the subfractions precipitated by 80% saturation ammonium sulfate. FT-IR and NMR analysis revealed that the highly acetylated DMSO-soluble hemicellulosic subfraction (H(D50)) could be precipitated with a relatively lower concentration of 50% saturated ammonium sulfate, and thus the gradient ammonium sulfate precipitation technique could discriminate acetyl and non-acetyl hemicelluloses. It was found that the DMSO-soluble subfraction H(D50) precipitated by 50% saturated ammonium sulfate mainly consisted of poorly substituted O-acetyl arabino-4-O-methylglucurono xylan with terminal units of arabinose linked on position 3 of xylose, 4-O-methylglucuronic acid residues linked on position 2 of the xylan bone, and the acetyl groups (degree of acetylation, 37%) linked on position 2 or 3. The DMSO-soluble subfraction H(D80) precipitated by 80% saturated ammonium sulfate was mainly composed of highly substituted arabino-4-O-methylglucurono xylan and β-d-glucan.
authors.affiliation: Institute of Biomass Chemistry and Technology, Beijing Forestry University, Beijing, People's Republic of China.
authors.forename: Feng
authors.initials: F
authors.lastname: Peng
authors.forename: Jing
authors.initials: J
authors.lastname: Bian
authors.forename: Pai
authors.initials: P
authors.lastname: Peng
authors.forename: Huan
authors.initials: H
authors.lastname: Xiao
authors.forename: Jun-Li
authors.initials: JL
authors.lastname: Ren
authors.forename: Feng
authors.initials: F
authors.lastname: Xu
authors.forename: Run-Cang
authors.initials: RC
authors.lastname: Sun
mesh_terms: D000645:Ammonium Sulfate; D005590:Fractional Precipitation / Q000379:methods*; D028321:Plant Preparations / Q000737:chemistry* / Q000302:isolation & purification*; D006109:Poaceae / Q000737:chemistry*; D011134:Polysaccharides / Q000737:chemistry* / Q000302:isolation & purification*
chemical_list: D028321:Plant Preparations; D011134:Polysaccharides; C007916:hemicellulose; D000645:Ammonium Sulfate