Arundo donax hemicellulosic subfractions were obtained by extraction with dimethyl sulfoxide (DMSO), saturated Ba(OH)2, and 1.0 M aqueous NaOH, and fractionation with gradient 50% and 80% saturation ammonium sulphate precipitation. The detailed structural characteristics of hemicellulosic subfractions were determined by HPAEC, GPC, FT-IR, and 1D (1H and 13C) and 2D (HSQC) NMR. The results revealed that Arundo donax hemicelluloses had considerable heterogeneity, varying in sugar composition, molecular weight, and structural features. The hemicellulosic subfractions precipitated with the lower saturation level of ammonium sulphate (50%) were lesser substituted hemicelluloses as compared with those subfractions obtained with a higher salt concentration (80%). The hemicellulosic subfractions exhibiting higher molecular weights could be precipitated at the lower concentration of saturated ammonium sulphate. FT-IR and NMR analysis indicated that the highly acetylated hemicelluloses were precipitated at relatively lower concentration of saturated ammonium sulphate (50%), and thus the gradient ammonium sulphate technique can discriminate acetyl and non-acetyl hemicelluloses. The DMSO-soluble hemicelllosic subfraction HD50 precipitated by 50% saturated ammonium sulphate mainly consists of low substituted O-acetyl arabino-4-O-methylglucurono-(1?4)-�-D-xylan, in which  4-O-Me-a-D-GlcpA-(1?2) units was linked at position O-2, Araf residues at O-3, and O-acetyl groups at O-2 or O-3. The DMSO-soluble hemicelllosic subfraction HD80 precipitated by 80% saturated ammonium sulphate is mainly composed of highly substituted arabino-4-O-methylglucuronoxylan and �-D-glucans.

Structure and physicochemical properties of Arundo donax hemicelluloses

243rd National Meeting (2012)

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