Wheat Straw Hemicellulose Research Articles

Graft polymerization of acrylonitrile and methyl acrylate onto hemicellulose

AbstractGraft polymerizations of acrylonitrile onto both a commercial larchwood hemicellulose and a purified (low lignin) wheat straw hemicellulose could be initiated by ceric ammonium nitrate. The resulting hemicellulose‐g‐polyacrylonitrile (PAN) copolymers were fractionated by extraction at room temperature with dimethylformamide and dimethylsulfoxide. Fractions were characterized by determining both the wt % PAN in each polymer fraction and the molecular weight of grafted PAN. Saponification of the PAN component of hemicellulose‐g‐PAN gave a water‐dispersible graft copolymer with good thickening properties for water systems. An absorbent polymer, similar to the starch‐based absorbents (Super Slurpers), was produced when saponified hemicellulose‐g‐PAN was isolated by methanol precipitation and then dried. Larchwood hemicellulose was also graft‐polymerized with methyl acrylate using ceric ammonium nitrate initiation, and the hemicellulose‐g‐poly(methyl acrylate) was extrusion‐processed into a tough, leathery plastic. Although ceric ammonium nitrate could be used as an initiator for graft polymerizations onto low‐lignin hemicelluloses, it was inert with crude wheat straw hemicellulose containing 11% lignin. The ferrous sulfate–hydrogen peroxide redox system was used to initiate graft polymerizations onto this high‐lignin material, and properties of the resulting hemicellulose‐g‐poly(methyl acrylate) and saponified hemicellulose‐g‐PAN graft copolymers were evaluated.

Structure of hemicelluloses isolated from Canavalia ensiformis and Triticum aestivum straws

Hemicellulose was extracted from horse bean and wheat straws in a yield of 5 and 9% respectively. The whole hemicellulose was hydrolysed and the molar ratio of the component monosaccharides was determined. Uronic acid, galactose, glucose, arabinose and xylose were found in both hemicelluloses. The molar ratio of the monosaccharides was determined in each of 4 fractions derived from the saccharide. The main fractions (B and C) were partially hydrolysed and an oligosaccharide containing arabinose and xylose (1:1) was isolated from both hemicelluloses. Another oligosaccharide containing xylose and glucose (2:1) was also isolated from wheat straw hemicellulose. Periodate oxidation was carried out on fractions B and C. The formic acid and the consumed periodate were determined. Each hemicellulose was subjected to Smith's degradation. Glycerol, erythrytol and compounds containing xylose and glycerol (1:1), and xylose and erythrytol (1:1) were isolated.

744. The constitution of a wheat-straw hemicellulose

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OLIGOSACCHARIDES OF XYLOSE FROM WHEAT STRAW HEMICELLULOSE

A series of oligosaccharides were prepared by autoclaving wheat straw hemicellulose at 120 °C. in distilled water. The di- to the hepta-saccharide inclusive were shown to be members of the (1 → 4)-β-D-xylopyranose series. The octasaccharide was shown to be doubly branched. Certain aspects of the structure of wheat straw hemicellulose are discussed on the basis of these results.

CRYSTALLINE XYLANS FROM STRAWS

Hemicelluloses, extracted from barley, flax, oat, rye, and wheat straw holo-celluloses, were composed predominantly of anhydro-D-xylose units, with small amounts of L-arabinose and D-glucuronic acid. The hemicelluloses had degrees of polymerization ranging from 55 for oat to 185 for rye and were shown to be linear polysaccharides. Autoclaving in distilled water at 120 °C. yielded crystalline xylans from barley, rye, and wheat straw hemicelluloses. The basic structure of the hemicellulose was maintained in the crystalline xylans, which gave identical X-ray diffraction patterns and had similar, linear structures. The crystallization procedure was found to degrade the hemicellulose, removing D-xylose, L-arabinose, and D-glucuronic acid as components of hydrolytic fragments and leaving a pure xylan one sixth to one third the length of its parent hemicellulose. Depending on uronic acid content, the five hemicelluloses in water gave pH values ranging from 2–5 with consequent variations in resistance to hydrolysis during autoclaving