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Treatment of dewaxed oil palm frond fiber; fast-growing poplar wood; maize stems; and barley, wheat, rice, and rye straws with 2.0% H2O2 at pH 11.6 for 16 hr at 45°C solubilized 85.7%, 49.5%, 78.2%, 79.7%, 87.1%, 92.7%, and 79.4% of the original hemicelluloses and 72.1%, 24.9%, 87.3%, 70.9%, 85.7%, 88.6%, and 89.8% of the original lignin, respectively. The results indicated that hydrogen peroxide at pH 11.6 had a significant effect on the release of hemicelluloses and delignification from oil palm frond fiber and cereal straws such as maize stems and barley, wheat, rice, and rye straws under the condition used. All the hemicellulosic preparations were much lighter in color and had relatively lower amounts of associated lignin than those obtained using traditional alkaline extraction in the absence of peroxide from the corresponding lignified materials. Xylose is the dominant sugar component in the hemicellulosic preparations isolated from oil palm frond fiber, fast-growing poplar wood, maize stems, and barley, wheat and rye straws, whereas the hemicelluloses obtained from rice straw are rich in glucose and xylose. The seven hemicellulosic samples were also studied by fourier transform infrared(FT-IR} and 1H- and 13C-nuclear magnetic resonance(NMR) spectroscopy, gel permeation chromatography(GPC), and thermal analysis. [ABSTRACT FROM AUTHOR]

Over 90% of the original hemicelluloses in the cell walls of bagasse were sequentially extracted with distilled water, 0.5 M NaOH, 0.5, 1.0, 1.5, 2.0 and 3.0% H2O2 at pH 11.5, and 2.0 M NaOH at 55 °C for 2 h. Meanwhile, the successive treatments also released 89.0% of the original lignin. Chemical composition, physico-chemical properties, and structures of the eight hemicelluloses were elucidated by a combination of sugar analysis, nitrobenzene oxidation of bound lignin, molecular determination, Fourier transform infrared, and 1H and 13C NMR spectroscopy and thermal analysis and the results are reported. The results showed that the sequential treatments were very effective on the fractionation of hemicelluloses from bagasse, and the extraction strength, such as alkali and H2O2 concentration, had a great influence on the chemical and structural features of the hemicelluloses, e.g. content of associated lignin and molecular weight. The hemicellulosic fraction, isolated with 0.5% H2O2 at pH 11.5 for 2 h under 55 °C, had a backbone of xylose residues with β-(1→4) linkages and were branched mainly through arabinofuranosyl and 4-O-methyl glucopyranosyl units. Ferulic and p-coumaric acids were found to be esterified to the hemicelluloses. [Copyright &y& Elsevier]

Eight hemicellulosic fractions were obtained by sequential treatment of dewaxed barley straw with 0.1 M NaOH at 45 °C for 3 h, 0.25, 0.5, 1.0, 1.5, 2.0, and 3.0% H2O2 at 45 °C for 3 h at pH 11.5, and 10% KOH–1% Na2B4O7·10H2O at 28 °C for 15 h under continuous agitation. The yields of the fractions were 8.0, 3.1, 3.3, 3.3, 2.2, 2.0, 2.0, and 9.9%, respectively, of the initial amount of barley straw, corresponding to the dissolution of 21.6, 8.4, 8.9, 8.9, 5.9, 5.4, 5.4, and 26.7% of the original hemicelluloses. Meanwhile, the successive treatment also solubilized 29.1, 15.8, 14.6, 10.8, 4.5, 3.2, 2.7, and 3.7% of the original lignin, respectively. This sequential extraction together resulted in dissolution of 91.1% of the original hemicelluloses and 84.8% of the original lignin. The 0.1 M NaOH-soluble hemicellulosic fraction contained mainly xylose, glucose, and arabinose, 44.2, 15.7, and 15.2%, respectively, while the 10% KOH–1% Na2B4O7·10H2O-soluble fraction predominated in xylose, 75.0%. The six alkaline peroxide-soluble fractions were composed of 50.3–54.4% xylose, 14.7–16.9% arabinose, 6.8–10.7% glucose, 6.8–8.5% glucuronic acid or 4-O-methyl-d-glucuronic acid, 0.4–1.5% mannose, and 0.3–1.2% rhamnose. All the hemicellulosic fractions contained substantial amounts of glucuronoarabinoxylans and noticeable quantities of β-glucans. In comparison, the six hemicellulosic fractions, isolated with alkaline peroxide, had much higher molecular weights (56,890–63,810 g mol−1) than those of the two hemicellulosic preparations (28,000–29,080 g mol−1), isolated with alkali in the absence of hydrogen peroxide. The thermal stability of the hemicelluloses increased with an increment of their molar mass. [Copyright &y& Elsevier]