Isolation and characterization of hemicelluloses and cellulose from rye straw by alkaline peroxide extraction

Extraction of water-treated rye straw with 2% H2O2 at pH 11.5 for 12 h at 20 degrees C, 30 degrees C, 40 degrees C, 50 degrees C, 60 degrees C, and 70 degrees C, released 44.2-71.9% of the original hemicelluloses and 52.7-87.8% of the original lignin. As a comparison, treatment of the straw with a dilute alkaline solution at pH 11.5 for 12 h at 50 degrees C, in the absence of H2O2 yielded only 7.3% of the original hemicelluloses and 7.4% of the original lignin. Xylose was the predominant sugar constituent in the seven solubilized hemicellulosic preparations, and arabinose, glucose, and galactose were present in small amounts. The hemicellulosic samples were further characterized by Fourier transform infrared (FT-IR), and carbon-13 magnetic resonance spectroscopy (C-13-NMR), gel permeation chromatography (GPC), and nitrobenzene oxidation of the associated lignin, and the results are reported. The most obvious feature was found that the alkaline peroxide treatment of the straw under the conditions used did not affect the overall structure of the hemicelluloses as compared to the hemicelluloses isolated with alkali from delignified rye straw.