Isolation and fractionation of hemicelluloses by graded ethanol precipitation from Caragana korshinskii.
Caragana korshinskii hemicelluloses were isolated with 10% KOH at 25 degrees C for 10h from the delignified materials. The alkali-extractable hemicelluloses were then successively sub-fractionated by graded precipitation at final ethanol concentrations of 10%, 20%, 30%, 45%, 60%, and 80%, respectively. Neutral sugars and molecular weight analyses of the six hemicellulosic subfractions revealed that the molecular weights and the distribution of branches along the xylan backbone are different among the hemicellulosic fractions obtained in various ethanol concentrations. The less branched hemicelluloses with large molecules were precipitated in lower ethanol percentages, while with the increasing ethanol concentrations, more branched hemicelluloses with low molecular weights were obtained. (1)H and (13)C NMR studies revealed that the hemicellulosic subfraction precipitated at an ethanol concentration of 45% had a backbone of D-xylose residues and were branched mainly through 4-O-methyl-alpha-D-glucopyranosyl units.
Bian
Jing
J
Institute of Biomass Chemistry and Technology, Beijing Forestry University, Beijing, China.
Peng
Feng
F
Peng
Pai
P
Xu
Feng
F
Sun
Run-Cang
RC
D032602:Caragana / Q000737:chemistry*; D011232:Chemical Precipitation; D000431:Ethanol / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D011134:Polysaccharides / Q000737:chemistry* / Q000302:isolation & purification*; D017550:Spectroscopy, Fourier Transform Infrared
D011134:Polysaccharides; D000431:Ethanol; C007916:hemicellulose