Fractional study of alkali-soluble hemicelluloses obtained by graded ethanol precipitation from sugar cane bagasse.
The two hemicellulosic fractions were subsequentially extracted with 5% and 8% NaOH aqueous solution at a solid to liquid ratio of 1:25 (g mL(-1)) at 50 degrees C for 3 h from the water, 1 and 3% NaOH-treated sugar cane bagasse, and subfractionated into six preparations by a graded ethanol precipitation method at concentrations of 15%, 30% and 60% (v/v). Sugar composition and molecular weight analysis showed that, with an increasing concentration of ethanol, hemicellulosic subfractions with both higher Ara/Xyl ratios and higher molecular weights were obtained. In other words, with an increasing ethanol concentration from 15% to 60%, the Ara/Xyl ratios increased from 0.043 in H(1) to 0.088 in H(3) and from 0.040 in H(4) to 0.088 in H(6), and the weight-average molecular weights of hemicellulosic subfractions increased from 42 430 (H(1)) to 85 510 (H(3)) g mol(-1) and from 46 130 (H(4)) to 64 070 (H(6)) g mol(-1), respectively. The results obtained by the analysis of Fourier transform infrared, sugar composition, and (1)H and (13)C nuclear magnetic spectroscopy showed that the alkali-soluble hemicelluloses had a backbone of xylose residues with a beta-(1-->4)-linkage and were branched mainly through arabinofuranosyl units at C-2 and/or C-3 of the main chain, whereas the differences may occur in the distribution of branches along the xylan backbone.
Peng
Feng
F
State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, China.
Ren
Jun-Li
JL
Xu
Feng
F
Bian
Jing
J
Peng
Pai
P
Sun
Run-Cang
RC
D002482:Cellulose / Q000737:chemistry*; D005591:Chemical Fractionation; D000431:Ethanol / Q000737:chemistry*; D010936:Plant Extracts / Q000737:chemistry / Q000302:isolation & purification; D011134:Polysaccharides / Q000737:chemistry* / Q000302:isolation & purification; D031786:Saccharum / Q000737:chemistry*; D012995:Solubility
D010936:Plant Extracts; D011134:Polysaccharides; D000431:Ethanol; C007916:hemicellulose; D002482:Cellulose; C027433:bagasse