Structural and physico-chemical characterization of hemicelluloses from ultrasound-assisted extractions of partially delignified fast-growing poplar wood through organic solvent and alkaline solutions.
One organic and three alkaline hemicellulosic fractions were isolated by an ultrasound-assisted extraction which partially delignified the fast-growing poplar wood. Successive treatments were conducted with dimethyl sulfoxide under ultrasonic irradiation at 570W, 25 degrees C for 30min, 70% ethanol containing 1% NaOH, 3% NaOH and 6% NaOH at 75 degrees C for 3h, respectively. The four hemicellulosic fractions obtained were comparatively studied by sugar analysis, alkaline nitrobenzene oxidation of bound lignin, GPC, FT-IR, 1D and 2D NMR spectroscopy as well as TGA and DTA. The results showed that the ultrasonic treatment and sequential extractions with three different concentrations of NaOH led to a release of 75.5% of the original hemicelluloses and 96.2% of the lignin. All four purified hemicellulose fractions contained relatively low amounts of associated lignin, ranging between 0.96 and 3.10%. In addition, the hemicellulosic fraction H(4) isolated with 6% NaOH is formed by a linear backbone of four (beta-1-->4)-xylopyranosyl residues and at least one of the xylose residues is monosubstituted at C-2 by a 4-O-methylglucuronic acid, giving a typical ratio of 4-O-methyl glucuronic acid to Xyl of 1 to 4.
Yuan
Tong-Qi
TQ
Institute of Biomass Chemistry and Technology, Beijing Forestry University, Beijing 100083, PR China.
Xu
Feng
F
He
Jing
J
Sun
Run-Cang
RC
D000447:Aldehydes / Q000737:chemistry / Q000378:metabolism; D001709:Biotechnology / Q000379:methods*; D050260:Carbohydrate Metabolism; D002241:Carbohydrates / Q000737:chemistry; D008031:Lignin / Q000737:chemistry* / Q000378:metabolism; D008970:Molecular Weight; D019906:Nuclear Magnetic Resonance, Biomolecular; D010209:Paper; D011134:Polysaccharides / Q000737:chemistry* / Q000378:metabolism; D032107:Populus / Q000737:chemistry* / Q000378:metabolism; D012972:Sodium Hydroxide / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013818:Thermogravimetry; D014465:Ultrasonics
D000447:Aldehydes; D002241:Carbohydrates; D011134:Polysaccharides; D012972:Sodium Hydroxide; C007916:hemicellulose; D008031:Lignin