Comparative study of alkali- and acidic organic solvent-soluble hemicellulosic polysaccharides from sugarcane bagasse.
Two-stage treatments of sugarcane bagasse with mild alkali and acidic 1,4-dioxane were performed. Pretreatment with 1M NaOH aqueous solution at 20, 25, 30, 35, and 40 degrees C for 18 h released 55.5%, 57.3%, 59.1%, 60.9%, and 62.1% of the original hemicelluloses, respectively. Post-treatment of the corresponding alkali-treated residue with 1,4-dioxane-2M HCl (9:1, v/v) at 87 degrees C for 2h, respectively, degraded 11.6%, 11.9%, 11.4%, 10.9%, and 10.6% of hemicelluloses (% dry starting material). It was found that the five alkali-soluble hemicellulosic preparations contained a much higher amounts of xylose (78.0-82.2%) and slightly higher uronic acids (4.8-5.8%), mainly 4-O-methyl-alpha-d-glucopyranosyluronic acid, but were lower in arabinose (9.3-11.7%) and glucose (2.2-4.1%) than those of the corresponding five acidic dioxane-degraded hemicellulosic fractions in which xylose (44.9-46.8%), arabinose (35.9-38.1%), and glucose (13.0-13.7%) were the major sugar constituents. The studies revealed that the five alkali-soluble hemicellulosic preparations were more linear and acidic, and had a large molecular weight (35,200-37,430 g mol(-1)) than those of the hemicellulosic fractions (12,080-13,320 g mol(-1)) degraded during the acidic dioxane post-treatment. This demonstrated that the post-treatment with acidic dioxane under the condition used resulted in substantial degradation of the hemicellulosic polymers. The 10 hemicellulosic samples were further characterized by FT-IR and 1H and 13C NMR spectroscopy, GPC and thermal analysis, and the results are reported.
Xu
F
F
College of Forestry, North-Western Science and Technology University of Agriculture and Forestry, Yangling 712100, China.
Sun
J X
JX
Liu
C F
CF
Sun
R C
RC
D002482:Cellulose / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008031:Lignin / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008970:Molecular Weight; D011134:Polysaccharides / Q000737:chemistry* / Q000302:isolation & purification; D031786:Saccharum; D012972:Sodium Hydroxide; D012995:Solubility; D012997:Solvents; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature
D011134:Polysaccharides; D012997:Solvents; D012972:Sodium Hydroxide; D002482:Cellulose; D008031:Lignin; C027433:bagasse