Efficient extraction and characterization of polymeric hemicelluloses from hybrid poplar

Hemicelluloses were isolated from hybrid poplar with the single-step alkaline extraction. Neutralization and subsequent ethanol precipitation were used to recover them. Their structures were investigated using sugar analysis, Fourier transform infrared and (13)C nuclear magnetic resonance spectroscopy. The hemicelluloses were characterized by particle size analyzer, gel permeation chromatography and thermogravimetric analyzer. 36.4% and 50.4% of the original hemicelluloses were isolated in the form of polymer by neutralization and precipitation, respectively. The hemicellulosic fraction (HA) by neutralization was more homogeneous in sugar components than the one (HB) by precipitation. However, hemicellulose isolated by both of the process has chemical structure, as were (4-O-methylglucurono)-d-xylans. The weight average molecular mass of HA was 17,480 g mol(-1), higher than one of HB (14,670 g mol(-1)) and they were both with a low polydispersity. HA had lower zeta potential and higher thermal stability than HB. Therefore, the procedures in this study were efficient for the isolation and the recovery of polymeric hemicelluloses with different properties.