Characterization of Hemicelluloses Extracted from Populus tomentosa Carr. by the Hydrothermal Method with Ethanol

The aim of this study was to investigate the hemicelluloses extracted from Populus tomentosa Carr. by the hydrothermal method with ethanol. The influence of ethanol concentration on the hemicellulosic fractions was systematically studied. The chemical compositions and structural features of the hemicellulosic fractions were investigated by a combination of sugar analysis, gel-permeation chromatography, Fourier transform infrared spectroscopy, and one-dimensional proton and carbon-13 nuclear magnetic resonance, and two-dimensional heteronuclear single quantum coherence spectroscopy. Neutral sugar analysis of the hemicellulosic fractions revealed that a higher ethanol concentration (45%~80%) favored the isolation of hemicelluloses with more side chains and lower glucose contents. The molecular weights of these polysaccharides ranged between 2842 g/mol and 5101 g/mol. The results of this study indicate that the hydrothermal ethanol process provides a new pretreatment strategy for the isolation and extraction of biomass.