In addition to cellulose and lignin, hemicellulose is an important biomass material. Recently, hemicellulose and its derivatives and materials have attracted increasing attention owing to their unique structures, improved properties, and promising application potential, and many reports on the extraction, isolation, and modification of hemicellulose are currently available. We summarized the recent developments of hemicellulose and its derivatives and materials by focusing on the extraction, purification, and modification of hemicellulose. The synthesis of hemicellulose-based derivatives and materials was also reviewed. Various methods of extracting, isolating, and modifying hemicellulose were discussed. Remaining challenges related to hemicellulose extraction, purification, and application were mentioned, and directions for further research on hemicellulose were proposed.

Nanocellulose composites combine the advantages of nanocellulose and composites. Recently, nanocellulose composites have been received more attentions due to their improved properties and promising broad applications. In the past, rapid progress has been made in the synthesis, properties, and mechanism of nanocellulose composites and potential applications were reported. There are a few reports on the increasing applications of nanocellulose composites with focus on the biomedical field, environmental field, electrode and sensor applications. In this article, the recent development of nanocellulose composites was reviewed via some typical examples. In addition to the synthesis methods, improved properties and potential applications were discussed. The problems and future applications of nanocellulose composites were also suggested.

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.

The purpose of this study was to explore the differences of the hemicelluloses extracted by hydrothermal pretreatment using water and alkaline solutions(Na OH or KOH). The physicochemical properties and structural characteristics of two water-soluble and four alkali-soluble hemicelluloses extracted from the triploid of Populus tomentosa Carr. through the hydrothermal pretreatment were comparatively studied. It was observed that the alkalis(Na OH and KOH) were more effective than distilled water as extractants. Sugar analysis showed that xylose(66.83%~86.49%) was the major constituent, followed by glucose(6.83%~18.49%). Mannose(1.40%~8.42%), galactose(2.17%~4.05%), and arabinose(0.21%~2.26%) were also detected in the hemicellulosic fractions. The results of gelpermeation chromatography(GPC) indicated that the hemicelluloses extracted using the alkaline solutions had relatively higher molecular weights than those solubilized in distilled water. Further, based on spectroscopic ¹Hnuclear magnetic resonance(¹H-NMR) and two-dimensional heteronuclear singular quantum correlation(2D-HSQC) analyses, it was confirmed that the hemicellulosic fractions had a major structure of(1→4)-β-D-xylan and a minor structure of(1→4)-α-D-glucan with small amounts of substituted sugars and glucuronic acid attached.