Impact of anti-solvents on the characteristics of hemicellulose fractionated from bleached bamboo pulp using lithium bromide hydrates.

Selective fractionation/dissolution of hemicellulose with no or less degradation from biomass resources is a prerequisite for its high-value material utilization. Yet, the impact of anti-solvents on the properties of regenerated/precipitated hemicellulose after dissolution is still unclear. Herein, lithium bromide (LiBr) hydrate as a green solvent was used for fractionating hemicellulose from bleached bamboo pulp (BBP). Subsequently, the effect of anti-solvents (i.e., water, ethanol and acetone) on the characteristics of regenerated hemicellulose was comprehensively investigated. Results showed that the maximum removal rate of hemicellulose was 84.4 %, and the corresponding yield of pure hemicellulose precipitated by acetone was up to 84.0 %, which was influenced by the polarity of anti-solvent. Structural characterizations revealed that resultant hemicelluloses with degree of polymerization of 184-290 were arabinoxylan, and the molecular structure of the regenerated hemicellulose did not change significantly after fractionation and regeneration. However, importantly, it was found that the hemicellulose regenerated with different anti-solvents exhibited distinct multiscale morphology and nanostructures, which was attributed to the different reconstruction of hydrogen bonding and different extent of recrystallization among hemicellulose chains during regeneration with distinct anti-solvents. The obtained results could provide a theoretical basis for further modification, processing, and more advanced applications of hemicellulose.