title: Revealing the structure and distribution changes of Eucalyptus lignin during the hydrothermal and alkaline pretreatments.
abstract: An integrated pretreatment process based on hydrothermal pretreatment (HTP) followed by alkaline pretreatment has been applied to treat Eucalyptus. The chemical composition and structure changes of lignin during the pretreatment were comprehensively characterized. The surface morphology of the cell walls and lignin distribution of the pretreated Eucalyptus were detected by scanning electron and confocal Raman microscopies. It was found that the chemical bonds between lignin and hemicelluloses were cleaved during the pretreatment. The results also indicated that the contents of β-O-4', β-β', and β-5' linkages were decreased with the increase of hydrothermal pretreatment temperature and the cleavage of β-O-4' linkages in lignin was accompanied with repolymerization reactions.31P NMR analysis showed that the content of aliphatic OH was reduced as the temperature increased and the total phenolic OH was elevated and then declined with the increase of temperature. Raman spectra analysis revealed that the dissolution rate of lignin in the secondary wall regions was faster than that in cell corner middle lamella regions during the pretreatment. These results will enhance the understanding of the cell wall deconstruction during the pretreatment and the mechanism of the integrated pretreatment process acting on Eucalyptus.
authors.affiliation: Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing, 100083, China.
authors.forename: Chenzhou
authors.initials: C
authors.lastname: Wang
authors.affiliation: Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing, 100083, China.
authors.forename: Hanyin
authors.initials: H
authors.lastname: Li
authors.affiliation: Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing, 100083, China.
authors.forename: Mingfei
authors.initials: M
authors.lastname: Li
authors.affiliation: Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing, 100083, China. bianjing31@bjfu.edu.cn.
authors.forename: Jing
authors.initials: J
authors.lastname: Bian
authors.affiliation: Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing, 100083, China. rcsun3@bjfu.edu.cn.|State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, 510640, China. rcsun3@bjfu.edu.cn.
authors.forename: Runcang
authors.initials: R
authors.lastname: Sun
mesh_terms: D000468:Alkalies / Q000737:chemistry*; D002241:Carbohydrates / Q000737:chemistry; D005052:Eucalyptus / Q000737:chemistry*; D008031:Lignin / Q000737:chemistry* / Q000648:ultrastructure; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D008970:Molecular Weight; D000073758:Nonlinear Optical Microscopy; D000073893:Sugars / Q000737:chemistry; D013696:Temperature
chemical_list: D000468:Alkalies; D002241:Carbohydrates; D000073893:Sugars; D008031:Lignin