title: Structural elucidation of Eucalyptus lignin and its dynamic changes in the cell walls during an integrated process of ionic liquids and successive alkali treatments.
abstract: An integrated process based on ionic liquids ([Bmim]Cl and [Bmim]OAc) pretreatment and successive alkali post-treatments (0.5, 2.0, and 4.0% NaOH at 90°C for 2h) was performed to isolate lignins from Eucalyptus. The structural features and spatial distribution of lignin in the Eucalyptus cell wall were investigated thoroughly. Results revealed that the ionic liquids pretreatment promoted the isolation of alkaline lignin from the pretreated samples without obvious structural changes. Additionally, the integrated process resulted in syringyl-rich lignin macromolecules with more β-O-4' linkages and less phenolic hydroxyl groups. Confocal Raman microscopy analysis showed that the dissolution behavior of lignin was varied in the morphologically distinct regions during the successive alkali treatments, and lignin dissolved was mainly stemmed from the secondary wall regions. These results provided some useful information for understanding the mechanisms of delignification during the integrated process and enhancing the potential utilizations of lignin in future biorefineries.
authors.affiliation: Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing 100083, China.
authors.forename: Han-Yin
authors.initials: HY
authors.lastname: Li
authors.affiliation: Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing 100083, China.
authors.forename: Chen-Zhou
authors.initials: CZ
authors.lastname: Wang
authors.affiliation: Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing 100083, China.
authors.forename: Xue
authors.initials: X
authors.lastname: Chen
authors.affiliation: Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing 100083, China; State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou 510640, China.
authors.forename: Xue-Fei
authors.initials: XF
authors.lastname: Cao
authors.affiliation: Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing 100083, China. Electronic address: sunshaoni@126.com.
authors.forename: Shao-Ni
authors.initials: SN
authors.lastname: Sun
authors.affiliation: Beijing Key Laboratory of Lignocellulosic Chemistry, Beijing Forestry University, Beijing 100083, China.
authors.forename: Run-Cang
authors.initials: RC
authors.lastname: Sun
mesh_terms: D000468:Alkalies / Q000032:analysis; D002473:Cell Wall / Q000737:chemistry*; D005052:Eucalyptus / Q000737:chemistry*; D052578:Ionic Liquids / Q000737:chemistry; D008031:Lignin / Q000302:isolation & purification*; D018547:Plant Stems / Q000737:chemistry
chemical_list: D000468:Alkalies; D052578:Ionic Liquids; D008031:Lignin
keywords: Confocal Raman microscopy; Eucalyptus; Ionic liquids pretreatment; Lignin; Successive alkali treatments