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.
Sci Rep. 2017 Apr 4;7(1):593. doi: 10.1038/s41598-017-00711-w.
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. P 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.
已应用基于水热预处理 (HTP) 后接碱性预处理的综合预处理工艺来处理桉树。综合表征了预处理过程中木质素的化学组成和结构变化。通过扫描电子显微镜和共焦拉曼显微镜检测了预处理桉树细胞壁的表面形态和木质素分布。结果表明，预处理过程中木质素与半纤维素之间的化学键被切断。结果还表明，随着水热预处理温度的升高和木质素中β-O-4'键的断裂，β-O-4'、β-β'和β-5'键的含量降低，β-O-4'键的断裂伴随着重排反应。31P NMR 分析表明，随着温度的升高，脂肪族 OH 的含量减少，而总酚 OH 则升高，然后随着温度的升高而下降。拉曼光谱分析表明，在预处理过程中，木质素在次生壁区域的溶解速率快于在细胞角中层区域的溶解速率。这些结果将增强对预处理过程中细胞壁解构以及综合预处理工艺对桉树作用机制的理解。
