Abstract: Native lignocellulosic biomass has limited accessibility to enzymes and microorganisms due to its complex cell wall structure of cellulose-hemicellulose-lignin. Therefore, pretreatment is a prerequisite to overcome recalcitrance of biomass and enhance bio-chemical conversion ratio of polysaccharides. Compared with other methods, high temperature liquid hot water pretreatment has the advantages of no chemical addition and less inhibitory products. In the present study, different structural changes at plant tissue, cellular, and cell wall levels were investigated to understand the decomposition mechanism of sugarcane bagasse cell wall in the liquid hot water pretreatment. Transmission electron microscopy (TEM) images showed that sugarcane bagasse cell walls were composed of middle lamella (ML) layers, primary wall (P) layers, and secondary wall layers (S). While after the pretreatment, the boundaries among the ML, P and S layers of treated samples could not be distinguished exactly. The data from scanning electron microscopy and energy dispersive X-ray analysis(SEM-EDXA)showed that migration of lignin happened among different cell wall layers. Moreover, pseudo-lignin, the degradation products of lignin and xylan, appeared on the surface of pretreated sugarcane bagasse. Furthermore, Raman spectra of treated sugarcane bagasse indicated that distribution of cellulose in the cell wall was homogenized, and the difference in chemical composition was reduced.

Key words: liquid hot water, biomass, microstructure, chemical analysis

摘要： 木质纤维素类物质中天然纤维素与半纤维素、木质素等组分交联形成了坚固的细胞壁,对纤维素酶水解和微生物消化表现出一定的抗性,原料预处理可以克服细胞壁抗性,提高木质纤维多糖生化转化效率.从细胞壁超微结构层次入手,对甘蔗渣细胞壁在高温液态水预处理过程中的解构机理进行了深入研究.未处理甘蔗渣细胞壁分层现象明显,由外至内分别为胞间层(ML)、初生壁(P)及次生壁(S),高温液态水预处理后各层界线变得模糊.SEM-EDXA分析表明细胞壁各层木质素分布发生了迁移,水解液中的木聚糖和木质素衍生物在细胞壁表面凝集生成类木质素滴状沉淀物.拉曼光谱分析结果显示预处理后纤维素在细胞壁各层分布趋于均质化.

关键词: 高温液态水, 生物质, 显微结构, 化学分析