The efficient utilization of lignocellulosic biomass for biofuel production has received increasing attention. Previous studies have investigated the pretreatment process of biomass, but the detailed enzymatic hydrolysis process of pretreated biomass remains largely unclear. Thus, this study investigated the pretreatment efficiency of dilute alkali, acid, hydrogen peroxide and its ultimate effects on enzymatic hydrolysis. Furthermore, to better understand the enzymatic digestion process of alkali-pretreated sweet sorghum straw (SSS), multimodal microscopy techniques were used to visualize the enzymatic hydrolysis process. After pretreatment with alkali, an enzymatic hydrolysis efficiency of 86.44% was obtained, which increased by 99.54% compared to the untreated straw (43.23%). The FTIR, XRD and SEM characterization revealed a sequence of microstructural changes occurring in plant cell walls after pretreatment, including the destruction of lignin–polysaccharide interactions, the increase of porosity and crystallinity, and reduction of recalcitrance. During the course of hydrolysis, the cellulase dissolved the cell walls in the same manner and the digestion firstly occurred from the middle of cell walls and then toward the cell wall corners. The CLSM coupled with fluorescent labeling demonstrated that the sclerenchyma cells and vascular bundles in natural SSS were highly lignified, which caused the nonproductive bindings of cellulase on lignin. However, the efficient delignification significantly increased the accessibility and digestibility of cellulase to biomass, thereby improving the saccharification efficiency. This work will be helpful in investigating the biomass pretreatment and its structural characterization. In addition, the visualization results of the enzymatic hydrolysis process of pretreated lignocellulose could be used for guidance to explore the lignocellulosic biomass processing and large-scale biofuel production.

中文翻译：

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甜高粱秸秆的预处理及其酶解：深入了解水解过程的结构变化和可视化

木质纤维素生物质在生物燃料生产中的有效利用受到越来越多的关注。以前的研究已经研究了生物质的预处理过程，但预处理生物质的详细酶水解过程仍不清楚。因此，本研究调查了稀碱、酸、过氧化氢的预处理效率及其对酶水解的最终影响。此外，为了更好地了解碱预处理的甜高粱秸秆（SSS）的酶消化过程，使用多模态显微镜技术对酶水解过程进行可视化。经碱预处理后，酶解效率为86.44%，与未经处理的秸秆（43.23%）相比提高了99.54%。FTIR，XRD 和 SEM 表征揭示了预处理后植物细胞壁发生的一系列微观结构变化，包括木质素-多糖相互作用的破坏、孔隙率和结晶度的增加以及顽固性的降低。在水解过程中，纤维素酶以同样的方式溶解细胞壁，首先从细胞壁中部开始消化，然后向细胞壁角部进行消化。CLSM 结合荧光标记表明，天然 SSS 中的巩膜细胞和维管束高度木质化，导致纤维素酶与木质素的非生产性结合。然而，有效的脱木质素显着提高了纤维素酶对生物质的可及性和消化率，从而提高了糖化效率。这项工作将有助于研究生物质预处理及其结构表征。此外，预处理木质纤维素酶解过程的可视化结果可用于指导探索木质纤维素生物质加工和大规模生物燃料生产。