双相体系预处理过程中细胞壁半纤维素的解离迁出机制及其对酶解效率的影响

Pretreatment, which can disrupt biomass recalcitrance in varying degrees, is conducive to the conversion of biomass components into fuels or chemicals. The pretreatment of lignocellulosic biomass with biphasic system exhibits several advantages, such as relatively mild reaction conditions, high efficiency and less by-products, which has a broad application prospect in the efficient utilization of biomass components. However, the dissociation and migration mechanism of cell wall hemicelluloses during the biphasic system pretreatment and its influence on enzymatic hydrolysis are still unclear. In this project, corn straw will be selected as a raw material. The degradation behavior, microstructure and spatial distribution changes of the cell wall components during the biphasic system pretreatment will be comprehensively investigated by chromatography, NMR, microscopic and microspectroscopic techniques. The dissociation and migration mechanism of the cell wall hemicelluloses during the biphasic system pretreatment will be interpreted at the ultra-structural level. The influence of the cell wall microstructure, chemical and topochemical changes on the production of furfural and enzymatic hydrolysis efficiency of cellulose will be determined. Furthermore, the mechanism of the efficient transformation of hemicelluloses into furfural and its promotion effects on the enzymatic hydrolysis of cellulose via the biphasic system pretreatment will be discussed. The aim of this project is to realize the efficient conversion of cell wall hemicelluloses into furfural and at the same time to improve the enzymatic hydrolysis efficiency of cellulose. These approaches may provide new ideas for the efficient utilization of lignocellulosic biomass.

预处理可在不同程度上破除植物细胞壁的抗降解屏障，有利于生物质组分转化为能源或化学品。双相体系预处理具有条件温和、效率高、产物相对单一等优点，在生物质组分的高效转化利用方面具有广阔的应用前景。然而，双相体系预处理过程中细胞壁半纤维素在超微结构水平上的解离迁出机制及其对酶解效率的影响尚不清楚。本项目玉米秸秆为研究对象，采用色谱、核磁、显微及显微光谱等多尺度表征手段，深入研究双相体系预处理过程中细胞壁组分的降解、微观结构及微区分布变化规律，从超微结构水平揭示双相体系预处理过程中细胞壁半纤维素的解离迁出机制，明确木质纤维细胞壁微观结构、化学和区域化学变化对糠醛产率及纤维素酶解效率的影响，探讨双相体系预处理高效转化细胞壁半纤维素为糠醛的机理，并阐明其破除细胞壁抗降解屏障，促进纤维素酶解效率的作用机制，实现细胞壁半纤维素高效转化为糠醛的同时，提高纤维素的酶解效率，为木质纤维资源的高效利用提供新思路。

木质纤维生物质的预处理技术是破坏生物质细胞壁抗降解屏障使其高效地转化为能源及化学品的关键技术。本项目采用双相体系对玉米秸秆原料进行预处理，采用色谱、核磁、显微及显微光谱等多尺度表征手段，深入探究了双相体系预处理过程中细胞壁组分的降解、微观结构及微区分布的变化规律。研究结果表明，双相体系2-甲基四氢呋喃/水和甲基异丁基甲酮/水可将玉米秸秆中的半纤维素组分高效转化为糠醛，且后续纤维素残渣的酶解效率显著提高；探索了有机溶剂和水的体积比、催化剂种类和用量、反应温度和时间对糠醛产率和纤维素酶解效率的影响，阐明了双相体系预处理过程中半纤维素的降解机理及促进纤维素酶解效率的作用机制。研究发现双相体系预处理可有效脱除生物质中的半纤维素和酚类物质，破坏植物细胞壁的形态学结构和组分的微区分布，提高纤维素的酶解效率。利用荧光显微镜和共聚焦拉曼显微技术确定了双相体系预处理对玉米秸秆细胞壁的形貌变化及主要组分局部化学变化的影响，发现预处理后细胞壁发生明显剥离，木质素和羟基肉桂酸在薄壁细胞和厚壁细胞各层的浓度显著下降，而碳水化合物浓度变化不大，使得包覆在细胞壁内的纤维素充分暴露，从而增加了纤维素酶对纤维素的可及度。综上所述，双相体系预处理促进酶解效率是多种变化协同作用的结果。此外，探索了速生桉木在双相体系和γ-戊内酯/水预处理过程中的组分结构变化及酶解行为，为木质纤维资源的高效利用提供新思路。