木质纤维素材料预处理过程中木质素结构和性质的变化及其对纤维素酶吸附的影响及机制

将资源丰富且可再生的木质纤维素通过生物转化生产液体燃料和大宗化学品，是当前研究的热点。生物质生物转化的关键步骤是首先将碳水化合物利用酶水解生成单糖。但木质素的存在抑制了纤维素的酶水解，因为它既作为物理屏障限制酶接近纤维素，又能吸附纤维素酶导致非反应性的结合。预处理是改善纤维素酶解性的最要一步，预处理过程中木质素的含量、结构和性质等将发生变化。但至今为止，木质素对纤维素酶复杂组分中不同蛋白的吸附特征尚不清楚，木质素结构和性质与纤维素酶吸附之间的相互关系以及预处理对木质素吸附纤维素酶的影响和机制尚未阐明。针对上述问题，本项目将系统地开展预处理对木材和非木材原料中木质素结构和性质等的影响、木质素对纤维素酶不同蛋白的吸附特征、预处理对木质素吸附蛋白的影响规律及机制等研究。这对完善木质纤维素酶解机制、设法减轻预处理后木质素对酶解的不利影响、有针对性地复配纤维素酶系或进行菌株改造等具有重要参考价值。

Due to the limited availability of fossil carbon,as well as environmental concerns, comprehensive utilization of lignocellulosics for fuel and chemical production has currently raised much interest. A key step for bioconversion of lignocellulosic materials to fuels and chemcials is that the cellulose and hemicelluloses are first hydrolyzed by enzymes to fermentable sugars. But the recalcitrant structure of lignocellulose, which is caused by avariety of factors such as the inaccessibility of the cellulose, due to its close association with the hemicelluloses and lignin, crystallinity, etc., makes it dif?cult to hydrolyze enzymatically.Therefore,lignocellulosic materials must ?rst be pretreated to improve enzymatic hydrolysis.In the proposed pretreatment methods, pretreatment with dilute sulfuric acid is common method. The hemicellulose was dissolved out during the acid pretreatment,and accessibility of cellulose was improved. However, the residual lignin remaining in the pretreated cellulosic substrates signi?cantly in?uences subsequent enzymatic hydrolysis as lignin acts as both a physical barrier,.restricting access of cellulases to cellulose, and as an attractant to cellulases,.resulting in non-productive binding. The physical/chemical characteristics of lignin were also changed by dilute acid pretreatment. It has been shown that the chemical and physical structure of lignin plays a significant role in determining the magnitude of inhibition it contributes to hydrolysis. But to date, less research has been conducted on the adsorption features of different protein in cellulase enzyme systems to ligin, the relationship between the structures and properties of lignin and adsorption of cellulase to lignin, and effect of pretreatment process on adsorption of cellulase to lignin.In the project, the residual lignin were isolated from dilute acid pretreated wood and nonwood biomass materials, and structurally characterized. The changes of lignin contents and properties of lignin in the cellulosic substrates before and after pretreatment, the adsorption rules of different protein in cellulase enzyme systems to lignin, and the effect of dilute acid preteatment on adsorption of cellulases to lignin and its mechanism,etc., were studied.It was valuable for finding suibable methods to decrease lignin inhibitory effect, improving enzymatic-hydrolysis of lignocellulose by adding essential enzyme components and reconstruction of the composition of the enzyme systems.