高底物浓度木质纤维素快速酶解发酵（RaBIT）技术的基础研究

Biorefinery of lignocellulosic biomass for fuel ethanol production is of great importance for energy security, environmental protection and social sustainability. However, high enzyme loading and low productivity lead to high cost of lignocellulosic ethanol production, which becomes the key barrier for large-scale commercialization. To address the two key issues of high enzyme loading and low productivity, a rapid enzymatic hydrolysis and fermentation technology (RaBIT: Rapid Bioconversion with Integrated recycle Technology) was invented based on novel process design. This project will study the adsorption properties of purified key cellulases on different cellulose allomorphs and pretreated lignin, establish adsorption models, based on gained adsorption knowledge design the step of enzyme recycling via unhydrolyzed lignocellulosic biomass in RaBIT process to increase enzyme recovery, optimize the supplementary enzyme cocktail, and realize a significant reduction of enzyme loading. This project will also study the mechanisms of oligomeric sugar accumulation during rapid hydrolysis (23 h) at a high solids loading and efficient oligomeric sugar degradation during rapid fermentation (23 h), coordinate rapid hydrolysis and rapid fermentation through oligomeric sugar, realize efficient integration of hydrolysis and fermentation in RaBIT process and substantial enhancement of ethanol productivity. This project will advance lignocellulosic biorefinery technologies and meanwhile lay the foundation for understanding the mechanism of lignocellulosic biomass enzymatic hydrolysis at a high solids loading.

木质纤维素生物炼制生产燃料乙醇在保障能源安全、保护环境和促进社会的可持续发展等方面具有非常重要的意义。然而，炼制过程中的高酶用量和低生产强度造成了生产成本过高、限制了纤维素乙醇的大规模工业化。本项目针对这两个关键问题，基于整体工艺的创新设计，前期发明了快速酶解发酵（RaBIT）技术；通过模型研究纯化的各种核心纤维素酶在不同类型纤维素和预处理后木质素上的吸附特性，设计提升RaBIT工艺利用酶解后残留的木质纤维素吸附回收酶、优化补加酶配方，实现酶用量的大幅度减少；研究高底物浓度工艺快速酶解（23 h）寡糖积累以及之后快速发酵（23 h）寡糖高效降解的机理，通过寡糖协调快速酶解发酵的关系，实现RaBIT工艺中酶解与发酵的高效整合，大幅度提升生产强度。本项目的研究将推进木质纤维素生物炼制技术的发展，同时对揭示木质纤维素高底物浓度酶解机理具有重要意义。

本项目以木质纤维素生物炼制生产燃料乙醇为研究对象，针对其中酶用量大和生产强度低的问题，基于整体工艺的创新设计，从快速酶解发酵和酶吸附回收利用的角度开展研究。通过实验研究结合模型解析了混合纤维素酶和核心纤维素酶在不同类型纤维素和不同预处理后木质素上的吸附特性；研究了高底物浓度酶解过程中糖释放规律以及糖在发酵过程中的转化特性；进一步开发了基于酶解特性和酶在未水解木质纤维素上吸附特性的快速酶解酶回收工艺、基于发酵特性的快速葡萄糖和木糖共发酵及细胞回收工艺，实现了酶用量降低30%-50%、乙醇生产强度提升2-3倍。