预处理生物质木质素对纤维素酶的吸附抑制机制及酶修饰机理研究

A great hindrance in commercial production of cellulosic ethanol is the unproductive adsorption of lignin. It can be effectively improved by the combination of pretreatment and cellulase modification. However the inhibition mechanism of cellulase adsorption by lignin and the internal relation between cellulase modification and its hydrolysis properties are not unclear. In this project, the residual lignins are separated from pretreated forestry and agricultural residues and their characters such as molecular weight, functional group, wettability, charge density and so on are detected. And then the relationships between the characters of residual lignins and cellulase adsorption ability, constituents of cellulase, conformation change of protein and enzyme activity are deep studied to reveal the inhibition mechanism of lignin and make clear the effect of lignin adsorption on the composition of cellulase. In addition, the hydrophilic and electronegative polymer of HO-PEG (polyethylene glycol)-COOH is chosen to modify the enzymes which can be easy adsorbed by residual lignin. Based on the inner connection between characters of modified cellulase and unproductive adsorption of residual lignin, enzymatic hydrolysis and phase separation characterization, the best modified cellulase is screened out, which can effectively decrease the unproductive adsorption of residual lignin, efficiently hydrolyze the cellulose of biomass and be recycled by attemperation. This study provides a practical significance for reducing the cost of cellulosic ethanol production.

木质素对纤维素酶的无效吸附是纤维乙醇工业化生产的重要阻碍，从生物质原料预处理和酶修饰两方面同时入手是有效改善手段。然而，木质素对纤维素酶系组分的吸附抑制机制以及修饰酶结构特点与其水解特性之间的内在联系尚不明确。本项目通过系统研究预处理残留木质素分子量、结构基团、亲水/疏水性、表面负电性等物理化学特性与纤维素酶吸附能力、组成成分、构象变化、水解活力等特性之间的关系，阐明木质素对纤维素酶的吸附抑制机制，明确无效吸附对纤维素酶系组分的影响；采用亲水、负电以及温敏特性的羟基-聚乙二醇-羧基聚合物着重对易与木质素结合的纤维素酶组分进行修饰，基于修饰酶结构特征与无效吸附、水解转化、相分离特性之间的内在联系，制备出稳定、高效、可温控自分离的新型修饰纤维素酶。研究成果将有效降低木质素对纤维素酶的无效吸附，高效转化木质纤维原料中的纤维素，实现酶的回收利用，对降低纤维乙醇工业化生产成本有重要的现实意义。