二氧化碳酶法捕集系统中的介尺度结构和调控机制研究

Carbon dioxide (CO2) emmission generated during fossil fuel combustion, a major contributor to climate change, has become the most challenging environmental issue in the world. Technology of CO2 capture and storage provides a solution to reduce CO2 emmission and mitigate climate change. Due to high cost, high energy consumption and secondary pollution during capture CO2 using adsorption, absorption and membrane, CO2 capture using enzyme which is environmentally friendly and specific has attracted more and more attention. However, its industrial application has been limited by its instability. In this project, to improve the stability of carbonic anhydras (CA), effects of residue mutations and environmental factors on conformation and biofunctions will be investigated using molecular simulations based on the meso-scale. Gene engineering and protein engineering are applied to produce evolved CA whose activity and stability will be examined. A model describing the interactions between CA and carrier surface in the immobilized CA system will be established to elucidate how carrier material and environmetal factors affect the interactions and biostability during immobilization. Regulation mechanism of immobilization will be disclosed based on the meso-scale. A novel immobilized CA system will be developed to capture CO2 with high efficiency. This study will provide a guideline for preparation of stable and reuseable CO2 capture system using immobilized CA.

传统化石能源利用中释放大量CO2，由此导致的温室效应已成全球最大环境问题。目前CO2捕集多采用吸收、吸附和膜法等，存在成本高、再生能耗大及二次污染问题。利用碳酸酐酶(CA)捕集CO2具备高效专一、环境友好等特点而广受关注。但CA稳定性差、易失活，严重限制其工业应用。本项目以碳酸酐酶CO2捕集系统为研究对象，从介尺度结构出发，利用分子模拟考察残基突变和环境因素对酶生物构象和性质的影响，以获得热稳定性酶；通过动力学模拟对突变位点优化，实现酶生物特性的调控改造；采用基因工程和蛋白质工程方法制备改性酶并验证其酶活和生物稳定性；建立酶固定化过程中酶与载体的表界面相互作用模型，探讨载体材料性质和pH等外界因素对酶与载体相互作用和酶生物特性的影响，从介尺度水平揭示酶固定化过程的调控机制；建立新型CO2碳酸酐酶捕集系统，为制备稳定且可多次重复利用的CO2酶捕集系统, 实现对CO2的高效捕集奠定理论基础。

本项目通过对人和细菌碳酸酐酶的结构及功能的分析比较，选择以人碳酸酐酶为改造对象。从介尺度结构出发，利用分子模拟手段考察氨基酸序列和环境因素对酶的二级结构、生物构象和性质的影响，确定了L204K的改造对其介尺度水平的影响，及介尺度水平变化对二级和三级结构的影响；在成功构建工程菌的基础上，实现改造的碳酸酐酶在大肠杆菌内的表达；通过固定化载体的不同制备方法确定不同方法对载体比表面积和孔径大小的影响，并将载体进行半胱氨酸改性，实现其与改造的碳酸酐酶的定向联接,实现交联后的质量控制。最后考察了以改造碳酸酐酶为基础的新型二氧化碳捕集体系中其捕集能力。这一新型体系在碱性条件下稳定，对温度的稳定性较未改造的碳酸酐酶体系提升了近20oC, 固定化对其提升更为显著。与传统体系相比，且这一体系对阴离子的耐受性也显著提升。这种新型生物催化剂的稳健性和高效性使其成为CO2捕获的有竞争力的候选者。