Design and Assembly of a Multi-enzyme CO2 Fixation System

化石燃料的使用不仅导致了资源和能源的短缺，而且还带来了烟雾和温室气体等环境问题。利用太阳能、生物质等可再生资源生产能源和化学品已成为可持续发展的重要方向。以二氧化碳为基础的第三代生物技术是目前生物技术研究的热点之一。在后一方面，酶法二氧化碳转化的优点是没有副产物，工艺简单，易于调整。然而，目前二氧化碳转化的主要问题是缺乏有效的还原系统和低效的辅助因子再生系统来消除叶栅的瓶颈。FixZyme项目旨在构建一种简单但有效的固定二氧化碳的酶级联，它采用四步法逐步还原二氧化碳以生成二羟基丙酮，这是一种有前景的工业前体。对于高效的辅因子再生，将评估酶(一种耐氧性[NiFe]-氢酶，使用H2来还原NAD)和光催化/电化学方法。创新的酶融合和共固定化方法将被用来构建多酶级联。通过使用蛋白质工程，单个氧化还原酶将被量身定做，以优化催化效率和稳定性。在全面的计算机辅助建模和模拟的指导下，将获得对结构-功能关系、代谢物通量和形态的基本理解，这将进一步为迭代过程和蛋白质工程试验奠定基础。为了实现高效、高效的二氧化碳固定系统的目标，德国和中国的合作伙伴将联合他们在蛋白质工程、酶生产和纯化、基因工程、计算生物学、固定化和物理化学分析方面的专业知识。FixZyme项目不仅对于高效生物催化剂的合理设计具有重要意义，而且对于理解支配自组装的表面相互作用及其潜在的进化原理也具有重要意义。

The use of fossil fuels not only leads to a shortage of resources and energy but also to environmental problems such as smog and greenhouse gases. The use of renewable resources such as solar energy and biomass to produce energy and chemicals has become an important direction for sustainable development. The third generation of biotechnology based on CO2 is one of the hot spots in biotechnology research at present. In the latter respect, the advantage of enzymatic CO2 conversion is that there are no byproducts and the processes are simple and easily tunable. At present, however, the main problems of CO2 conversion are the lack of efficient reduction systems and inefficient cofactor regeneration systems to debottleneck the cascades. The FixZyme project aims to construct a simple, yet effective enzyme cascade for CO2 fixation, which employs a four-step process to stepwise reduce CO2 to yield dihydroxyacetone, a promising industrial precursor. For efficient cofactor regeneration, both enzymatic (an oxygen-tolerant [NiFe]-hydrogenase using H2 to reduce NAD) and photocatalytic/electrochemical approaches will be evaluated. Innovative enzyme fusion and co-immobilization methods will be employed to construct the multi-enzyme cascade. Individual oxidoreductases will be tailored towards optimized catalytic efficiencies and stabilities by using protein engineering. Guided by comprehensive computationally assisted model building and simulations, a fundamental understanding of structure-function relationships, metabolite fluxes, and morphologies will be gained, which further builds the foundation of iterative process and protein engineering trials. To achieve the goal of a highly active and efficient CO2-fixation system, the German and Chinese partners will join their expertises in protein engineering, enzyme production and purification, genetic engineering, computational biology, immobilization and physicochemical analysis. The FixZyme project is of great significance not only for the rational design of highly efficient biocatalysts but also for understanding surface interactions that govern self-assembly and their underlying evolutionary principles.