EFRI-PSBR: Continuous Liquid Fuel Production via Scalable Biosynthesis of Enzyme-Quantum Dot Hybrid Photocatalysts

摘要知识价值：本次招标的重点是开发光合生物精炼厂的概念，其中微生物被用于阳光和二氧化碳（CO2）的转化，以生产生物燃料和生物产品物种。需要一种系统方法，并且系统应该是可伸缩的。生命周期分析应该是用来评估各种方法的工具。这些组成部分以另一种方式组织在一个项目中，该项目由美国国家科学基金会新兴前沿研究与创新部门和CBET部门的催化和生物催化项目联合授予给宾夕法尼亚州伯利恒利哈伊大学的Steven McIntosh、Bryan W. Berger、Robert Skibbens和Christopher J. Kiely教授以及纽约州锡拉丘兹锡拉丘兹大学的Ivan V. Korendovych教授组成的科学家和工程师团队。研究小组建议创造一种新型的生物合成酶-量子点混合光催化剂，用于直接从阳光、水和二氧化碳中生产甲醇燃料。该系统的关键组成部分包括(1)量子点（QDs）作为电子供体和(2)用于将CO2和水连续转化为MeOH的CO2还原酶。量子点对光子的吸收将产生电子-空穴激子对。这个空穴将被利用来分解水以形成质子，而电子将被用作酶促二氧化碳还原步骤的能量来源。这个酶促过程消耗由水分解形成的质子，完成催化循环。将这两种组分（量子点和酶）结合在拟议的连续流过程中，将为大规模生产可再生液体燃料创造一种具有成本效益的技术。量子点将使用一种独特的细菌系统来合成，这种系统有助于精确控制捕获光的粒径和相应的波长范围。与需要高温、高压和有毒溶剂的传统批量量子点化学合成相比，团队方法允许直接从培养上清液中直接生产水溶性量子点，其目标是通过消除复杂和昂贵的化学处理步骤，将这些材料的成本降低两个数量级。这对于实现成本效益高、可扩展的直接液体燃料生产解决方案至关重要。一个以酵母为基础的系统将被设计成连续产生三种酶，依次催化二氧化碳还原为甲醇。利用蛋白质工程方法，pi将修饰这些酶，使其在量子点表面自组装成异源三聚体复合物。这些自组装酶催化剂克服了目前对昂贵的贵金属基光催化剂的要求。此外，集成的酶- qd催化剂将通过消除与贵金属催化剂发生的非选择性副反应，实现所需液体燃料产品的高选择性。更广泛的影响：可扩展的光催化甲醇生产和低成本的量子点制造都对社会和美国经济产生了重大的长期影响。一种低成本的绿色燃料，利用二氧化碳、阳光和水在商业规模上连续生产，具有明显的潜力。量子点技术在信息技术、照明和医学中的应用目前受到这些专门的晶体纳米材料的高成本的限制。降低它们的生产成本有可能培育新的国内工业。同样，酶- qd混合纳米催化剂平台的模块化特性为从二氧化碳和阳光中可扩展合成其他高价值化学产品开辟了新的机会。

ABSTRACTIntellectual Merit: The focus of this solicitation was to develop concepts for a photosynthetic biorefinery, in which micro-organisms are employed in the conversion of sunlight and carbon dioxide (CO2) to produce biofuel and bioproduct species. A systems approach is needed, and the system should be scalable. Life cycle analysis should be a tool used to evaluate various approaches. These components have been organized in an alternative manner in a project awarded jointly by the NSF Emerging Frontiers in Research and Innovation Division and the Catalysis and Biocatalysis Program of the CBET Division to the team of scientists and engineers of Professors Steven McIntosh, Bryan W. Berger, Robert Skibbens and Christopher J. Kiely of Lehigh University, Bethlehem, PA, and Ivan V. Korendovych of Syracuse University, Syracuse, NY. The investigative team proposes to create a novel bio-synthesized enzyme-quantum dot hybrid photocatalyst for the direct production of methanol fuel from sunlight, water, and carbon dioxide. The key components of this system include (1) quantum dots (QDs) as electron donors and (2) CO2-reducing enzymes for continuous conversion of CO2 and water to MeOH. Absorption of photons by QDs will generate electron-hole exciton pairs. The hole will be harnessed for water splitting to form protons, while the electron will be utilized as the energy source for the enzymatic CO2 reduction steps. This enzymatic process consumes the protons formed from water splitting, completing the catalytic cycle. Combining these two components (QDs and enzymes) in the proposed continuous flow process will create a cost-effective technology for the large-scale production of renewable liquid fuels.QDs will be synthesized using a unique bacterial system that facilitates precise control over particle size and corresponding wavelength range of the harvested light. In contrast to conventional, batch QD chemical synthesis, in which high temperatures, pressures and toxic solvents are required, the team approach allows for direct, extracellular production of water-soluble QDs directly from culture supernatants, with a target of reducing the cost of these materials by two orders of magnitude by removing the need for complex and expensive chemical processing steps, which is critical for achieving a cost-effective and scalable solution for direct liquid fuel production. A yeast-based system will be engineered to continuously generate the three enzymes that sequentially catalyze the reduction of carbon dioxide to methanol. Using a protein engineering approach, the PIs will modify these enzymes to self-assemble into a heterotrimeric complex on the surface of the quantum dot. These self-assembling enzyme catalysts overcome the current requirements for expensive precious metal based photocatalysts. Furthermore, the integrated enzyme-QD catalyst will achieve high selectivity for desired liquid fuel products by eliminating non-selective side reactions occurring with precious metal catalysts.Broader Impacts: Both scalable photocatalytic MeOH production and low cost QD fabrication offer significant long term impact on society and the US economy. A low cost, green fuel, produced continuously at commercial scale from carbon dioxide, sunlight, and water has obvious potential. The application of QD technology in information technology, lighting, and medicine is currently limited by the high cost of these specialized, crystalline nanomaterials. Reducing their production cost has the potential to foster new domestic industries. Likewise, the modular nature of the enzyme-QD hybrid nanocatalyst platform opens up new opportunities for scalable synthesis of other high-value chemical products from CO2 and sunlight.