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

知识价值：本次征集的重点是开发光合作用生物精炼的概念，在光合作用生物精炼中，微生物被用于转化阳光和二氧化碳(CO2)以生产生物燃料和生物产品种类。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一种用于评估各种方法的工具。这些组成部分在一个由NSF新兴前沿研究与创新部门和CBET部门催化和生物催化计划联合授予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教授和纽约州锡拉丘兹大学的Ivan V.Korendovych教授的科学家和工程师团队中以另一种方式组织。研究小组建议创造一种新型的生物合成酶-量子点杂化光催化剂，用于直接从阳光、水和二氧化碳中生产甲醇燃料。该体系的关键组成部分包括(1)作为电子供体的量子点(Qds)和(2)二氧化碳还原酶，用于将二氧化碳和水连续转化为甲醇。量子点对光子的吸收会产生电子-空穴激子对。这个空穴将被利用来分解水形成质子，而电子将被用作酶促二氧化碳还原步骤的能源。这个酶过程消耗水分解形成的质子，完成催化循环。将这两种成分(量子点和酶)结合在拟议的连续流动过程中，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。量子点将使用独特的细菌系统合成，该系统有助于精确控制颗粒大小和对应的收获光波长范围。与需要高温、高压和有毒溶剂的常规批量量子点化学合成不同，团队方法允许直接从培养上清液中直接在细胞外生产水溶性量子点，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，这对于实现经济高效和可扩展的直接液体燃料生产解决方案至关重要。一个基于酵母的系统将被设计成连续产生三种酶，这些酶依次催化二氧化碳还原为甲醇。利用蛋白质工程的方法，PI将修饰这些酶，使其在量子点表面自组装成异三聚体复合体。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需求。此外，集成的酶-QD催化剂将通过消除贵金属催化剂发生的非选择性副反应，实现对所需液体燃料产品的高选择性。广泛影响：可扩展的光催化甲醇生产和低成本QD制造都对社会和美国经济产生重大的长期影响。一种低成本的绿色燃料，由二氧化碳、阳光和水连续商业规模生产，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特殊的、结晶的纳米材料高昂成本的限制。降低它们的生产成本有可能培育新的国内产业。同样，酶-QD杂化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.