Department of Chemistry and Chemical Biology , Harvard University , 12 Oxford Street , Cambridge , Massachusetts 02138-2902 , United States.
Acc Chem Res. 2019 Nov 19;52(11):3143-3148. doi: 10.1021/acs.accounts.9b00380. Epub 2019 Oct 8.
Sunlight is an abundant energy source for a sustainable society. Indeed, photosynthetic organisms harness solar radiation to build the world around us by synthesizing energy-rich compounds from water and CO. However, numerous energy conversion bottlenecks in the natural system limits the overall efficiency of photosynthesis; the most efficient plants do not exceed solar storage efficiencies of 1%. Artificial photosynthetic solar-to-fuels cycles may occur at higher intrinsic efficiencies, but they typically terminate at hydrogen, with no process installed to complete the cycle for carbon fixation. This limitation may be overcome by interfacing solar-driven water splitting to H-oxidizing microorganisms. To this end, hybrid biological-inorganic constructs have been created to use sunlight, air, and water as the only starting materials to accomplish carbon fixation in the form of biomass and liquid fuels. This artificial photosynthetic cycle begins with the Artificial Leaf, which accomplishes the solar process of natural photosynthesis-the splitting of water to hydrogen and oxygen using sunlight-under ambient conditions. To create the Artificial Leaf, an oxygen evolving complex of Photosystem II was mimicked, the most important property of which was the self-healing nature of the catalyst. Self-healing catalysts permit water splitting to be accomplished using any water source, which is the critical development for (1) the Artificial Leaf, as it allows for the facile interfacing of water splitting catalysis to materials such as silicon, and (2) the hybrid biological-inorganic construct, called the Bionic Leaf, as it allows for the facile interfacing of water splitting catalysis to bioorganisms. Hydrogenases in the bioorganism allow the hydrogen to be coupled to NADPH and ATP production, thus allowing the solar energy from water splitting to be converted into cellular energy to drive cellular biosynthesis. In the design of the hybrid system, water splitting catalysts must be designed that support hydrogen generation at low applied potential to ensure a high energy efficiency while avoiding reactive oxygen species. Using the tools of synthetic biology, a bioengineered bacterium, , converts carbon dioxide from air, along with the hydrogen produced from such catalysts of the Artificial Leaf, into biomass and liquid fuels, thus closing an entire artificial photosynthetic cycle. The Bionic Leaf operates at solar-to-biomass and solar-to-liquid fuels efficiencies that greatly exceed the highest solar-to-biomass efficiencies of natural photosynthesis.
阳光是可持续社会的丰富能源。事实上，光合作用生物利用太阳辐射通过将水和 CO 合成富含能量的化合物来合成我们周围的世界。然而，自然系统中存在许多能量转换瓶颈，限制了光合作用的整体效率；最有效的植物的太阳能存储效率不超过 1%。人工光合作用太阳能到燃料循环可能以更高的内在效率发生，但它们通常以氢气结束，没有安装任何过程来完成碳固定的循环。通过将太阳能驱动的水分解与 H 氧化微生物接口，可以克服这一限制。为此，已经创建了混合生物-无机构建体，以利用阳光、空气和水作为唯一起始材料，以生物质和液体燃料的形式完成碳固定。这个人工光合作用循环从人工叶子开始，它在环境条件下完成了自然光合作用的太阳能过程——利用阳光将水分解为氢气和氧气。为了创建人工叶子，模拟了光合作用系统 II 的放氧复合物，该复合物最重要的性质是催化剂的自修复性质。自修复催化剂允许使用任何水源完成水分解，这对于（1）人工叶子是至关重要的发展，因为它允许水分解催化与硅等材料的方便接口，（2）混合生物-无机构建体，称为仿生叶子，因为它允许水分解催化与生物有机体的方便接口。生物有机体中的氢化酶允许氢气与 NADPH 和 ATP 产生耦合，从而允许将水分解的太阳能转化为细胞能量以驱动细胞生物合成。在混合系统的设计中，必须设计支持在低施加电势下产生氢气的水分解催化剂，以确保高能量效率，同时避免活性氧物种。利用合成生物学的工具，一种经过生物工程改造的细菌，将空气中的二氧化碳与人工叶子等催化剂产生的氢气一起转化为生物质和液体燃料，从而完成整个人工光合作用循环。仿生叶子的太阳能到生物质和太阳能到液体燃料的效率远远超过自然光合作用的最高太阳能到生物质效率。
