Department of Chemistry , University of Utah , 315 South 1400 East, Room 2020 , Salt Lake City , Utah 84112 , United States.
J Am Chem Soc. 2020 Feb 26;142(8):4028-4036. doi: 10.1021/jacs.9b13968. Epub 2020 Feb 12.
Enzymatic electrosynthesis is a promising approach to produce useful chemicals with the requirement of external electrical energy input. Enzymatic fuel cells (EFCs) are devices to convert chemical energy to electrical energy via the oxidation of fuel at the anode and usually the reduction of oxygen or peroxide at the cathode. The integration of enzymatic electrosynthesis with EFC architectures can simultaneously result in self-powered enzymatic electrosynthesis with more valuable usage of electrons to produce high-value-added chemicals. In this study, a H/α-keto acid EFC was developed for the conversion from chemically inert nitrogen gas to chiral amino acids, powered by H oxidation. A highly efficient cathodic reaction cascade was first designed and constructed. Powered by an applied voltage, the cathode supplied enough reducing equivalents to support the NH production and NADH recycling catalyzed by nitrogenase and diaphorase. The produced NH and NADH were reacted in situ with leucine dehydrogenase (LeuDH) to generate l-norleucine with 2-ketohexanoic acid as the NH acceptor. A 92% NH conversion ratio and 87.1% Faradaic efficiency were achieved. On this basis, a H-powered fuel cell with hyper-thermostable hydrogenase (SHI) as the anodic catalyst was combined with the cathodic reaction cascade to form the H/α-keto acid EFC. After 10 h of reaction, the concentration of l-norleucine achieved 0.36 mM with >99% enantiomeric excess and 82% Faradaic efficiency. From the broad substrate scope and the high enzymatic enantioselectivity of LeuDH, the H/α-keto acid EFC is an energy-efficient alternative to electrochemically produce chiral amino acids for biotechnology applications.
酶电化学合成是一种很有前途的方法，可以在外加电能输入的情况下生产有用的化学品。酶燃料电池（EFC）是一种通过在阳极氧化燃料，通常在阴极还原氧气或过氧化物，将化学能转化为电能的装置。将酶电化学合成与 EFC 结构集成可以同时实现自供电的酶电化学合成，从而更有效地利用电子生产高附加值化学品。在这项研究中，开发了一种 H/α-酮酸 EFC，用于将化学惰性氮气转化为手性氨基酸，由 H 氧化提供动力。首先设计并构建了一个高效的阴极反应级联。在施加电压的作用下，阴极提供足够的还原当量，以支持固氮酶和黄递酶催化的 NH 生成和 NADH 循环。生成的 NH 和 NADH 在原位与亮氨酸脱氢酶（LeuDH）反应，以 2-酮己酸作为 NH 受体生成 l-正亮氨酸。实现了 92%的 NH 转化率和 87.1%的法拉第效率。在此基础上，将具有超耐热氢化酶（SHI）的 H 燃料电池与阴极反应级联相结合，形成 H/α-酮酸 EFC。反应 10 小时后，l-正亮氨酸的浓度达到 0.36mM，对映体过量大于 99%，法拉第效率为 82%。由于 LeuDH 的广泛底物范围和高酶手性选择性，H/α-酮酸 EFC 是一种用于生物技术应用的电化学生产手性氨基酸的节能替代方法。
