Nanostructured Interfaces for Bioelectrocatalysis

脱氢酶催化氧化/还原反应，涉及底物和携带电子的辅因子之间的两个电子转移。该项目的目标是为生物电催化创造经济的脱氢酶电极。自然界中发现的脱氢酶的多样性和特异性为生产广泛的产品提供了潜力，包括手性糖、氨基酸、醇和类固醇，以及许多医药中间体和特种化学品。然而，由于酶和辅因子成本高，体积反应速率低，脱氢酶基生物电催化的突出商业潜力尚未实现。PIs计划通过创造纳米结构的酶电极来解决这些挑战，这些电极可以(a)利用嗜热细菌的脱氢酶提高酶的寿命，(b)通过表面固定增加酶的保留，以允许辅助因子和酶替代的方式，(c)通过在界面内保留辅助因子以及电化学再生来降低辅助因子的成本。(d)使用具有高效材料传输特性的超高表面积电极显著提高反应速率。该研究的技术目标是：(1)开发纳米结构的生物电子界面，在碳电极、电子介质、辅助因子和耐热脱氢酶之间实现有效的电子转移；(2)同时分析控制反应速率的传质、电子传递和反应动力学；(3)建立预测数学模型来设计和优化生物电催化电极。该模型系统将是利用来自超嗜热菌Thermotoga martima的甘露醇脱氢酶从葡萄糖生产甘露醇。多学科研究团队开发了设计、制造、表征和优化纳米结构生物电子界面所需的实验和建模工具，以实现经济高效的电化学辅因子再生。这项工作将整合这些能力，以发展对控制脱氢酶为基础的生物电催化界面的分子过程的基本理解，并为设计和优化工业应用的生物电催化反应器提供所需的知识基础。智力优势：该项目将阐明质量传递、电子传递和可逆酶动力学之间的复杂相互作用，这些相互作用决定了基于脱氢酶（最大的一类氧化还原酶）的生物电子界面的性能。将根据寿命、催化性能和活性范围来确定嗜热酶的影响。将开发新的界面结构，在碳电极和拴在一起的介质、辅因子和脱氢酶之间提供有效的多步电子转移。将探讨高表面积电极作为工业规模周转率途径的局限性。更广泛的影响：这些研究的结果将对美国工业将医药中间体、生物基化学品和各种其他化合物转化为高价值产品的能力产生广泛的影响。此外，这项工作将促进理工科学生在研究生、本科生和大学预科阶段的发展。实现这些目标的关键努力将包括：(1)为一项正在进行的、由美国国家科学基金会（nsf）赞助的面向城市中学生的推广计划做出贡献，让他们了解生物可再生产品和工艺对环境和能源的影响；(2)本科生参与由国家科学基金资助的以实验室为基础的多学科课程的研究；(3)培养具有工程和科学背景的定量生物学研究生。研究成果将通过会议报告、同行评议的出版物和项目网站传播。

CBET-0756703, WordenDehydrogenase enzymes catalyze oxidation/reduction reactions involving transfer of two electrons between the substrate and an electron-carrying cofactor. The goal of this project is to create economical dehydrogenase-based electrodes for bioelectrocatalysis. The diversity and specificity of dehydrogenases found in nature offers the potential to produce a wide range of products, including chiral sugars, amino acids, alcohols, and steroids, as well as many pharmaceutical intermediates and specialty chemicals. The outstanding commercial potential of dehydrogenase-based bioelectrocatalysis has not yet been realized, though, due to high enzyme and cofactor costs and low volumetric reaction rates. The PIs plan to address these challenges by creating nanostructured enzyme electrodes that (a) improve enzyme lifetime using dehydrogenases from thermophilic bacteria, (b) increase enzyme retention via surface immobilization in a manner that allows facile cofactor and enzyme replacement, (c) reduce cofactor costs by cofactor retention within the interface coupled with electrochemical regeneration, and (d) dramatically amplify reaction rates using ultra-high surface area electrodes with efficient material transport properties.The technical objectives of the research are to (1) develop nanostructured bioelectronic interfaces that achieve efficient electron transfer between a carbon electrode, an electron mediator, a cofactor, and a thermostable dehydrogenase; (2) analyze the simultaneous mass-transfer, electron transfer, and reaction kinetics that govern the reaction rate; and (3) develop predictive mathematical models to design and optimize electrodes for bioelectrocatalysis. The model system will be mannitol production from glucose using the mannitol dehydrogenase from the hyperthermophile Thermotoga maritima.The multidisciplinary research team has developed experimental and modeling tools needed to design, fabricate, characterize, and optimize nanostructured bioelectronic interfaces to achieve cost-effective electrochemical cofactor regeneration. This work would integrate these capabilities to develop a fundamental understanding of the molecular processes governing dehydrogenase-based bioelectrocatalytic interfaces and provide the knowledge base needed to design and optimize electrobiocatalytic reactors for industrial applications.Intellectual Merit: This project will elucidate the complex interactions between mass transfer, electron transfer, and reversible enzyme kinetics that govern the performance of bioelectronic interfaces based on dehydrogenases, the largest class of oxidoreductase enzymes. The impact of thermophilic enzymes will be determined, in terms of lifetime, catalytic performance, and activity range. Novel interface architectures will be developed that give efficient multi-step electron transfer between carbon electrodes and tethered mediators, cofactors, and dehydrogenases. The limits of high-surface area electrodes as a route to industrial-scale turnover rates will be explored.Broader Impacts: The results of these studies will have broad impact on the ability of US industries to convert pharmaceutical intermediates, biobased chemicals, and a variety of other compounds into high-value products. In addition, the work will enhance the development of science and engineering students at the graduate, undergraduate, and precollege levels. Key efforts toward these goals will include (1) contributing to an ongoing, NSF-sponsored outreach program to urban youth of middle school age, to expose them to the environmental and energy impact of biorenewable products and processes; (2) participation in the research by undergraduate students as part of a laboratory-based, multidisciplinary course developed with NSF funding; and (3) training graduate students with engineering and science backgrounds in quantitative biology. Research results will be disseminated via conference presentations, peer-reviewed publications, and a project website.