Nanostructured Bioelectronic Interfaces

Non-Technical Summary: Redox enzymes carry out oxidation and reduction reactions that can convert biobased raw materials into high-value products. Industrial application of redox enzymes is limited by factors including (1) low enzyme stability outside of a limited range of temperature and pH, (2) high cost of producing and purifying the enzymes, and (3) inefficient coupling of the enzymes to electrodes and other molecules that participate in the reaction (e.g., cofactors). This project is designed to address these limitations. Highly stable redox enzymes will be produced using DNA isolated from microbes that grow at high temperature. These enzymes will be used to produce novel interfaces that provide efficient electrical communication between the redox enzymes, electrodes, cofactors, and other molecules. The resulting bioelectronic interfaces will be used in novel biosensors and electrochemical bioreactors that produce high-value products. <P> Approach: Dehydrogenase enzymes catalyze oxidation/reduction reactions involving transfer of two electrons between the substrate and an electron-carrying cofactor. This proposal seeks 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 biosensors, food components, and biobased chemicals, including chiral sugars, amino acids, alcohols, and steroids, and pharmaceutical intermediates. 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. 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. Thermophilic enzymes will be used to enhance the interface's 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. The results of these studies will have broad impact on the ability of US industries to produce high-value biobased foods and chemicals. Research results will be disseminated via conference presentations, peer-reviewed publications, and a project website.