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Protein Engineering and Metabolic Modeling of Biofuel Cells

It is becoming increasingly clear that our current global reliance on petroleum for transportation and other energy needs is not sustainable. As we explore other energy sources to meet ever rising energy demands, we will also need to explore new energy carriers and energy distribution systems. Fuel cells offer significant advantages in that they have the potential to convert chemical energy directly to electrical energy with minimal environmental impact. A standard fuel cell consists of an anode and a cathode, such that electrons are extracted from the fuel using a catalyst on the anodic side, and after passing through the external electrical circuit, they are combined with oxygen using a catalyst on the cathodic side, resulting in the production of water. Ideally, the catalysts should be robust, stable, specific, and highly active. Precious-metal based catalysts are very stable and active, but their use can be hampered by specificity issues. On the other end of the spectrum, the most specific and active catalysts known are enzymes, but these biological molecules do not have the stability of metal catalysts. Enzymes have already been naturally evolved to promote the transfer of electrons between substrates with an exquisite level of specificity. Unfortunately, they have not been evolved to operate in biofuel cells, and thus they will need to be further engineered in order to perform in this artificial environment.

We are working on engineering improved enzymes for use in biofuel cells. We are collaborating with Susan Brozik at Sandia National Labs to make improved Glucose Oxidase (GOx) enymes using rational design approaches. We have been able to site-specifically attach gold nanoparticles to GOx mutants to improve direct electron transfer. We are also collaborating with Alfonso Jaramillo at Ecole Polytechnique to use computational design to make novel laccase enzymes. We are also working with Plamen Atanassov at the University of New Mexico to engineer laccase enzymes that bind DNA so they can be immobilized in a site-specific manor determined by specific DNA sequences.

We are also developing elaborate kinetics-based models of biofuel cells. These models can be used to assess the performance of new enzymes in biofuel cells under different operating conditions, and they can provide insight into the rate limiting steps and processes in the operation of the biofuel cell. For example, oxygen is the terminal electron acceptor for the biofuel cell, and therefore it is a required substrate for the laccase enzyme on the biofuel cell cathode. But, oxygen is also a natural substrate for the glucose oxidase enzyme on the biofuel cell anode, and this enzyme can divert enzymes from the external electrical circuit, and use them to reduce oxygen to hydrogen peroxide. Therefore, high concentrations of oxygen will simultaneously enhance cathodic performance and limit anodic performance. Our kinetics based models will be used to identify optimal operating conditions to achieve maximal biofuel cell performance. As these models are developed, they will be combined with existing transport-based models in order to create a complete in silico model of enzymatic biofuel cells.

Related Publications

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  1. Error fetching PMID 22050076: [Paper6]
  2. Error fetching PMID 21541425: [Paper5]
  3. Error fetching PMID 21541425: [Paper4]
  4. Error fetching PMID 19061242: [Paper3]
  5. Error fetching PMID 18824691: [Paper2]
  6. Error fetching PMID 18096378: [Paper1]
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