Banta:Electrofuels: Difference between revisions

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[[Image:Electrofuel.jpg|thumb|400px|right|Crystal structure of a folded Beta Roll domain where the red spheres indicate the bound Ca+2 ions and the purple resides are randomized for molecular recognition (Dooley, Kim, Lu, Tu, and Banta, 2012 Biomacromolecules).]]
[[Image:Electrofuel.jpg|thumb|400px|right|Process diagram of the electrofuels process.  In the electrochemical reactor, ferric iron is reduced to ferrous iron.  This is fed to the biochemical reactor where genetically modified iron-oxidizing cells (Acidithiobacillus ferrooxidans) are able to produce chemicals or fuels from CO2.  This process provides a means to convert renewable energy (such as solar) to liquid fuels and chemicals.]]




'''Fuels and Chemicals from CO2 and electricity - Electrofuels'''  
'''Fuels and Chemicals from CO2 and electricity - Electrofuels'''  


Molecular recognition is ubiquitous in nature.  Frequently antibodies are used in technology applications where biomolecular recognition is to be employed, but antibodies have several limitations in these applications, including difficulty in easily removing bound targets.  This becomes especially important in the development of biosensors using electrochemical-based signal transduction schemes.
There is a clear need for the development of new strategies for sustainable fuel and chemical production. There is a great deal of interest in biofuels, which are produced using organisms (heterotrophs) that transform organic materials, such as sugars, into fuels such as ethanol.  These organic feedstocks are obtained from large-scale agriculture via photosynthesis. However, this approach is intrinsically limited by the low energy capture and transfer efficiency of photosynthesis as well as land and water usage issues. Autotrophic bacteria (which are able to directly utilize CO2 as a carbon source) have recently attracted attention as potentially sustainable biosynthetic platforms for chemical production as autotrophs do not require organic compounds and thus do not involve agriculture.


Instead of trying to engineer allosteric control into a molecular recognition molecule, we have started with intrinsically disordered scaffold, the beta roll domain, and we are working to evolve this allosterically regulated scaffold for biomolecular recognition.  The naturally existing beta roll subdomain motif consists of tandem repeats of the sequence GGXGXDXUX, where U is an aliphatic amino acid and X is any amino acid. In the presence of calcium, the disordered peptide reversibly transitions to a beta roll spiral structure of two parallel beta sheet faces, where each beta strand has two solvent exposed variable residues.  
We are developing an "electrofuels" process which consists of an electrochemical reactor that reduces a mediator molecule which can subsequently deliver electrons to microbes within a bioreactor.  In our approach, we have chosen to use iron as the mediator and we have identified a unique bacterium, Acidithiobacillus ferrooxidans, which can grow by oxidizing iron using CO2 as a carbon source.  We have developed novel reactor designs and medium formulations to grow the cells efficiently in the electrofuels platform.  And, we have developed a genetic system for the bacterium so we can introduce foreign metabolic pathways into the cells to enable them to produce new fuels and chemicals.  The net result of this platform is the production of chemicals and fuels from electricity and air, and this could be a pathway forward for eventually producing transportation fuels from CO2 and renewable energy (such as solar).


We have characterized a native beta roll subdomain with various end-capping groups in order to identify a minimal calcium-responsive beta roll unit.  We have immobilized the beta roll on surfaces, and we have developed a FRET-based system to monitor structural perturbations.  We have truncated and concatenated the beta roll and we have discovered beta roll sequences that can reversibly precipitate which is useful for protein purification.  We believe that the beta roll faces are suitable binding surfaces and that calcium-induced structure formation can be used as a mechanism to control the formation of the engineered biomolecular recognition interface.  To test this, we have engineered beta rolls to dimerize in a calcium-dependent manor and used these to create cross-links for protein hydrogels. We have randomized one face of the beta roll unit and we are using directed evolution to identify beta roll peptides with biomolecular recognition capabilities.


'''Related Publications'''
'''Related Publications'''

Revision as of 12:05, 17 July 2014

Banta Lab

Protein and Metabolic Engineering

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Process diagram of the electrofuels process. In the electrochemical reactor, ferric iron is reduced to ferrous iron. This is fed to the biochemical reactor where genetically modified iron-oxidizing cells (Acidithiobacillus ferrooxidans) are able to produce chemicals or fuels from CO2. This process provides a means to convert renewable energy (such as solar) to liquid fuels and chemicals.


Fuels and Chemicals from CO2 and electricity - Electrofuels

There is a clear need for the development of new strategies for sustainable fuel and chemical production. There is a great deal of interest in biofuels, which are produced using organisms (heterotrophs) that transform organic materials, such as sugars, into fuels such as ethanol. These organic feedstocks are obtained from large-scale agriculture via photosynthesis. However, this approach is intrinsically limited by the low energy capture and transfer efficiency of photosynthesis as well as land and water usage issues. Autotrophic bacteria (which are able to directly utilize CO2 as a carbon source) have recently attracted attention as potentially sustainable biosynthetic platforms for chemical production as autotrophs do not require organic compounds and thus do not involve agriculture.

We are developing an "electrofuels" process which consists of an electrochemical reactor that reduces a mediator molecule which can subsequently deliver electrons to microbes within a bioreactor. In our approach, we have chosen to use iron as the mediator and we have identified a unique bacterium, Acidithiobacillus ferrooxidans, which can grow by oxidizing iron using CO2 as a carbon source. We have developed novel reactor designs and medium formulations to grow the cells efficiently in the electrofuels platform. And, we have developed a genetic system for the bacterium so we can introduce foreign metabolic pathways into the cells to enable them to produce new fuels and chemicals. The net result of this platform is the production of chemicals and fuels from electricity and air, and this could be a pathway forward for eventually producing transportation fuels from CO2 and renewable energy (such as solar).


Related Publications

  1. Li X, Mercado R, Kernan T, West AC, and Banta S. Addition of citrate to Acidithiobacillus ferrooxidans cultures enables precipitate-free growth at elevated pH and reduces ferric inhibition. Biotechnol Bioeng. 2014 Oct;111(10):1940-8. DOI:10.1002/bit.25268 | PubMed ID:24771134 | HubMed [Paper2]
  2. Khunjar WO, Sahin A, West AC, Chandran K, and Banta S. Biomass production from electricity using ammonia as an electron carrier in a reverse microbial fuel cell. PLoS One. 2012;7(9):e44846. DOI:10.1371/journal.pone.0044846 | PubMed ID:23028643 | HubMed [Paper1]

All Medline abstracts: PubMed | HubMed

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