A microbial fuel cell (MFC) uses bacteria to break down organic compounds found in waste water and generate an electric current. This is a sustainable way to generate power from waste material, with the potential of achieving over 50% energy efficiency. Our project will focus on genetically engineering the bacteria Shewanella oneidensis in ways that will make the microbial fuel cell more efficient.

According to the 2013 International Energy Outlook, energy demands will increase 56% by 2040. This rapidly growing demand for energy has sparked a search for sustainable and renewable energy sources. While many technologies are being developed to address this, some of the most intriguing are bioelectrochemical systems like the microbial fuel cell (MFC). The distinctiveness of bioelectrochemical systems come from their ability to simultaneously take on two ecological vices with: sustainable energy production, and waste-water treatment. The basics of how bacteria in an MFC produce electricity are understood, however we feel more research needs to be done to increase efficiency at the microbial level.

The most popular research for microbial fuel cells has been poised towards increasing the power density using more state-of-the-art synthetic materials in the structural design. Our project will focus on another aspect: modifying the microbes which are responsible for generating the electricity. Many of the current limiting factors of MFC performance comes from the bacteria themselves. We plan to address these factors with our two project goals.

The first and most apparent limiting factor in an MFC is the surface area of the anode. The bacteria can only generate electricity when it is in direct contact with, or in close proximity to the surface of the anode. To take full advantage of the limited surface area, it is best for the bacteria to grow in a dense film called a biofilm. This leads to our first goal:

1. 1. Increase biofilm growth rate of Shewanella oneidensis on the MFC anode.

We will also focus on the bacteria's ability to transfer electrons from the compounds in the waste water to the anode. There are many pathways which the bacteria can use to facilitate this, however studies have shown that Shewanella does not utilize them in the most efficient way. Much of inefficiency is due to the generation an excretion of Acetate. This is our second goal:

References

1. Korneel Rabaey, ed. Bioelectrochemical systems: from extracellular electron transfer to biotechnological application. IWA publishing, 2010.
2. Franks, Ashley E., and Kelly P. Nevin. "Microbial fuel cells, a current review." Energies 3.5 (2010): 899-919.
3. Brutinel ED, Gralnick JA. Anomalies of the anaerobic tricarboxylic acid cycle in Shewanella oneidensis revealed by Tn-seq. Mol Microbiol. 2012 Oct;86(2):273-83. doi: 10.1111/j.1365-2958.2012.08196.x. Epub 2012 Aug 27. PubMed PMID: 22925268.
4. Papagianni M. Recent advances in engineering the central carbon metabolism of industrially important bacteria. Microb Cell Fact. 2012 Apr 30;11:50. doi: 10.1186/1475-2859-11-50. Review. PubMed PMID: 22545791; PubMed Central PMCID: PMC3461431
5. Rabaey K, Verstraete W. Microbial fuel cells: novel biotechnology for energy generation. Trends Biotechnol. 2005 Jun;23(6):291-8. Review. PubMed PMID: 15922081.
6. Beliaev, Alex S., et al. "Gene and protein expression profiles of Shewanella oneidensis during anaerobic growth with different electron acceptors." Omics: a journal of integrative biology 6.1 (2002): 39-60.
7. Thormann, Kai M., et al. "Control of formation and cellular detachment from Shewanella oneidensis MR-1 biofilms by cyclic di-GMP." Journal of Bacteriology 188.7 (2006): 2681-2691.

Additional Resources

(Referred to in Abstract)

1. 8. Ching, Leang, and Nikhil S. Malvankar. "Engineering Geobacter Sulffureducens to Produce a Highly Cohesive Conductive Matrix with Enhanced Capacity for Current Production." Energy and Environmental Science (2013): 1901-908. Web.