Dr. Scott Crittenden
Army Research Laboratory
Electrogenic Bacteria: Microbial Fuel Cells and Chemoelectric Biosensors
Monday, February 26, 2007
Bacteria capable of anaerobic respiration need a replacement for oxygen to serve as an electron acceptor. It has recently become clear that there are several genera which are capable of using macroscopic metallic electrodes for this purpose. A microbial fuel cell (MFC) is a power generation device that utilizes these bacteria to directly oxidize organic fuel and deliver free electrons to an anode. This power generation ability coupled with the high energy conversion efficiency of some of these organisms and the wide range of acceptable electron donors, e.g. glucose, cellulose, wastewater, etc., raises interesting possibilities for the development of green renewable energy sources. Also, since the electrical current produced is a byproduct of normal metabolism, its behavior over time under changing environmental circumstances (consumption of food, etc.) can serve as a direct, electrical, measurement of metabolic rate, in effect rendering the bacterium not just a sensor but a transducer as well.
Details of the mechanisms by which electrons are liberated within and transferred from these organisms are not well understood nor is the range of possible energy sources or maximum potential power generation. I present our results regarding the ability to controllably enhance or reduce current production via alkanethiol self-assembled monolayer modified anodes. In addition, I discuss experiments elucidating the effect of electron mediators on generated current as well as bacterial fermentation end-products.