Biology Reference
In-Depth Information
Chapter 1
Huijie Hou, Lei Li, Younghak Cho, Paul de Figueiredo, and Arum Han
INTRODUCTION
Microbial fuel cells (MFCs) are remarkable “green energy” devices that exploit
microbes to generate electricity from organic compounds. The MFC devices currently
being used and studied do not generate sufficient power to support widespread and
cost-effective applications. Hence, research has focused on strategies to enhance the
power output of the MFC devices, including exploring more electrochemically ac-
tive microbes to expand the few already known electricigen families. However, most
of the MFC devices are not compatible with high throughput screening for finding
microbes with higher electricity generation capabilities. Here, we describe the devel-
opment of a microfabricated MFC array, a compact and user-friendly platform for the
identification and characterization of electrochemically active microbes. The MFC
array consists of 24 integrated anode and cathode chambers, which function as 24 in-
dependent miniature MFCs and support direct and parallel comparisons of microbial
electrochemical activities. The electricity generation profiles of spatially distinct MFC
chambers on the array loaded with
Shewanella oneidensis
MR-1 differed by less than
8%. A screen of environmental microbes using the array identified an isolate that was
related to
Shewanella putrefaciens
IR-1 and
Shewanella
sp. MR-7, and displayed 2.3-
fold higher power output than the
S. oneidensis
MR-1 reference strain. Therefore, the
utility of the MFC array was demonstrated.
The MFCs are devices that generate electricity from organic compounds through
microbial catabolism [1-3]. A typical MFC contains an anaerobic anode chamber and
an aerobic cathode chamber separated by a proton exchange membrane (PEM), and
an external circuit connects the anode and the cathode [4, 5]. Electrochemically active
microbes (“electricigens”) reside within the anaerobic anode chamber. Electrons, gen-
erated during microbial oxidization of organic compounds, are delivered to the MFC
anode via microbial membrane-associated components [3, 6], soluble electron shuttles
[7, 8], or nanowires [9, 10]. Biofi lms that support close physical interactions between
microbial membranes and anode surfaces are also important for MFC power output
[11]. Electrons fl ow from the anode to the cathode through the external electrical cir-
cuit. In parallel, protons generated at the anode diffuse through the PEM and join the
electrons released to the catholyte (e.g., oxygen, ferricyanide) at the cathode chamber
[1]. This electron transfer event completes the circuit.
The MFCs have generated signifi cant excitement in the bioenergy community
because of their potential for powering diverse technologies, including wastewater
treatment, and bioremediation devices [12, 13], autonomous sensors for long-term
operations in low accessibility regions [14, 15], mobile robot/sensor platforms [16],