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Background on Microbial Fuel Cells • A bio-electric system – Microbially maintained ion gradient fuels electron flow, generating electricity • Two phases of microbial fuel cells – Degradation of organic matter (cellulose) – Electricity generation (transfers ions) Examples of Microbial Fuel Cells Background on MFCs • Mixed Cultured MFCs – Advantages: • Full, robust utilization of breakdown products • Wide range of functionality • Single Strain MFCs – Advantages: • Simplification of bio-component MFC • Better capacity for genetic engineering in MFCs Simultaneous Cellulose Degradation and Electricity Production by Enterobacter cloacae in a Microbial Fuel Cell Authors: Farzaneh Rezaei, Defeng Xing, Rachel Wagner, John M. Regan, Tom L. Richard, and Bruce E. Logan Penn State University Methods • Isolation by DTE (dilution to extinction) – Based on exoelectrogenartion and cellulose degradation • PCR (polymerase chain reaction), DGGE (denaturing gradient gel electrophoresis), and 16S rRNA sequence comparison • Biochemical comparison – Measured growth with various carbon sources Results • DGGE of dilution to extinction Results • Enterobacter cloacae – Gram-negative – Facultative anaerobe – Rod-shaped – Motile by peritrichous flagella Discussion • Enterobacter cloacae MFC is first single strained MFC. • This MFC is limited by complete metabolism and toxin accumulation. • Measuring exoelectrogeneration potential by Fe(III) reduction is flawed • Synergistic effects of mixed culture MFCs are poorly understood Comparison of electricity production Critique • Single wastewater source – One source limits the potential microbes. – Researchers should have isolated microbes from several sources. • Isolation and characterization was narrow – Other microbes from mixed cultures should have been examined closely to understand the mechanisms behind mixed culture synergy. References • Christy, A. D., 2008. Cellulose Conversion to Electricity in Microbial Fuel Cells: Challenges and Constraints. Microbial Fuel Cells First International Symposium • Rezaei, Farzaneh, et al. 2009. Simultaneous cellulose degradation and electricity production by Enterobacter cloacae in a Microbial Fuel Cell. Appl. Environ. Microbiol. 75:3673–3678 • Zuo, Y., et. al. 2008. Isolation of the exoelectrogenic bacterium Ochrobactrum anthropi YZ-1 by using a U-tube microbial fuel cell. Appl. Environ. Microbiol. 74:3130-3137 Questions?