Enhancement of bioelectricity generation by cofactor manipulation in microbial fuel cell

Microbial fuel cells (MFCs) are promising for harnessing bioenergy from various organic wastes. However, low electricity power output (EPT) is one of the major bottlenecks in the practical application of MFCs. In this study, EPT improvement by cofactor manipulation was explored in the Pseudomonas aeruginosa-inoculated MFCs. By overexpression of nadE (NAD synthetase gene), the availability of the intracellular cofactor pool (NAD(H/(+))) significantly increased, and delivered approximately three times higher power output than the original strain (increased from 10.86 μW/cm(2) to 40.13 μW/cm(2)). The nadE overexpression strain showed about a onefold decrease in charge transfer resistance and higher electrochemical activity than the original strain, which should underlie the power output improvement. Furthermore, cyclic voltammetry, HPLC, and LC-MS analysis showed that the concentration of the electron shuttle (pyocyanin) increased approximately 1.5 fold upon nadE overexpression, which was responsible for the enhanced electrochemical activity. Thus, the results substantiated that the manipulation of intracellular cofactor could be an efficient approach to improve the EPT of MFCs, and implied metabolic engineering is of great potential for EPT improvement.