Enhancement of bioelectricity generation by cofactor manipulation in microbial fuel cell

• Cofactor manipulation increased the intracellular NAD(H) pool.
• The nadE overexpression strain showed higher electrochemical activity.
• Overexpressing nadE decreased the charge transfer resistance of MFC.
• The electron shuttle (pyocyanin) production increased upon nadE overexpression.
• Metabolic engineering is of great potential for electricity power output improvement.

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/cm2 to 40.13 μW/cm2). 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.