The effect of central metabolic activity of Escherichia coli cells acting as biocatalysts on the performance of microbial fuel cells (MFCs) was studied with glucose used as the energy source. Milliliter-scale two-chambered MFCs were used with 2-hydroxy-1,4-naphthoquinone (HNQ) as an electron mediator. Among the single-gene deletions examined, frdA, pdhR, ldhA, and adhE increased the average power output of the constructed MFC. Next, multiple-gene knockout mutants were constructed using P1 transduction. The Δ5 (ΔfrdAΔpdhRΔldhAΔadhEΔpta) strain showed the highest ave. power output (1.82 mW) and coulombic efficiency (21.3%). Our results show that the combination of multiple-gene knockout in E. coli cells leads to the development of an excellent catalyst for MFCs. Finally, preventing a decrease in the pH of the anodic solution was a key factor for improving the power output of the Δ5 strain, and a maximum ave. power output of 2.21 mW was achieved with 5% NaHCO3 in the buffer. The ave. power density of the constructed MFC was 0.27 mW/cm3, which is comparable to an enzymatic fuel cell of a Milliliter-scale using glucose dehydrogenase.
