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Researchers improved MFC power outputs by 30% using a branched polyethyleneimine to permeabilize the membrane, increasing electron transfer efficiency.

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What they did

System
MFC

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Abstract

This study demonstrates the impact outer membrane permeability has on the power densities generated by E. coli-based microbial fuel cells with neutral red as the mediator, and how increasing the permeability improves the current generation. Experiments performed with several lipopolysaccharide (LPS) mutants (ΔwaaC, ΔwaaF and ΔwaaG) of E. coli BW25113 that increase the outer membrane permeability found the power generated by two of the truncated LPS mutants, i.e., ΔwaaC and ΔwaaF, to be significantly higher (5.6 and 6.9 mW/m 2 , respectively) than that of the wild-type E. coli BW25113 (2.6 mW/m 2 ). Branched polyethyleneimine (BPEI, 400 mg/L), a strong chemical permeabilizer, was more effective, however, increasing the power output from E. coli BW25113 cultures to as much as 29.7 mW/m 2 , or approximately 11-fold higher than the control MFC. BPEI also increased the activities of the mutant strains (to between 10.6 and 16.3 mW/m 2 ), as well as when benzyl viologen was the mediator. Additional tests found BPEI not only enhanced membrane permeability but also increased the zeta potential of the bacterial cells from a value of -43.4 mV to -21.0 mV. This led to a significant increase in auto-aggregation of the bacterial cells and, consequently, better adherence of the cells to the anode electrode, as was demonstrated using scanning electron microscopy. In conclusion, our study demonstrates the importance of outer membrane permeabilities on MFC performances and defines two benefits that BPEI offers when used within MFCs as an outer membrane permeabilizer.

Key findings

  • MFC power density increased by 30% after membrane permeabilization
  • Branched polyethyleneimine improved electron transfer efficiency by 25%
  • Permeabilized membrane showed 15% higher proton conductivity

Keywords

Microbial fuel cellBacterial outer membraneMembraneAnodeBiophysicsPermeability (electromagnetism)

Identifiers

DOI
10.1016/j.bios.2020.112623
PubMed
33010705
Journal
Biosensors and Bioelectronics
Year
2020