Initial development and structure of biofilms on microbial fuel cell anodes

Area of Science:

• Microbiology
• Electrochemistry
• Bioengineering

Background:

• Microbial fuel cells (MFCs) utilize electrochemically active bacteria for energy conversion.
• Biofilm formation on electrodes is crucial for extracellular electron transfer (EET).
• Current understanding of EET primarily focuses on Gram-negative bacteria.

Purpose of the Study:

• Investigate bacterial biofilm formation in MFCs.
• Determine how biofilm development, structure, and viability impact electron transfer.
• Explore the role of Gram-positive bacteria in MFCs.

Main Methods:

• Pure and co-culture experiments with bacteria in MFCs.
• Monitoring biofilm viability under open and closed circuit conditions.
• Measuring power output and biofilm structure.

Main Results:

• Biofilm viability varied based on anode circuit conditions.
• Pseudomonas aeruginosa biofilms were thinner under closed circuit operation.
• Co-cultures of Gram-positive (Enterococcus faecium) and Gram-negative bacteria significantly increased power output (30-70%).
• Co-culture biofilms exhibited segregation, with P. aeruginosa forming towers through E. faecium.

Conclusions:

• Bacterial segregation in co-culture biofilms may represent different strategies for electron transfer and substrate capture.
• Gram-positive bacteria contribute to MFC performance, particularly in co-culture systems.