Sampling natural biofilms: a new route to build efficient microbial anodes

Area of Science:

• Microbiology
• Electrochemistry
• Environmental Science

Background:

• Electrochemically active biofilms (EA-biofilms) are crucial for microbial anodes.
• Inoculum source significantly impacts biofilm performance.

Purpose of the Study:

• To investigate the efficacy of different inoculum sources for constructing efficient EA-biofilms.
• To optimize microbial anode performance using natural biofilms.

Main Methods:

• Construction of EA-biofilms on graphite anodes at -0.1 V vs SCE with acetate.
• Inoculation with natural biofilms, marine sediments, and beach sand.
• Characterization of bacterial communities using DGGE analysis.
• Optimization of acetate consumption and coulombic efficiency.

Main Results:

• Natural biofilm inoculum yielded significantly higher current densities (2.0 A/m2) compared to sediments (0.4 A/m2) and sand (0.8 A/m2).
• DGGE revealed distinct bacterial communities, with Bacteroidetes, Halomonas, and Marinobacterium found in efficient EA-biofilms.
• Coulombic efficiency improved from 31% to 89% after substrate adaptation.
• Maximal current density reached 7.9 A/m2 with graphite anodes.

Conclusions:

• Natural biofilms are a highly promising inoculum source for rapidly developing efficient microbial anodes.
• Optimized EA-biofilms demonstrate superior performance for acetate consumption and current generation.
• Graphite anodes show high efficiency, potentially due to surface roughness.