Harvesting electricity with Geobacter bremensis isolated from compost

Area of Science:

• Microbial electrochemistry
• Biofilm engineering
• Environmental microbiology

Background:

• Electrochemically active (EA) biofilms are crucial for microbial anode applications.
• Understanding microbial community composition is vital for optimizing EA biofilm performance.
• Current microbial anodes often contain complex consortia with varying efficiencies.

Purpose of the Study:

• To characterize the microbial community of EA biofilms formed on dimensionally stable anode-type electrodes (DSA).
• To identify key bacterial genera responsible for electrochemical activity.
• To evaluate the potential of pure cultures for enhanced current density generation.

Main Methods:

• Formation of EA biofilms on DSA electrodes in garden compost.
• 16S rRNA gene library analysis to determine microbial community structure.
• Isolation and pure culture cultivation of dominant bacterial strains.
• Electrochemical performance testing of pure cultures and mixed biofilms using cyclic voltammetry and chronoamperometry.
• Fluorescence in situ hybridization (FISH) for in-situ community analysis.

Main Results:

• EA biofilms were significantly enriched in Deltaproteobacteria, particularly Pelobacter and Geobacter genera, compared to controls.
• Pure cultures of Geobacter bremensis isolates exhibited substantially higher current densities (up to 2490 mA/m(2)) than the original mixed biofilms (approx. 300 mA/m(2)).
• Pelobacter species, though predominant in the mixed biofilm, lacked electrochemically active (EA) capacity, explaining lower overall performance.

Conclusions:

• Geobacter bremensis is a key electrochemically active bacterium in compost-based biofilms.
• Pure culture isolation and utilization of specific EA strains, like G. bremensis, offer a promising strategy to improve microbial anode efficiency.
• Targeting and culturing dominant EA genera can overcome limitations of mixed-culture performance in bioelectrochemical systems.