Biochemical and Molecular Characterization of Soil-Isolated Exoelectrogens and Evaluation of Their Electrochemical Properties via Single-Chambered Mediator-Free Microbial Fuel Cell

Abstract

Microbial fuel cells are utilized in electromicrobiology for the purpose of cleaning wastewater and producing electricity. Anaerobically, MFCs use microbial catalysis in the anodic compartment to transform the chemical energy stored in organic and inorganic molecular bonds. Using the soil sample, four exoelectrogens are isolated. Each of the four single-chambered mediator-less microbial fuel cell design are used to inject the extracted soil exoelectrogens. A nutritional medium is used to operate the reactors in batches of 15 days. The exoelectrogen ISO4 (Bacillus amyloliquefaciens strain NSB4), followed by ISO3 (cereus strain BXC6), ISO2 (Bacillus sp. (in: Bacteria) strain 4N), and ISO1 (Staphylococcus argenteus strain D7) achieve the best growth rates. On average, data on energy generation shows that MFCs with ISO4 have the maximum voltage and power density at 1024 mV external resistance (1 kΩ), followed by ISO3 at 609 mV, ISO2 at 560  mV, and ISO1 at 487 mV. Power densities of isolates are recorded as: 41.281 mW/m², 29.241, 12.723, and 3.552 mW/m² for ISO4, ISO3, ISO2, and ISO1, respectively. The research finds that the energy output of MFC reactors is affected by the exoelectrogen substrates. Cyclic voltammetry (CV) experiment demonstrates that exoelectrogens directly transport electrons to the anode surface via cytochromes and other substances associated with the cell membrane. It has been previously difficult to produce power from pure isolates, but new research reveals that this is no longer an issue. Pure cultures of exolectrogens use to generate current also show a broad substrate utilization spectrum, in line with previous studies.