The process begins with the bacteria consuming organic matter and breaking it down through their metabolism. During this process, the bacteria release electrons as a byproduct. These electrons are then captured by the anode of the MFC, which is in contact with the bacteria. The electrons travel through the external circuit of the MFC and are eventually accepted by the cathode, where they combine with oxygen to form water.
The overall chemical reaction can be simplified as:
Organic matter + Bacteria → Electrons (captured by anode)
Electrons (through external circuit) → Cathode + Oxygen → Water
As a result of this electron transfer, an electrical current is generated between the anode and the cathode. The voltage and power output of the MFC depend on various factors such as the type of bacteria, substrate concentration, and the efficiency of the system.
Here are some examples of cells that can convert chemical energy to make an electrical current using MFCs:
Shewanella oneidensis: This bacterium is commonly used in MFCs due to its high exoelectrogenic activity. Shewanella species can utilize various organic compounds and are found in aquatic environments.
Geobacter sulfurreducens: Another well-known exoelectrogenic bacterium, Geobacter, can transfer electrons to electrodes and utilize various substrates such as acetate and lactate.
Pseudomonas aeruginosa: Pseudomonas species have shown the ability to generate electricity in MFCs using organic substrates like glucose and acetate.
Escherichia coli: Although not as commonly used as the previously mentioned bacteria, certain strains of E. coli have been engineered to exhibit exoelectrogenic behavior.
These cells are notable for their ability to convert the chemical energy stored in organic compounds into electrical energy through the process of extracellular electron transfer. This capability opens up possibilities for bioenergy production and wastewater treatment applications, where MFCs can generate electricity while simultaneously treating organic pollutants.
