Bioelectrochemical reactor

A Bioelectrochemical reactor is a type of bioreactor where bioelectrochemical processes are used to degrade/produce organic materials using microorganisms. This bioreactor has two compartments: The anode, where the oxidation reaction takes place; And the cathode, where the reduction occurs. At these sites, electrons are passed to and from microbes to power reduction of protons, breakdown of organic waste, or other desired processes. They are used in microbial electrosynthesis, environmental remediation, and electrochemical energy conversion. Examples of bioelectrochemical reactors include microbial electrolysis cells, microbial fuel cells, enzymatic biofuel cells, electrolysis cells, microbial electrosynthesis cells, and biobatteries. Electron current is inherent to microbial metabolism. Microorganisms transfer electrons from an electron donor (lower potential species) to an electron acceptor (higher potential species). If the electron acceptor is an external ion or molecule, the process is called respiration. If the process is internal, electron transfer is called fermentation. The microorganism attempts to maximize their energy gain by selecting the electron acceptor with the highest potential available. In nature, mainly minerals containing iron or manganese oxides are reduced. Often soluble electron acceptors are depleted in the microbial environment. The microorganism can also maximize their energy by selecting a good electron donor that can be easily metabolized. These processes are done by extracellular electron transfer (EET). The theoretical free energy change (ΔG) for microorganisms relates directly to the potential difference between the electron acceptor and the donor. However, inefficiencies like internal resistance will decrease this free energy change. The advantage of these devices is their high selectivity in high speed processes limited by kinetic factors. The most commonly studied species are Shewanella oneidensis and Geobacter sulfurreducens. However, more species have been studied in recent years.

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