Microbial electrosynthesis (MES) is a form of microbial electrocatalysis in which electrons are supplied to living microorganisms via a

cathode A cathode is the electrode from which a conventional current leaves a polarized electrical device. This definition can be recalled by using the mnemonic ''CCD'' for ''Cathode Current Departs''. A conventional current describes the direction in whi ...

in an electrochemical cell by applying an

electric current An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving pa ...

. The electrons are then used by the microorganisms to reduce

carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...

to yield industrially relevant products. The electric current would ideally be produced by a renewable source of power. This process is the opposite to that employed in a

microbial fuel cell Microbial fuel cell (MFC) is a type of bioelectrochemical fuel cell system that generates electric current by diverting electrons produced from the microbial oxidation of reduced compounds (also known as fuel or electron donor) on the anode to oxid ...

, in which microorganisms transfer electrons from the oxidation of compounds to an anode to generate an electric current.

Comparison to microbial electrolysis cells

Microbial electrosynthesis (MES) is related to microbial electrolysis cells (MEC). Both use the interactions of microorganisms with a cathode to reduce chemical compounds. In MECs, an electrical power source is used to augment the

electrical potential The electric potential (also called the ''electric field potential'', potential drop, the electrostatic potential) is defined as the amount of work energy needed to move a unit of electric charge from a reference point to the specific point in ...

produced by the microorganisms consuming a source of chemical energy such as

acetic acid Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main component ...

. The combined potential provided by the power source and the microorganisms is then sufficient to reduce

hydrogen ion A hydrogen ion is created when a hydrogen atom loses or gains an electron. A positively charged hydrogen ion (or proton) can readily combine with other particles and therefore is only seen isolated when it is in a gaseous state or a nearly particle ...

s to molecular

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...

. The mechanism of MES is not well understood, but the potential products include alcohols and organic acids. MES can be combined with MEC in a single reaction vessel, where substrate consumed by the microorganisms provides a voltage potential that is lowered as the microbe ages. "MES has gained increasing attention as it promises to use renewable (electric) energy and biogenic feedstock for a bio-based economy."

Applications

Microbial electrosynthesis may be used to produce fuel from carbon dioxide using electrical energy generated by either traditional power stations or renewable electricity generation. It may also be used to produce speciality chemicals such as drug precursors through microbially assisted electrocatalysis. Microbial electrosynthesis can also be used to "power" plants. Plants can then be grown without sunlight.

References

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Comparison to microbial electrolysis cells

Applications

See also

References