Acetogenesis

Acetogenesis

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Acetogenesis is a process through which acetate
Acetate
An acetate is a derivative of acetic acid. This term includes salts and esters, as well as the anion found in solution. Most of the approximately 5 billion kilograms of acetic acid produced annually in industry are used in the production of acetates, which usually take the form of polymers. In...

 is produced by anaerobic bacteria from a variety of energy (for example, hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

) and carbon (for example, carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

) sources. The different bacterial species that are capable of acetogenesis are collectively termed acetogen
Acetogen
An acetogen is a microorganism that generates acetate as a product of anaerobic respiration. This process is known as acetogenesis and is different from acetate fermentation, although both occur in the absence of oxygen and produce acetate...

s.

Biochemistry


The precursor to acetic acid is the thioester
Thioester
Thioesters are compounds with the functional group C-S-CO-C. They are the product of esterification between a carboxylic acid and a thiol. Thioesters are widespread in biochemistry, the best-known derivative being acetyl-CoA.-Synthesis:...

 acetyl CoA. The key aspects of the acetogenic pathway are several reactions that include the reduction of carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 to carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...

 and the attachment of the carbon monoxide to a methyl group
Methyl group
Methyl group is a functional group derived from methane, containing one carbon atom bonded to three hydrogen atoms —CH3. The group is often abbreviated Me. Such hydrocarbon groups occur in many organic compounds. The methyl group can be found in three forms: anion, cation and radical. The anion...

. The first process is catalyzed by enzymes called carbon monoxide dehydrogenase. The coupling of the methyl group (provided by methylcobalamin) and the CO is catalyzed by acetyl CoA synthetase.
2 CO2 + 4 H2 → CH3COOH + 2H2O

This pathway is also called the Wood-Ljungdahl pathway.