Get Propionic Acid essential facts below. View Videos or join the Propionic Acid discussion. Add Propionic Acid to your PopFlock.com topic list for future reference or share this resource on social media.
Propionic acid (, from the Greek words protos, meaning "first", and pion, meaning "fat"; also known as propanoic acid) is a naturally occurring carboxylic acid with chemical formula CH3CH2CO2H. It is a liquid with a pungent and unpleasant smell somewhat resembling body odor. The anion CH3CH2CO2- as well as the salts and esters of propionic acid are known as propionates or propanoates.
Propionic acid was first described in 1844 by Johann Gottlieb, who found it among the degradation products of sugar. Over the next few years, other chemists produced propionic acid by different means, none of them realizing they were producing the same substance. In 1847, French chemist Jean-Baptiste Dumas established all the acids to be the same compound, which he called propionic acid, from the Greek words (pr?tos), meaning first, and ? (pi?n), meaning fat, because it is the smallest H(CH2)nCOOH acid that exhibits the properties of the other fatty acids, such as producing an oily layer when salted out of water and having a soapypotassiumsalt.
Propionic acid has physical properties intermediate between those of the smaller carboxylic acids, formic and acetic acids, and the larger fatty acids. It is miscible with water, but can be removed from water by adding salt. As with acetic and formic acids, it consists of hydrogen bonded pairs of molecules in both the liquid and the vapor.
It is also produced by the aerobic oxidation of propionaldehyde. In the presence of cobalt or manganese salts (manganese propionate is most commonly used), this reaction proceeds rapidly at temperatures as mild as 40-50 °C:
Large amounts of propionic acid were once produced as a byproduct of acetic acid manufacture. At the current time, the world's largest producer of propionic acid is BASF, with approximately 150 kt/a production capacity.
Biotechnological production of propionic acid mainly uses Propionibacterium strains. However, large scale production of propionic acid by Propionibacteria faces challenges such as severe inhibition of end-products during cell growth and the formation of by-products (acetic acid and succinic acid). One approach to improve productivity and yield during fermentation is through the use of cell immobilization techniques, which also promotes easy recovery, reuse of the cell biomass and enhances microorganisms' stress tolerance. In 2018, 3D printing technology was used for the first time to create a matrix for cell immobilization in fermentation. Propionic acid production by Propionibacterium acidipropionici immobilized on 3D-printed nylon beads was chosen as a model study. It was shown that those 3D-printed beads were able to promote high density cell attachment and propionic acid production, which could be adapted to other fermentation bioprocesses. Other cell immobilization matrices have been tested, such as recycled-glass Poraver and fibrous-bed bioreactor.
Alternative methods of production have been trialled, by genetically engineering strains of Escherichia coli to incorporate the necessary pathway, the Wood-Werkman cycle.
Propionic acid inhibits the growth of mold and some bacteria at levels between 0.1 and 1% by weight. As a result, some propionic acid produced is consumed as a preservative for both animal feed and food for human consumption. For animal feed, it is used either directly or as its ammonium salt. The antibiotic monensin is added to cattle feed to favor propionibacteria over acetic acid producers in the rumen; this produces less carbon dioxide and feed conversion is better. This application accounts for about half of the world production of propionic acid. Another major application is as a preservative in baked goods, which use the sodium and calcium salts. As a food additive, it is approved for use in the EU, USA, Australia and New Zealand.
In biogas plants, propionic acid is a common intermediate product, which is formed by fermentation with propionic acid bacteria. Its degradation in anaerobic environments (e.g. biogas plants) requires the activity of complex microbial communities.
In propionic acidemia, a rare inherited genetic disorder, propionate acts as a metabolic toxin in liver cells by accumulating in mitochondria as propionyl-CoA and its derivative, methylcitrate, two tricarboxylic acid cycle inhibitors. Propanoate is metabolized oxidatively by glia, which suggests astrocytic vulnerability in propionic acidemia when intramitochondrial propionyl-CoA may accumulate. Propionic acidemia may alter both neuronal and glial gene expression by affecting histone acetylation. When propionic acid is infused directly into rodents' brains, it produces reversible behavior (e.g., hyperactivity, dystonia, social impairment, perseveration) and brain changes (e.g., innate neuroinflammation, glutathione depletion) that may be used as a means to model autism in rats.
A study in mice suggests that propionate is produced by the bacteria of the genus Bacteroides in the gut, and that it offers some protection against Salmonella there. Another study finds that fatty acid propionate can calm the immune cells that drive up blood pressure, thereby protecting the body from damaging effects of high blood pressure.
The Bacteria species Coprothermobacter platensis produces propionate when fermenting gelatin.
Propionate salts and esters
The propionate , or propanoate, ion is C2H5COO−, the conjugate base of propionic acid. It is the form found in biological systems at physiological pH. A propionic, or propanoic, compound is a carboxylate salt or ester of propionic acid. In these compounds, propionate is often written in shorthand, as CH3CH2CO2 or simply EtCO2.
Propionates should not be confused with propenoates (commonly known as acrylates), the ions/salts/esters of propenoic acid (also known as 2-propenoic acid or acrylic acid).
^ abcdefPropanoic acid in Linstrom, Peter J.; Mallard, William G. (eds.); NIST Chemistry WebBook, NIST Standard Reference Database Number 69, National Institute of Standards and Technology, Gaithersburg (MD), http://webbook.nist.gov (retrieved 2014-06-13)
^Johann Gottlieb (1844) "Ueber die Einwirkung von schmelzendem Kalihydrat auf Rohrzucker, Gummi, Stärkmehl und Mannit" (On the effect of molten potassium hydroxide on raw sugar, rubber, starch powder, and mannitol), Annalen der Chemie und Pharmacie, 52 : 121-130. After combining raw sugar with an excess of potassium hydroxide and distilling the result, Gottlieb obtained a product that he called "Metacetonsäure" (meta-acetone acid) on p. 122: "Das Destillat ist stark sauer und enthält Ameisensäure, Essigsäure und eine neue Säure, welche ich, aus unten anzuführenden Gründen, Metacetonsäure nenne." (The distillate is strongly acidic and contains formic acid, acetic acid, and a new acid, which for reasons to be presented below I call "meta-acetone acid".)
^Dumas, Malaguti, and F. Leblanc (1847) "Sur l'identité des acides métacétonique et butyro-acétique" [On the identity of metacetonic acid and butyro-acetic acid], Comptes rendus, 25 : 781-784. Propionic acid is named on p. 783: "Ces caractères nous ont conduits à désigner cet acide sous le nom d'acide propionique, nom qui rappelle sa place dans la séries des acides gras: il en est le premier." (These characteristics led us to designate this acid by the name of propionic acid, a name that recalls its place in the series of fatty acids: it is the first of them.)
^Liu, Long; Zhu, Yunfeng; Li, Jianghua; Wang, Miao; Lee, Pengsoon; Du, Guocheng; Chen, Jian (2012). "Microbial production of propionic acid from propionibacteria: Current state, challenges and perspectives". Critical Reviews in Biotechnology. 32 (4): 374-381. doi:10.3109/07388551.2011.651428. PMID22299651. S2CID25823025.
^Alonso, Saúl; Rendueles, Manuel; Díaz, Mario (2015). "A novel approach to monitor stress-induced physiological responses in immobilized microorganisms". Applied Microbiology and Biotechnology. 99 (8): 3573-3583. doi:10.1007/s00253-015-6517-1. PMID25776062. S2CID860853.
^Belgrano, Fabricio dos Santos; Diegel, Olaf; Pereira, Nei; Hatti-Kaul, Rajni (2018). "Cell immobilization on 3D-printed matrices: A model study on propionic acid fermentation". Bioresource Technology. 249: 777-782. doi:10.1016/j.biortech.2017.10.087. PMID29136932.
^ abD. F. MacFabe; D. P. Cain; K. Rodriguez-Capote; A. E. Franklin; J. E. Hoffman; F. Boon; A. R. Taylor; M. Kavaliers; K.-P. Ossenkopp (2007). "Neurobiological effects of intraventricular propionic acid in rats: Possible role of short-chain fatty acids on the pathogenesis and characteristics of autism spectrum disorders". Behavioural Brain Research. 176 (1): 149-169. doi:10.1016/j.bbr.2006.07.025. PMID16950524. S2CID3054752.