Propionic acid: Difference between revisions

Propanoic acid
Simplified skeletal formula	Full structural formula
Ball-and-stick model	Space-filling model
Names
	Preferred IUPAC name Propanoic acid
	Other names Propionic acid; Ethanecarboxylic acid
Identifiers
CAS Number	Propionic acid: 79-09-4 ; Propionate: 72-03-7;
3D model (JSmol)	Propionic acid: Interactive image; Propionate: Interactive image;
ChEBI	Propionic acid: CHEBI:30768 ;
ChEMBL	Propionic acid: ChEMBL14021 ;
ChemSpider	Propionic acid: 1005 ; Propionate: 94556;
DrugBank	Propionic acid: DB03766 ;
ECHA InfoCard	100.001.070
EC Number	Propionic acid: 201-176-3;
E number	E280 (preservatives)
IUPHAR/BPS	Propionic acid: 1062;
PubChem CID	Propionic acid: 1032; Propionate: 104745;
RTECS number	Propionic acid: UE5950000;
UNII	Propionic acid: JHU490RVYR ; Propionate: AKW5EM890C;
CompTox Dashboard (EPA)	Propionic acid: DTXSID201058721 DTXSID8025961, DTXSID201058721 ;
	InChI InChI=1S/C3H6O2/c1-2-3(4)5/h2H2,1H3,(H,4,5) Key: XBDQKXXYIPTUBI-UHFFFAOYSA-N ;
	SMILES Propionic acid: CCC(=O)O; Propionate: CCC(=O)[O-];
Properties
Chemical formula	C3H6O2
Molar mass	74.079 g·mol−1
Appearance	Colorless, oily liquid
Odor	Pungent, rancid, unpleasant
Density	0.98797 g/cm3
Melting point	−20.5 °C (−4.9 °F; 252.7 K)
Boiling point	141.15 °C (286.07 °F; 414.30 K)
Sublimation; conditions	Sublimes at −48 °C; ΔsublHo = 74 kJ/mol
Solubility in water	8.19 g/g (−28.3 °C); 34.97 g/g (−23.9 °C); Miscible (≥ −19.3 °C)
Solubility	Miscible in EtOH, ether, CHCl3
log P	0.33
Vapor pressure	0.32 kPa (20 °C); 0.47 kPa (25 °C); 9.62 kPa (100 °C)
Henry's law; constant (kH)	4.45·10−4 L·atm/mol
Acidity (pKa)	4.88
Magnetic susceptibility (χ)	-43.50·10−6 cm3/mol
Refractive index (nD)	1.3843
Viscosity	1.175 cP (15 °C); 1.02 cP (25 °C); 0.668 cP (60 °C); 0.495 cP (90 °C)
Structure
Crystal structure	Monoclinic (−95 °C)
Space group	P21/c
Lattice constant	a = 4.04 Å, b = 9.06 Å, c = 11 Å α = 90°, β = 91.25°, γ = 90°
Dipole moment	0.63 D (22 °C)
Thermochemistry
Heat capacity (C)	152.8 J/mol·K
Std molar; entropy (S⦵298)	191 J/mol·K
Std enthalpy of; formation (ΔfH⦵298)	−510.8 kJ/mol
Std enthalpy of; combustion (ΔcH⦵298)	1527.3 kJ/mol
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	Corrosive
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H314
Precautionary statements	P280, P305+P351+P338, P310
NFPA 704 (fire diamond)	3 2 0
Flash point	54 °C (129 °F; 327 K)
Autoignition; temperature	512 °C (954 °F; 785 K)
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	1370 mg/kg (mouse, oral)
	NIOSH (US health exposure limits):
PEL (Permissible)	none
REL (Recommended)	TWA 10 ppm (30 mg/m3) ST 15 ppm (45 mg/m3)
IDLH (Immediate danger)	N.D.
Related compounds
Other anions	Propanoate
Related Carboxylic acids	Acetic acid; Lactic acid; 3-hydroxypropionic acid; Tartronic acid; Acrylic acid; Butyric acid
Related compounds	1-Propanol; Propionaldehyde; Sodium propionate; Propionic anhydride
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

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Propionic acid (/proʊpiˈɒnɪk/, 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.

History

Propionic acid was first described in 1844 by Johann Gottlieb, who found it among the degradation products of sugar.^[10] 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 πρῶτος (prōtos), meaning first, and πίων (piōn), 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 soapy potassium salt.^[11]

Properties

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.

Propionic acid displays the general properties of carboxylic acids: it can form amide, ester, anhydride, and chloride derivatives. It undergoes the Hell–Volhard–Zelinsky reaction that involves α-halogenation of a carboxylic acid with bromine, catalysed by phosphorus tribromide, in this case to form 2-bromopropanoic acid, CH₃CHBrCOOH.^[12] This product has been used to prepare a racemic mixture of alanine by ammonolysis.^[13]^[14]

Manufacture

Chemical

In industry, propionic acid is mainly produced by the hydrocarboxylation of ethylene using nickel carbonyl as the catalyst:^[15]

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

Biotechnological production of propionic acid mainly uses Propionibacterium strains.^[16] 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).^[17] 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.^[18] 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.^[19] Other cell immobilization matrices have been tested, such as recycled-glass Poraver and fibrous-bed bioreactor.^[20]^[21]

Alternative methods of production have been trialled, by genetically engineering strains of Escherichia coli to incorporate the necessary pathway, the Wood-Werkman cycle.^[22]

Industrial uses

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.^[15] As a food additive, it is approved for use in the EU,^[23] USA,^[24] Australia and New Zealand.^[25]

Propionic acid is also useful as an intermediate in the production of other chemicals, especially polymers. Cellulose-acetate-propionate is a useful thermoplastic. Vinyl propionate is also used. In more specialized applications, it is also used to make pesticides and pharmaceuticals. The esters of propionic acid have fruit-like odors and are sometimes used as solvents or artificial flavorings.^[15]

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.^[26]

Biology

Propionic acid is produced biologically as its coenzyme A ester, propionyl-CoA, from the metabolic breakdown of fatty acids containing odd numbers of carbon atoms, and also from the breakdown of some amino acids. Bacteria of the genus Propionibacterium produce propionic acid as the end-product of their anaerobic metabolism. This class of bacteria is commonly found in the stomachs of ruminants and the sweat glands of humans, and their activity is partially responsible for the odor of Emmental cheese, American "Swiss cheese" and sweat.

The metabolism of propionic acid begins with its conversion to propionyl coenzyme A, the usual first step in the metabolism of carboxylic acids. Since propionic acid has three carbons, propionyl-CoA cannot directly enter either beta oxidation or the citric acid cycles. In most vertebrates, propionyl-CoA is carboxylated to D-methylmalonyl-CoA, which is isomerised to L-methylmalonyl-CoA. A vitamin B₁₂-dependent enzyme catalyzes rearrangement of L-methylmalonyl-CoA to succinyl-CoA, which is an intermediate of the citric acid cycle and can be readily incorporated there.

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.^[27]^[28] 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.^[27]

It also, being a three-carbon molecule, feeds into hepatic gluconeogenesis (that is, the creation of glucose molecules from simpler molecules in the liver).^[29]

Human occurrence

The human skin is host of several species of Propionibacteria. The most notable one is the Cutibacterium acnes (formerly known as Propionibacterium acnes), which lives mainly in the sebaceous glands of the skin and is one of the principal causes of acne.^[30] Propionate is observed to be among the most common short-chain fatty acids produced in the large intestine of humans by gut microbiota in response to indigestible carbohydrates (dietary fiber) in the diet.^[31]^[32] The role of the gut microbiota and their metabolites, including propionate, in mediating brain function has been reviewed.^[33]

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.^[34] 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.^[35]

Bacteriology

The Bacteria species Coprothermobacter platensis produces propionate when fermenting gelatin.^[36]

Propionate salts and esters

The propionate /ˈproʊpiəneɪt/, 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 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).

Examples

Salts

Sodium propionate NaC₂H₅CO₂
Potassium propionate KC₂H₅CO₂
Calcium propionate Ca(C₂H₅CO₂)₂
Zirconium propionate Zr(C₂H₅CO₂)₄

Esters

Methyl propionate (C₂H₅(CO)OCH₃)
Ethyl propionate (C₂H₅(CO)OC₂H₅)
Propyl propionate (C₂H₅(CO)OC₃H₇)
Pentyl propionate (C₂H₅(CO)OC₅H₁₁)
Fluticasone propionate C₂₅H₃₁F₃O₅S

References

^ ^a ^b ^c ^d ^e NIOSH Pocket Guide to Chemical Hazards. "#0529". National Institute for Occupational Safety and Health (NIOSH).
^ ^a ^b ^c ^d ^e Lagowski, J.J., ed. (2012). The Chemistry of Nonaqueous Solvents. Vol. III. Elsevier. p. 362. ISBN 978-0323151030.
^ ^a ^b Lide, David R., ed. (2009). CRC Handbook of Chemistry and Physics (90th ed.). Boca Raton, Florida: CRC Press. ISBN 978-1-4200-9084-0.
^ ^a ^b ^c ^d ^e ^f Propanoic 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) (retrieved 2014-06-13)
^ Seidell, Atherton; Linke, William F. (1919). Solubilities of Inorganic and Organic Compounds (2nd ed.). D. Van Nostrand Company. p. 569.
^ ^a ^b ^c "chemister.ru (archived copy)". Archived from the original on 2016-10-09. Retrieved 2014-06-13.
^ ^a ^b ^c ^d ^e CID 1032 from PubChem
^ ^a ^b ^c ^d ^e Sigma-Aldrich Co., Propionic acid. Retrieved on 2014-06-13.
^ ^a ^b ^c Strieter, F. J.; Templeton, D. H.; Scheuerman, R. F.; Sass, R. L. (1962). "The crystal structure of propionic acid". Acta Crystallographica. 15 (12): 1233–1239. doi:10.1107/S0365110X62003278.
^ 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.)
^ Marvel, C. S.; du Vigneaud, V. (1931). "α-Bromoisovaleric acid". Organic Syntheses. 11: 20. doi:10.15227/orgsyn.011.0020; Collected Volumes, vol. 2, p. 93.
^ Tobie, Walter C.; Ayres, Gilbert B. (1937). "Synthesis of d,l-Alanine in Improved Yield from α-Bromopropionic Acid and Aqueous Ammonia". Journal of the American Chemical Society. 59 (5): 950. doi:10.1021/ja01284a510.
^ Tobie, Walter C.; Ayres, Gilbert B. (1941). "dl-Alanine". Organic Syntheses. doi:10.15227/orgsyn.009.0004; Collected Volumes, vol. 1, p. 21.
^ ^a ^b ^c Ulf‐Rainer Samel, Walter Kohler, Armin Otto Gamer, Ullrich Keuser, Shang‐Tian Yang, Ying Jin, Meng Lin, Zhongqiang Wang, Joaquim Henrique Teles (2018). "Propionic Acid and Derivatives". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a22_223.pub4. ISBN 978-3527306732.{{cite encyclopedia}}: CS1 maint: multiple names: authors list (link)
^ Piwowarek, Kamil; Lipińska, Edyta; Hać-Szymańczuk, Elżbieta; Kieliszek, Marek; Ścibisz, Iwona (2018). "Propionibacterium SPP.—source of propionic acid, vitamin B12, and other metabolites important for the industry". Applied Microbiology and Biotechnology. 102 (2): 515–538. doi:10.1007/s00253-017-8616-7. PMID 29167919. S2CID 23599974.
^ 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. PMID 22299651.
^ 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. PMID 25776062.
^ 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. PMID 29136932.
^ Dishisha, Tarek; Alvarez, Maria Teresa; Hatti-Kaul, Rajni (2012). "Batch- and continuous propionic acid production from glycerol using free and immobilized cells of Propionibacterium acidipropionici" (PDF). Bioresource Technology. 118: 553–562. doi:10.1016/j.biortech.2012.05.079. PMID 22728152.
^ Suwannakham, Supaporn; Yang, Shang-Tian (2005). "Enhanced propionic acid fermentation by Propionibacterium acidipropionici mutant obtained by adaptation in a fibrous-bed bioreactor". Biotechnology and Bioengineering. 91 (3): 325–337. doi:10.1002/bit.20473. PMID 15977254.
^ Gonzalez‐Garcia, Ricardo A.; McCubbin, Timothy; Turner, Mark S.; Nielsen, Lars K.; Marcellin, Esteban (2020). "Engineering Escherichia coli for propionic acid production through the Wood–Werkman cycle". Biotechnology and Bioengineering. 117 (1): 167–183. doi:10.1002/bit.27182. PMID 31556457. S2CID 203438727.
^ "Current EU approved additives and their E Numbers". UK Food Standards Agency. Retrieved 2011-10-27.
^ "Listing of Food Additives Status Part II". US Food and Drug Administration. Retrieved 2011-10-27.
^ "Standard 1.2.4 – Labelling of ingredients". Australia New Zealand Food Standards Code. Comlaw.au. Retrieved 2011-10-27.
^ Ahlert, Stephan; Zimmermann, Rita; Ebling, Johannes; König, Helmut (2016). "Analysis of propionate-degrading consortia from agricultural biogas plants". MicrobiologyOpen. 5 (6): 1027–1037. doi:10.1002/mbo3.386. PMC 5221444. PMID 27364538.
^ ^a ^b D. 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. PMID 16950524.
^ N. H. T. Nguyen; C. Morland; S. Villa Gonzalez; F. Rise; J. Storm-Mathisen; V. Gundersen; B. Hassel (2007). "Propionate increases neuronal histone acetylation, but is metabolized oxidatively by glia. Relevance for propionic acidemia". Journal of Neurochemistry. 101 (3): 806–814. doi:10.1111/j.1471-4159.2006.04397.x. PMID 17286595.
^ Aschenbach, JR; Kristensen, NB; Donkin, SS; Hammon, HM; Penner, GB (December 2010). "Gluconeogenesis in dairy cows: the secret of making sweet milk from sour dough". IUBMB Life. 62 (12): 869–77. doi:10.1002/iub.400. PMID 21171012.
^ Bojar, Richard A.; Holland, Keith T. (2004). "Acne and propionibacterium acnes". Clinics in Dermatology. 22 (5): 375–379. doi:10.1016/j.clindermatol.2004.03.005.
^ Cani, Patrice D.; Knauf, Claude (27 May 2016). "How gut microbes talk to organs: The role of endocrine and nervous routes". Molecular Metabolism. 5 (9): 743–752. doi:10.1016/j.molmet.2016.05.011. PMC 5004142. PMID 27617197.
^ den Besten, G; van Eunen, K; Groen, AK; Venema, K; Reijngoud, DJ; Bakker, BM (September 2013). "The role of short-chain fatty acids in the interplay between diet, gut microbiota, and host energy metabolism". Journal of Lipid Research. 54 (9): 2325–40. doi:10.1194/jlr.R036012. PMC 3735932. PMID 23821742.{{cite journal}}: CS1 maint: unflagged free DOI (link)
^ "From gut dysbiosis to altered brain function and mental illness: mechanisms and pathways". doi:10.1038/mp.2016.50. {{cite journal}}: Cite journal requires |journal= (help)
^ Jacobson, Amanda; Lam, Lilian; Rajendram, Manohary; Tamburini, Fiona; Honeycutt, Jared; Pham, Trung; Van Treuren, Will; Pruss, Kali; Stabler, Stephen Russell; Lugo, Kyler; Bouley, Donna M.; Vilches-Moure, Jose G.; Smith, Mark; Sonnenburg, Justin L.; Bhatt, Ami S.; Huang, Kerwyn Casey; Monack, Denise (2018). "A Gut Commensal-Produced Metabolite Mediates Colonization Resistance to Salmonella Infection". Cell Host & Microbe. 24 (2): 296–307.e7. doi:10.1016/j.chom.2018.07.002. PMID 30057174.
^ Bartolomaeus, Hendrik; Balogh, András; Yakoub, Mina; Homann, Susanne; Markó, Lajos; Höges, Sascha; Tsvetkov, Dmitry; Krannich, Alexander; Wundersitz, Sebastian; Avery, Ellen G.; Haase, Nadine; Kräker, Kristin; Hering, Lydia; Maase, Martina; Kusche-Vihrog, Kristina; Grandoch, Maria; Fielitz, Jens; Kempa, Stefan; Gollasch, Maik; Zhumadilov, Zhaxybay; Kozhakhmetov, Samat; Kushugulova, Almagul; Eckardt, Kai-Uwe; Dechend, Ralf; Rump, Lars Christian; Forslund, Sofia K.; Müller, Dominik N.; Stegbauer, Johannes; Wilck, Nicola (2019). "Short-Chain Fatty Acid Propionate Protects from Hypertensive Cardiovascular Damage". Circulation. 139 (11): 1407–1421. doi:10.1161/CIRCULATIONAHA.118.036652. PMC 6416008. PMID 30586752.
^ Etchebehere, C.; Pavan, M. E.; Zorzópulos, J.; Soubes, M.; Muxí, L. (October 1998). "Coprothermobacter platensis sp. nov., a new anaerobic proteolytic thermophilic bacterium isolated from an anaerobic mesophilic sludge". International Journal of Systematic Bacteriology. 48 Pt 4 (4): 1297–1304. doi:10.1099/00207713-48-4-1297. ISSN 0020-7713. PMID 9828430.

External links

[PGCH-1] NIOSH Pocket Guide to Chemical Hazards. "#0529". National Institute for Occupational Safety and Health (NIOSH).

[cons3-2] Lagowski, J.J., ed. (2012). The Chemistry of Nonaqueous Solvents. Vol. III. Elsevier. p. 362. ISBN 978-0323151030.

[crc-3] Lide, David R., ed. (2009). CRC Handbook of Chemistry and Physics (90th ed.). Boca Raton, Florida: CRC Press. ISBN 978-1-4200-9084-0.

[nist-4] ^ ^a ^b ^c ^d ^e ^f Propanoic 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) (retrieved 2014-06-13)

[sioc-5] Seidell, Atherton; Linke, William F. (1919). Solubilities of Inorganic and Organic Compounds (2nd ed.). D. Van Nostrand Company. p. 569.

[chemister-6] "chemister.ru (archived copy)". Archived from the original on 2016-10-09. Retrieved 2014-06-13.

[pubchem-7] CID 1032 from PubChem

[sigma-8] Sigma-Aldrich Co., Propionic acid. Retrieved on 2014-06-13.

[csba-9] Strieter, F. J.; Templeton, D. H.; Scheuerman, R. F.; Sass, R. L. (1962). "The crystal structure of propionic acid". Acta Crystallographica. 15 (12): 1233–1239. doi:10.1107/S0365110X62003278.

[10] 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".)

[11] 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.)

[12] Marvel, C. S.; du Vigneaud, V. (1931). "α-Bromoisovaleric acid". Organic Syntheses. 11: 20. doi:10.15227/orgsyn.011.0020; Collected Volumes, vol. 2, p. 93.

[13] Tobie, Walter C.; Ayres, Gilbert B. (1937). "Synthesis of d,l-Alanine in Improved Yield from α-Bromopropionic Acid and Aqueous Ammonia". Journal of the American Chemical Society. 59 (5): 950. doi:10.1021/ja01284a510.

[14] Tobie, Walter C.; Ayres, Gilbert B. (1941). "dl-Alanine". Organic Syntheses. doi:10.15227/orgsyn.009.0004; Collected Volumes, vol. 1, p. 21.

[Ullmann-15] Ulf‐Rainer Samel, Walter Kohler, Armin Otto Gamer, Ullrich Keuser, Shang‐Tian Yang, Ying Jin, Meng Lin, Zhongqiang Wang, Joaquim Henrique Teles (2018). "Propionic Acid and Derivatives". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a22_223.pub4. ISBN 978-3527306732.{{cite encyclopedia}}: CS1 maint: multiple names: authors list (link)

[16] Piwowarek, Kamil; Lipińska, Edyta; Hać-Szymańczuk, Elżbieta; Kieliszek, Marek; Ścibisz, Iwona (2018). "Propionibacterium SPP.—source of propionic acid, vitamin B12, and other metabolites important for the industry". Applied Microbiology and Biotechnology. 102 (2): 515–538. doi:10.1007/s00253-017-8616-7. PMID 29167919. S2CID 23599974.

[17] 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. PMID 22299651.

[18] 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. PMID 25776062.

[19] 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. PMID 29136932.

[20] Dishisha, Tarek; Alvarez, Maria Teresa; Hatti-Kaul, Rajni (2012). "Batch- and continuous propionic acid production from glycerol using free and immobilized cells of Propionibacterium acidipropionici" (PDF). Bioresource Technology. 118: 553–562. doi:10.1016/j.biortech.2012.05.079. PMID 22728152.

[21] Suwannakham, Supaporn; Yang, Shang-Tian (2005). "Enhanced propionic acid fermentation by Propionibacterium acidipropionici mutant obtained by adaptation in a fibrous-bed bioreactor". Biotechnology and Bioengineering. 91 (3): 325–337. doi:10.1002/bit.20473. PMID 15977254.

[22] Gonzalez‐Garcia, Ricardo A.; McCubbin, Timothy; Turner, Mark S.; Nielsen, Lars K.; Marcellin, Esteban (2020). "Engineering Escherichia coli for propionic acid production through the Wood–Werkman cycle". Biotechnology and Bioengineering. 117 (1): 167–183. doi:10.1002/bit.27182. PMID 31556457. S2CID 203438727.

[23] "Current EU approved additives and their E Numbers". UK Food Standards Agency. Retrieved 2011-10-27.

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[25] "Standard 1.2.4 – Labelling of ingredients". Australia New Zealand Food Standards Code. Comlaw.au. Retrieved 2011-10-27.

[Ahlert-26] Ahlert, Stephan; Zimmermann, Rita; Ebling, Johannes; König, Helmut (2016). "Analysis of propionate-degrading consortia from agricultural biogas plants". MicrobiologyOpen. 5 (6): 1027–1037. doi:10.1002/mbo3.386. PMC 5221444. PMID 27364538.

[macfabe-27] D. 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. PMID 16950524.

[28] N. H. T. Nguyen; C. Morland; S. Villa Gonzalez; F. Rise; J. Storm-Mathisen; V. Gundersen; B. Hassel (2007). "Propionate increases neuronal histone acetylation, but is metabolized oxidatively by glia. Relevance for propionic acidemia". Journal of Neurochemistry. 101 (3): 806–814. doi:10.1111/j.1471-4159.2006.04397.x. PMID 17286595.

[29] Aschenbach, JR; Kristensen, NB; Donkin, SS; Hammon, HM; Penner, GB (December 2010). "Gluconeogenesis in dairy cows: the secret of making sweet milk from sour dough". IUBMB Life. 62 (12): 869–77. doi:10.1002/iub.400. PMID 21171012.

[30] Bojar, Richard A.; Holland, Keith T. (2004). "Acne and propionibacterium acnes". Clinics in Dermatology. 22 (5): 375–379. doi:10.1016/j.clindermatol.2004.03.005.

[31] Cani, Patrice D.; Knauf, Claude (27 May 2016). "How gut microbes talk to organs: The role of endocrine and nervous routes". Molecular Metabolism. 5 (9): 743–752. doi:10.1016/j.molmet.2016.05.011. PMC 5004142. PMID 27617197.

[metab-32] Besten, G; van Eunen, K; Groen, AK; Venema, K; Reijngoud, DJ; Bakker, BM (September 2013). "The role of short-chain fatty acids in the interplay between diet, gut microbiota, and host energy metabolism". Journal of Lipid Research. 54 (9): 2325–40. doi:10.1194/jlr.R036012. PMC 3735932. PMID 23821742.{{cite journal}}: CS1 maint: unflagged free DOI (link)

[33] "From gut dysbiosis to altered brain function and mental illness: mechanisms and pathways". doi:10.1038/mp.2016.50. {{cite journal}}: Cite journal requires |journal= (help)

[34] Jacobson, Amanda; Lam, Lilian; Rajendram, Manohary; Tamburini, Fiona; Honeycutt, Jared; Pham, Trung; Van Treuren, Will; Pruss, Kali; Stabler, Stephen Russell; Lugo, Kyler; Bouley, Donna M.; Vilches-Moure, Jose G.; Smith, Mark; Sonnenburg, Justin L.; Bhatt, Ami S.; Huang, Kerwyn Casey; Monack, Denise (2018). "A Gut Commensal-Produced Metabolite Mediates Colonization Resistance to Salmonella Infection". Cell Host & Microbe. 24 (2): 296–307.e7. doi:10.1016/j.chom.2018.07.002. PMID 30057174.

[35] Bartolomaeus, Hendrik; Balogh, András; Yakoub, Mina; Homann, Susanne; Markó, Lajos; Höges, Sascha; Tsvetkov, Dmitry; Krannich, Alexander; Wundersitz, Sebastian; Avery, Ellen G.; Haase, Nadine; Kräker, Kristin; Hering, Lydia; Maase, Martina; Kusche-Vihrog, Kristina; Grandoch, Maria; Fielitz, Jens; Kempa, Stefan; Gollasch, Maik; Zhumadilov, Zhaxybay; Kozhakhmetov, Samat; Kushugulova, Almagul; Eckardt, Kai-Uwe; Dechend, Ralf; Rump, Lars Christian; Forslund, Sofia K.; Müller, Dominik N.; Stegbauer, Johannes; Wilck, Nicola (2019). "Short-Chain Fatty Acid Propionate Protects from Hypertensive Cardiovascular Damage". Circulation. 139 (11): 1407–1421. doi:10.1161/CIRCULATIONAHA.118.036652. PMC 6416008. PMID 30586752.

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@@ Line 1: / Line 1: @@
 {{short description|Carboxylic acid with chemical formula CH3CH2CO2H}}
 {{Chembox
-| Watchedfields = changed
-| verifiedrevid = 476992570
 | Name = Propanoic acid
 | ImageFileL1 = Propionic_acid_chemical_structure.svg
@@ Line 21: / Line 19: @@
 | OtherNames = Propionic acid<br />Ethanecarboxylic acid
 |Section1={{Chembox Identifiers
+| index_label    = Propionic acid
+| index1_label   = Propionate
 | IUPHAR_ligand = 1062
 | DrugBank_Ref = {{drugbankcite|correct|drugbank}}
@@ Line 37: / Line 37: @@
 | ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
 | ChemSpiderID = 1005
-| SMILES2 = CCC(O)=O
 | StdInChI_Ref = {{stdinchicite|correct|chemspider}}
 | StdInChI = 1S/C3H6O2/c1-2-3(4)5/h2H2,1H3,(H,4,5)
@@ Line 43: / Line 42: @@
 | StdInChIKey = XBDQKXXYIPTUBI-UHFFFAOYSA-N
 | RTECS = UE5950000
+| CASNo1 = 72-03-7
+| CASNo_Ref1 = {{cascite|correct|CAS}}
+| UNII1 = AKW5EM890C
+| UNII_Ref1 = {{fdacite|correct|FDA}}
+| SMILES1 = CCC(=O)[O-]
+| PubChem1 = 104745
+| ChemSpiderID1 = 94556
  }}
 |Section2={{Chembox Properties
@@ Line 49: / Line 55: @@
 | Odor = Pungent, rancid, unpleasant<ref name=PGCH/>
 | Density = 0.98797 g/cm<sup>3</sup><ref name=cons3 />
-| Solubility = 8.19 g/g (−28.3 °C)<br /> 34.97 g/g (−23.9 °C)<br /> Miscible (≥ −19.3 °C)<ref name=sioc>{{cite book|last1 = Seidell|first1 = Atherton|last2 = Linke|first2 = William F.|year = 1919|title = Solubilities of Inorganic and Organic Compounds|url = https://archive.org/details/solubilitiesino01seidgoog|publisher = D. Van Nostrand Company|edition = 2nd|page = 569}}</ref>
+| Solubility = 8.19 g/g (−28.3 °C)<br /> 34.97 g/g (−23.9 °C)<br /> Miscible (≥ −19.3 °C)<ref name=sioc>{{cite book|last = Seidell|first = Atherton|last2 = Linke|first2 = William F.|year = 1919|title = Solubilities of Inorganic and Organic Compounds|url = https://archive.org/details/solubilitiesino01seidgoog|publisher = D. Van Nostrand Company|edition = 2nd|page = 569}}</ref>
-| SolubleOther = Miscible in [[ethanol|EtOH]], [[diethyl ether|ether]], [[chloroform|CHCl<sub>3</sub>]]<ref name=chemister>{{Cite web |url=http://chemister.ru/Database/properties-en.php?dbid=1&id=1485 |title=Archived copy |access-date=2014-06-13 |archive-url=https://web.archive.org/web/20161009114215/http://chemister.ru/Database/properties-en.php?dbid=1&id=1485 |archive-date=2016-10-09 |url-status=dead }}</ref>
+| SolubleOther = Miscible in [[ethanol|EtOH]], [[diethyl ether|ether]], [[chloroform|CHCl<sub>3</sub>]]<ref name=chemister>{{Cite web |url=http://chemister.ru/Database/properties-en.php?dbid=1&id=1485 |title=chemister.ru (archived copy) |access-date=2014-06-13 |archive-url=https://web.archive.org/web/20161009114215/http://chemister.ru/Database/properties-en.php?dbid=1&id=1485 |archive-date=2016-10-09 |url-status=dead }}</ref>
 | MeltingPtC = −20.5
 | MeltingPt_notes = <ref name=crc>{{CRC90}}</ref>
@@ Line 108: / Line 114: @@
 ==History==
-Propionic acid was first described in 1844 by [[Johann Gottlieb]], who found it among the degradation products of [[sugar]].<ref>Johann Gottlieb (1844) [https://babel.hathitrust.org/cgi/pt?id=uva.x002457921;view=1up;seq=581 "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".)</ref> Over the next few years, other chemists produced propionic acid in various other ways, 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 language|Greek]] words πρῶτος (prōtos), meaning ''first'', and πίων (piōn), meaning ''fat'', because it is the smallest H(CH<sub>2</sub>)<sub>''n''</sub>COOH acid that exhibits the properties of the other [[fatty acid]]s, such as producing an oily layer when salted out of water and having a [[soap]]y [[potassium]] [[Potassium propionate|salt]].<ref>Dumas, Malaguti, and F. Leblanc (1847) [http://gallica.bnf.fr/ark:/12148/bpt6k2982c/f785.item.r=.zoom "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.)</ref>
+Propionic acid was first described in 1844 by [[Johann Gottlieb]], who found it among the degradation products of [[sugar]].<ref>Johann Gottlieb (1844) [https://babel.hathitrust.org/cgi/pt?id=uva.x002457921;view=1up;seq=581 "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".)</ref> 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 language|Greek]] words πρῶτος (prōtos), meaning ''first'', and πίων (piōn), meaning ''fat'', because it is the smallest H(CH<sub>2</sub>)<sub>''n''</sub>COOH acid that exhibits the properties of the other [[fatty acid]]s, such as producing an oily layer when salted out of water and having a [[soap]]y [[potassium]] [[Potassium propionate|salt]].<ref>Dumas, Malaguti, and F. Leblanc (1847) [http://gallica.bnf.fr/ark:/12148/bpt6k2982c/f785.item.r=.zoom "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.)</ref>
 ==Properties==
-Propionic acid has physical properties intermediate between those of the smaller carboxylic acids, [[formic acid|formic]] and [[Acetic acid|acetic]] acids, and the larger [[fatty acid]]s.  It is miscible with water, but can be removed from water by adding salt.  As with acetic and formic acids, it consists of [[hydrogen bond]]ed pairs of molecules as both the liquid and the vapor.
+Propionic acid has physical properties intermediate between those of the smaller carboxylic acids, [[formic acid|formic]] and [[Acetic acid|acetic]] acids, and the larger [[fatty acid]]s.  It is miscible with water, but can be removed from water by adding salt.  As with acetic and formic acids, it consists of [[hydrogen bond]]ed pairs of molecules in both the liquid and the vapor.
-Propionic acid displays the general properties of carboxylic acids: it can form [[amide]], [[ester]], [[acid anhydride|anhydride]], and [[acyl chloride|chloride]] derivatives.  It undergoes the [[Hell–Volhard–Zelinsky halogenation|Hell–Volhard–Zelinsky reaction]] that involves α-[[halogenation]] of a carboxylic acid with [[bromine]], [[catalyst|catalysed]] by [[phosphorus tribromide]], in this case to form [[2-bromopropanoic acid]], CH<sub>3</sub>CHBrCOOH.<ref>{{OrgSynth | first1 = C. S. | last1 = Marvel | first2 = V. | last2 = du Vigneaud | title = α-Bromoisovaleric acid | volume = 11 | pages = 20 | collvol = 2 | collvolpages = 93 | year = 1931 | prep = cv2p0093 | doi = 10.15227/orgsyn.011.0020 }}</ref>  This product has been used to prepare a [[racemic mixture]] of [[alanine]] by [[Solvolysis#ammonolysis|ammonolysis]].<ref>{{cite journal|title = Synthesis of ''d'',''l''-Alanine in Improved Yield from α-Bromopropionic Acid and Aqueous Ammonia|first1 = Walter C.|last1 = Tobie|first2 = Gilbert B.|last2 = Ayres|journal = [[Journal of the American Chemical Society]]|year = 1937|volume = 59|issue = 5|page = 950|doi = 10.1021/ja01284a510|doi-access = free}}</ref><ref>{{OrgSynth | first1 = Walter C. | last1 = Tobie | first2 = Gilbert B. | last2 = Ayres | title = ''dl''-Alanine | prep = cv1p0021 | year = 1941 | collvol = 1 | collvolpages = 21 | doi = 10.15227/orgsyn.009.0004 }}</ref>
+Propionic acid displays the general properties of carboxylic acids: it can form [[amide]], [[ester]], [[acid anhydride|anhydride]], and [[acyl chloride|chloride]] derivatives.  It undergoes the [[Hell–Volhard–Zelinsky halogenation|Hell–Volhard–Zelinsky reaction]] that involves α-[[halogenation]] of a carboxylic acid with [[bromine]], [[catalyst|catalysed]] by [[phosphorus tribromide]], in this case to form [[2-bromopropanoic acid]], CH<sub>3</sub>CHBrCOOH.<ref>{{OrgSynth | first1 = C. S. | last1 = Marvel | first2 = V. | last2 = du Vigneaud | title = α-Bromoisovaleric acid | volume = 11 | pages = 20 | collvol = 2 | collvolpages = 93 | year = 1931 | prep = cv2p0093 | doi = 10.15227/orgsyn.011.0020 }}</ref>  This product has been used to prepare a [[racemic mixture]] of [[alanine]] by [[Solvolysis#ammonolysis|ammonolysis]].<ref>{{cite journal|title = Synthesis of ''d'',''l''-Alanine in Improved Yield from α-Bromopropionic Acid and Aqueous Ammonia|first1 = Walter C.|last1 = Tobie|first2 = Gilbert B.|last2 = Ayres|journal = [[Journal of the American Chemical Society]]|year = 1937|volume = 59|issue = 5|page = 950|doi = 10.1021/ja01284a510|doi-access = free}}</ref><ref>{{OrgSynth | first1 = Walter C. | last1 = Tobie | first2 = Gilbert B. | last2 = Ayres | title = ''dl''-Alanine | prep = cv1p0021 | year = 1941 | collvol = 1 | collvolpages = 21 | doi = 10.15227/orgsyn.009.0004 |doi-access = free}}</ref>
 <!--- Note: This Org Synth manuscript is in two parts; the Kendall and McKenzie part was first published in 1929 (vol 9, p. 4) and deals with a Strecker synthesis of alanine.  The second part by Tobie and Ayres was first published in JACS in 1937 and appended to the Kendall and McKenzie Org Synth report in collvol 1 in 1941.  It is the second part that relates to preparing alanine from 2-bromopropanoic acid.  Please be careful if checking / changing these reference, which do share most citation details.  --->
 ::[[File:Preparation of alanine from propionic acid.png|600px]]
-==Production==
+==Manufacture==
+===Chemical===
 In industry, propionic acid is mainly produced by the [[Carbonylation#Reppe chemistry|hydrocarboxylation]] of [[ethylene]] using [[nickel carbonyl]] as the catalyst:<ref name=Ullmann>{{ Ullmann | year=2018|author = Ulf‐Rainer Samel, Walter Kohler, Armin Otto Gamer, Ullrich Keuser, Shang‐Tian Yang, Ying Jin, Meng Lin, Zhongqiang Wang, Joaquim Henrique Teles | title = Propionic Acid and Derivatives| doi = 10.1002/14356007.a22_223.pub4 }}</ref>
@@ Line 128: / Line 135: @@
 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===
+Biotechnological production of propionic acid mainly uses ''[[Propionibacterium]]'' strains.<ref>{{cite journal |doi=10.1007/s00253-017-8616-7 |title=Propionibacterium SPP.—source of propionic acid, vitamin B12, and other metabolites important for the industry |year=2018 |last1=Piwowarek |first1=Kamil |last2=Lipińska |first2=Edyta |last3=Hać-Szymańczuk |first3=Elżbieta |last4=Kieliszek |first4=Marek |last5=Ścibisz |first5=Iwona |journal=Applied Microbiology and Biotechnology |volume=102 |issue=2 |pages=515–538 |pmid=29167919 |s2cid=23599974 }}</ref> 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).<ref>{{Cite journal|doi = 10.3109/07388551.2011.651428|pmid = 22299651|title = Microbial production of propionic acid from propionibacteria: Current state, challenges and perspectives|journal = Critical Reviews in Biotechnology|volume = 32|issue = 4|pages = 374–381|year = 2012|last1 = Liu|first1 = Long|last2 = Zhu|first2 = Yunfeng|last3 = Li|first3 = Jianghua|last4 = Wang|first4 = Miao|last5 = Lee|first5 = Pengsoon|last6 = Du|first6 = Guocheng|last7 = Chen|first7 = Jian}}</ref> 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.<ref>{{cite journal | doi = 10.1007/s00253-015-6517-1| pmid = 25776062| title = A novel approach to monitor stress-induced physiological responses in immobilized microorganisms| journal = Applied Microbiology and Biotechnology| volume = 99| issue = 8| pages = 3573–3583| year = 2015| last1 = Alonso| first1 = Saúl| last2 = Rendueles| first2 = Manuel| last3 = Díaz| first3 = Mario}}</ref> 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.<ref>{{cite journal | doi = 10.1016/j.biortech.2017.10.087| pmid = 29136932| title = Cell immobilization on 3D-printed matrices: A model study on propionic acid fermentation| journal = Bioresource Technology| volume = 249| pages = 777–782| year = 2018| last1 = Belgrano| first1 = Fabricio dos Santos| last2 = Diegel| first2 = Olaf| last3 = Pereira| first3 = Nei| last4 = Hatti-Kaul| first4 = Rajni}}</ref> Other cell immobilization matrices have been tested, such as recycled-glass Poraver and fibrous-bed bioreactor.<ref>{{cite journal | doi = 10.1016/j.biortech.2012.05.079| pmid = 22728152| title = Batch- and continuous propionic acid production from glycerol using free and immobilized cells of Propionibacterium acidipropionici| journal = Bioresource Technology| volume = 118| pages = 553–562| year = 2012| last1 = Dishisha| first1 = Tarek| last2 = Alvarez| first2 = Maria Teresa| last3 = Hatti-Kaul| first3 = Rajni| url = http://lup.lub.lu.se/search/ws/files/4073436/4937831.pdf}}</ref><ref>{{cite journal | doi = 10.1002/bit.20473| pmid = 15977254| title = Enhanced propionic acid fermentation by ''Propionibacterium'' acidipropionici mutant obtained by adaptation in a fibrous-bed bioreactor| journal = Biotechnology and Bioengineering| volume = 91| issue = 3| pages = 325–337| year = 2005| last1 = Suwannakham| first1 = Supaporn| last2 = Yang| first2 = Shang-Tian}}</ref>
+Alternative methods of production have been trialled, by genetically engineering strains of ''[[Escherichia coli]]'' to incorporate the necessary pathway, the Wood-Werkman cycle.<ref>{{cite journal |doi=10.1002/bit.27182 |title=Engineering Escherichia coli for propionic acid production through the Wood–Werkman cycle |year=2020 |last1=Gonzalez‐Garcia |first1=Ricardo A. |last2=McCubbin |first2=Timothy |last3=Turner |first3=Mark S. |last4=Nielsen |first4=Lars K. |last5=Marcellin |first5=Esteban |journal=Biotechnology and Bioengineering |volume=117 |issue=1 |pages=167–183 |pmid=31556457 |s2cid=203438727 }}</ref>
-Propionic acid is produced biologically as its coenzyme A ester, [[propionyl-CoA]], from the [[metabolism|metabolic]] breakdown of fatty acids containing [[odd number]]s of [[carbon]] atoms, and also from the breakdown of some [[amino acid]]s. [[Bacteria]] of the genus ''[[Propionibacterium]]'' produce propionic acid as the end-product of their [[anaerobic respiration|anaerobic]] metabolism.  This class of bacteria is commonly found in the stomachs of [[ruminant]]s and the [[Cutibacterium acnes|sweat glands of humans]], and their activity is partially responsible for the odor of [[Emmental cheese]], [[Swiss cheese (North America)|American "Swiss cheese"]] and [[sweat]].
-Biotechnological production of propionic acid is mainly studied by the use of ''Propionibacterium'' strains. However, production of propionic acid by ''Propionibacteria'' is facing challenges such as severe inhibition of end-products during cell growth and the formation of by-products (acetic acid and succinic acid).<ref>{{Cite journal|doi = 10.3109/07388551.2011.651428|pmid = 22299651|title = Microbial production of propionic acid from propionibacteria: Current state, challenges and perspectives|journal = Critical Reviews in Biotechnology|volume = 32|issue = 4|pages = 374–381|year = 2012|last1 = Liu|first1 = Long|last2 = Zhu|first2 = Yunfeng|last3 = Li|first3 = Jianghua|last4 = Wang|first4 = Miao|last5 = Lee|first5 = Pengsoon|last6 = Du|first6 = Guocheng|last7 = Chen|first7 = Jian|s2cid = 25823025}}</ref> 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.<ref>{{cite journal | doi = 10.1007/s00253-015-6517-1| pmid = 25776062| title = A novel approach to monitor stress-induced physiological responses in immobilized microorganisms| journal = Applied Microbiology and Biotechnology| volume = 99| issue = 8| pages = 3573–3583| year = 2015| last1 = Alonso| first1 = Saúl| last2 = Rendueles| first2 = Manuel| last3 = Díaz| first3 = Mario| s2cid = 860853}}</ref> 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 capable to promote high density cell attachment and propionic acid production, which could be adapted to other fermentation bioprocesses.<ref>{{cite journal | doi = 10.1016/j.biortech.2017.10.087| pmid = 29136932| title = Cell immobilization on 3D-printed matrices: A model study on propionic acid fermentation| journal = Bioresource Technology| volume = 249| pages = 777–782| year = 2018| last1 = Belgrano| first1 = Fabricio dos Santos| last2 = Diegel| first2 = Olaf| last3 = Pereira| first3 = Nei| last4 = Hatti-Kaul| first4 = Rajni}}</ref> Other cell immobilization matrices have been tested, such as recycled-glass Poraver and fibrous-bed bioreactor.<ref>{{cite journal | doi = 10.1016/j.biortech.2012.05.079| pmid = 22728152| title = Batch- and continuous propionic acid production from glycerol using free and immobilized cells of Propionibacterium acidipropionici| journal = Bioresource Technology| volume = 118| pages = 553–562| year = 2012| last1 = Dishisha| first1 = Tarek| last2 = Alvarez| first2 = Maria Teresa| last3 = Hatti-Kaul| first3 = Rajni| url = http://lup.lub.lu.se/search/ws/files/4073436/4937831.pdf}}</ref><ref>{{cite journal | doi = 10.1002/bit.20473| pmid = 15977254| title = Enhanced propionic acid fermentation by ''Propionibacterium'' acidipropionici mutant obtained by adaptation in a fibrous-bed bioreactor| journal = Biotechnology and Bioengineering| volume = 91| issue = 3| pages = 325–337| year = 2005| last1 = Suwannakham| first1 = Supaporn| last2 = Yang| first2 = Shang-Tian}}</ref>
-It is also biosynthesized in the [[large intestine]] of humans by bacterial [[fermentation]] of [[dietary fibre]].<ref name = metab>{{cite journal|last1=den Besten |first1=G |last2=van Eunen |first2=K |last3=Groen |first3=AK |last4=Venema |first4=K|last5=Reijngoud|first5=DJ|last6=Bakker|first6=BM|title=The role of short-chain fatty acids in the interplay between diet, gut microbiota, and host energy metabolism.|journal=Journal of Lipid Research|date=September 2013|volume=54|issue=9|pages=2325–40|doi=10.1194/jlr.R036012|pmid=23821742|pmc=3735932}}</ref>
 ==Industrial uses==
-Propionic acid inhibits the growth of [[Mold (fungus)|mold]] and some [[bacteria]] at the levels between 0.1 and 1% by weight.  As a result, most 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 [[Propionibacterium|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.<ref name=Ullmann/> As a [[food additive]], it is approved for use in the EU,<ref>{{cite web | url = http://www.food.gov.uk/safereating/chemsafe/additivesbranch/enumberlist | title = Current EU approved additives and their E Numbers | publisher = UK Food Standards Agency | accessdate=2011-10-27 }}</ref> USA,<ref>{{ cite web | url = https://www.fda.gov/Food/FoodIngredientsPackaging/FoodAdditives/ucm191033.htm#ftnT | title = Listing of Food Additives Status Part II | publisher = US Food and Drug Administration | accessdate=2011-10-27 }}</ref> Australia and New Zealand.<ref>{{cite web | url = http://www.comlaw.gov.au/Details/F2011C00827 | title = Standard 1.2.4 – Labelling of ingredients | work = Australia New Zealand Food Standards Code | publisher = Comlaw.au | accessdate=2011-10-27 }}</ref>
+Propionic acid inhibits the growth of [[Mold (fungus)|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 [[Propionibacterium|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.<ref name=Ullmann/> As a [[food additive]], it is approved for use in the EU,<ref>{{cite web | url = http://www.food.gov.uk/safereating/chemsafe/additivesbranch/enumberlist | title = Current EU approved additives and their E Numbers | publisher = UK Food Standards Agency | accessdate=2011-10-27 }}</ref> USA,<ref>{{ cite web | url = https://www.fda.gov/Food/FoodIngredientsPackaging/FoodAdditives/ucm191033.htm#ftnT | title = Listing of Food Additives Status Part II | publisher = US Food and Drug Administration | accessdate=2011-10-27 }}</ref> Australia and New Zealand.<ref>{{cite web | url = http://www.comlaw.gov.au/Details/F2011C00827 | title = Standard 1.2.4 – Labelling of ingredients | work = Australia New Zealand Food Standards Code | publisher = Comlaw.au | accessdate=2011-10-27 }}</ref>
-Propionic acid is also useful as an intermediate in the production of other chemicals, especially polymers. [[Cellulose]]-[[acetate-propionate]] is a useful [[thermoplastic]].  [[Vinyl propionate]] is also used.  In more specialized applications, it is also used to make [[pesticide]]s and [[pharmaceutical]]s.  The [[ester]]s of propionic acid have fruit-like odors and are sometimes used as [[solvent]]s or artificial flavorings.<ref name=Ullmann/>
+Propionic acid is also useful as an intermediate in the production of other chemicals, especially polymers. [[Cellulose acetate|Cellulose-acetate-propionate]] is a useful [[thermoplastic]].  [[Vinyl propionate]] is also used.  In more specialized applications, it is also used to make [[pesticide]]s and [[pharmaceutical]]s.  The [[ester]]s of propionic acid have fruit-like odors and are sometimes used as [[solvent]]s or artificial flavorings.<ref name=Ullmann/>
-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.<ref name="Ahlert">{{cite journal|last1 = Ahlert|first1 = Stephan|last2 = Zimmermann|first2 = Rita|last3 = Ebling|first3 = Johannes|last4 = König|first4 = Helmut|year = 2016|title = Analysis of propionate-degrading consortia from agricultural biogas plants|journal = [[MicrobiologyOpen]]|doi = 10.1002/mbo3.386|pmid = 27364538|pmc = 5221444|doi-access = free|volume = 5|issue = 6|pages = 1027–1037}}</ref>
+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.<ref name="Ahlert">{{cite journal|last1 = Ahlert|first1 = Stephan|last2 = Zimmermann|first2 = Rita|last3 = Ebling|first3 = Johannes|last4 = König|first4 = Helmut|year = 2016|title = Analysis of propionate-degrading consortia from agricultural biogas plants|journal = MicrobiologyOpen |doi = 10.1002/mbo3.386|pmid = 27364538|pmc = 5221444|doi-access = free|volume = 5|issue = 6|pages = 1027–1037}}</ref>
+==Biology==
+Propionic acid is produced biologically as its coenzyme A ester, [[propionyl-CoA]], from the [[metabolism|metabolic]] breakdown of fatty acids containing [[odd number]]s of [[carbon]] atoms, and also from the breakdown of some [[amino acid]]s. [[Bacteria]] of the genus ''Propionibacterium'' produce propionic acid as the end-product of their [[anaerobic respiration|anaerobic]] metabolism.  This class of bacteria is commonly found in the stomachs of [[ruminant]]s and the [[Cutibacterium acnes|sweat glands of humans]], and their activity is partially responsible for the odor of [[Emmental cheese]], [[Swiss cheese (North America)|American "Swiss cheese"]] and [[sweat]].
-==Biological uses==
 The metabolism of propionic acid begins with its conversion to propionyl [[coenzyme A]], the usual first step in the metabolism of [[carboxylic acid]]s.  Since propionic acid has three carbons, propionyl-CoA cannot directly enter either [[beta oxidation]] or the [[citric acid cycle]]s.  In most [[vertebrate]]s, propionyl-CoA is [[carboxylation|carboxylated]] to <small>D</small>-[[methylmalonyl-CoA]], which is [[Isomerisation|isomerised]] to <small>L</small>-methylmalonyl-CoA. A [[vitamin B12|vitamin B<sub>12</sub>]]-dependent enzyme catalyzes rearrangement of <small>L</small>-methylmalonyl-CoA to [[succinyl-CoA]], which is an intermediate of the citric acid cycle and can be readily incorporated there.
 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.<ref name = macfabe>{{cite journal
-|author1=D. F. MacFabe |author2=D. P. Cain |author3=K. Rodriguez-Capote |author4=A. E. Franklin |author5=J. E. Hoffman |author6=F. Boon |author7=A. R. Taylor |author8=M. Kavaliers |author9=K.-P. Ossenkopp | journal = Behavioural Brain Research | title = Neurobiological effects of intraventricular propionic acid in rats: Possible role of short-chain fatty acids on the pathogenesis and characteristics of autism spectrum disorders | year = 2007 | volume = 176 | issue = 1 | pages = 149–169 | doi = 10.1016/j.bbr.2006.07.025 |pmid=16950524 |s2cid=3054752 | url = }}</ref><ref>{{cite journal |author1=N. H. T. Nguyen |author2=C. Morland |author3=S. Villa Gonzalez |author4=F. Rise |author5=J. Storm-Mathisen |author6=V. Gundersen |author7=B. Hassel | journal = Journal of Neurochemistry | title = Propionate increases neuronal histone acetylation, but is metabolized oxidatively by glia. Relevance for propionic acidemia | year = 2007 | volume = 101 | pmid = 17286595 | issue = 3 | pages = 806–814 | doi = 10.1111/j.1471-4159.2006.04397.x | url =  }}</ref>  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.<ref name = macfabe/>
+|author1=D. F. MacFabe |author2=D. P. Cain |author3=K. Rodriguez-Capote |author4=A. E. Franklin |author5=J. E. Hoffman |author6=F. Boon |author7=A. R. Taylor |author8=M. Kavaliers |author9=K.-P. Ossenkopp | journal = Behavioural Brain Research | title = Neurobiological effects of intraventricular propionic acid in rats: Possible role of short-chain fatty acids on the pathogenesis and characteristics of autism spectrum disorders | year = 2007 | volume = 176 | issue = 1 | pages = 149–169 | doi = 10.1016/j.bbr.2006.07.025 |pmid=16950524 | url = }}</ref><ref>{{cite journal |author1=N. H. T. Nguyen |author2=C. Morland |author3=S. Villa Gonzalez |author4=F. Rise |author5=J. Storm-Mathisen |author6=V. Gundersen |author7=B. Hassel | journal = Journal of Neurochemistry | title = Propionate increases neuronal histone acetylation, but is metabolized oxidatively by glia. Relevance for propionic acidemia | year = 2007 | volume = 101 | pmid = 17286595 | issue = 3 | pages = 806–814 | doi = 10.1111/j.1471-4159.2006.04397.x | url =  }}</ref>  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.<ref name = macfabe/>
 It also, being a three-carbon molecule, feeds into [[hepatic]] [[gluconeogenesis]] (that is, the creation of [[glucose]] molecules from simpler molecules in the liver).<ref>{{cite journal|last1=Aschenbach|first1=JR|last2=Kristensen|first2=NB|last3=Donkin|first3=SS|last4=Hammon|first4=HM|last5=Penner|first5=GB|title=Gluconeogenesis in dairy cows: the secret of making sweet milk from sour dough.|journal=IUBMB Life|date=December 2010|volume=62|issue=12|pages=869–77|doi=10.1002/iub.400|pmid=21171012}}</ref>
 ===Human occurrence===
+The human [[skin]] is host of several species of ''Propionibacteria''.  The most notable one is the ''[[Cutibacterium acnes]]'' (formerly known as ''Propionibacterium acnes''), which lives mainly in the [[sebaceous gland]]s of the skin and is one of the principal causes of [[acne]].<ref>{{cite journal |doi=10.1016/j.clindermatol.2004.03.005 |title=Acne and propionibacterium acnes |year=2004 |last1=Bojar |first1=Richard A. |last2=Holland |first2=Keith T. |journal=Clinics in Dermatology |volume=22 |issue=5 |pages=375–379 }}</ref> Propionate is observed to be among the most common [[short-chain fatty acid]]s produced in the [[large intestine]] of humans by [[gut microbiome|gut microbiota]] in response to indigestible carbohydrates ([[dietary fiber]]) in the diet.<ref>{{cite journal |last1=Cani |first1=Patrice D. |last2=Knauf |first2=Claude |title=How gut microbes talk to organs: The role of endocrine and nervous routes |journal=Molecular Metabolism |date=27 May 2016 |volume=5 |issue=9 |pages=743–752 |doi=10.1016/j.molmet.2016.05.011 |pmid=27617197 |pmc=5004142 }}</ref><ref name = metab>{{cite journal|last1=den Besten |first1=G |last2=van Eunen |first2=K |last3=Groen |first3=AK |last4=Venema |first4=K|last5=Reijngoud|first5=DJ|last6=Bakker|first6=BM|title=The role of short-chain fatty acids in the interplay between diet, gut microbiota, and host energy metabolism.|journal=Journal of Lipid Research|date=September 2013|volume=54|issue=9|pages=2325–40|doi=10.1194/jlr.R036012|pmid=23821742|pmc=3735932}}</ref> The role of the gut microbiota and their metabolites, including propionate, in mediating brain function has been reviewed.<ref>{{cite journal |doi=10.1038/mp.2016.50 |doi-access=free |title=From gut dysbiosis to altered brain function and mental illness: mechanisms and pathways }}</ref>
-The human [[skin]] is host of several species of bacteria known as ''[[Propionibacteria]]'', which are named after their ability to produce propionic acid.  The most notable one is the ''[[Cutibacterium acnes]]'' (formerly known as ''Propionibacterium acnes''), which lives mainly in the [[sebaceous gland]]s of the skin and is one of the principal causes of [[acne]].
+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.<ref>{{cite journal |doi=10.1016/j.chom.2018.07.002   |title=A Gut Commensal-Produced Metabolite Mediates Colonization Resistance to Salmonella Infection |year=2018 |last1=Jacobson |first1=Amanda |last2=Lam |first2=Lilian |last3=Rajendram |first3=Manohary |last4=Tamburini |first4=Fiona |last5=Honeycutt |first5=Jared |last6=Pham |first6=Trung |last7=Van Treuren |first7=Will |last8=Pruss |first8=Kali |last9=Stabler |first9=Stephen Russell |last10=Lugo |first10=Kyler |last11=Bouley |first11=Donna M. |last12=Vilches-Moure |first12=Jose G. |last13=Smith |first13=Mark |last14=Sonnenburg |first14=Justin L. |last15=Bhatt |first15=Ami S. |last16=Huang |first16=Kerwyn Casey |last17=Monack |first17=Denise |journal=Cell Host & Microbe |volume=24 |issue=2 |pages=296–307.e7 |pmid=30057174 }}</ref> 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.<ref>{{cite journal |doi=10.1161/CIRCULATIONAHA.118.036652 |title=Short-Chain Fatty Acid Propionate Protects from Hypertensive Cardiovascular Damage |year=2019 |last1=Bartolomaeus |first1=Hendrik |last2=Balogh |first2=András |last3=Yakoub |first3=Mina |last4=Homann |first4=Susanne |last5=Markó |first5=Lajos |last6=Höges |first6=Sascha |last7=Tsvetkov |first7=Dmitry |last8=Krannich |first8=Alexander |last9=Wundersitz |first9=Sebastian |last10=Avery |first10=Ellen G. |last11=Haase |first11=Nadine |last12=Kräker |first12=Kristin |last13=Hering |first13=Lydia |last14=Maase |first14=Martina |last15=Kusche-Vihrog |first15=Kristina |last16=Grandoch |first16=Maria |last17=Fielitz |first17=Jens |last18=Kempa |first18=Stefan |last19=Gollasch |first19=Maik |last20=Zhumadilov |first20=Zhaxybay |last21=Kozhakhmetov |first21=Samat |last22=Kushugulova |first22=Almagul |last23=Eckardt |first23=Kai-Uwe |last24=Dechend |first24=Ralf |last25=Rump |first25=Lars Christian |last26=Forslund |first26=Sofia K. |last27=Müller |first27=Dominik N. |last28=Stegbauer |first28=Johannes |last29=Wilck |first29=Nicola |journal=Circulation |volume=139 |issue=11 |pages=1407–1421 |pmid=30586752 |pmc=6416008 }}</ref>
+=== Bacteriology ===
+The Bacteria species ''Coprothermobacter platensis'' produces propionate when fermenting gelatin.<ref>{{Cite journal|last=Etchebehere|first=C.|last2=Pavan|first2=M. E.|last3=Zorzópulos|first3=J.|last4=Soubes|first4=M.|last5=Muxí|first5=L.|date=October 1998|title=Coprothermobacter platensis sp. nov., a new anaerobic proteolytic thermophilic bacterium isolated from an anaerobic mesophilic sludge|journal=International Journal of Systematic Bacteriology|volume=48 Pt 4|issue=4|pages=1297–1304|doi=10.1099/00207713-48-4-1297|issn=0020-7713|pmid=9828430|doi-access=free}}</ref>
+== Propionate salts and esters ==
+The '''propionate''' {{IPAc-en|'|p|r|oʊ|p|i|ə|n|eɪ|t}}, or '''propanoate''',  [[ion]] is [[Carbon|C]]<sub>2</sub>[[Hydrogen|H]]<sub>5</sub>C[[Oxygen|O]]O<sup>&minus;</sup>, the [[conjugate base]] of propionic acid. It is the form found in biological systems at [[physiological pH]]. A propionic, or propanoic, compound is a [[Salt (chemistry)|salt]] or [[ester]] of propionic acid. In these compounds, propionate is often written in shorthand, as CH<sub>3</sub>CH<sub>2</sub>CO<sub>2</sub> or simply EtCO<sub>2</sub>.
+Propionates should not be confused with propenoates (commonly known as [[acrylate]]s), the ions/salts/esters of propenoic acid (also known as 2-propenoic acid or [[acrylic acid]]).
+===Examples===
+====Salts====
+*[[Sodium propionate]] NaC<sub>2</sub>H<sub>5</sub>CO<sub>2</sub>
+*[[Potassium propionate]] KC<sub>2</sub>H<sub>5</sub>CO<sub>2</sub>
+*[[Calcium propionate]] Ca(C<sub>2</sub>H<sub>5</sub>CO<sub>2</sub>)<sub>2</sub>
+*[[Zirconium propionate]] Zr(C<sub>2</sub>H<sub>5</sub>CO<sub>2</sub>)<sub>4</sub>
+====Esters====
+*[[Methyl propionate]] (C<sub>2</sub>H<sub>5</sub>(CO)OCH<sub>3</sub>)
+*[[Ethyl propionate]] (C<sub>2</sub>H<sub>5</sub>(CO)OC<sub>2</sub>H<sub>5</sub>)
+*[[Propyl propionate]] (C<sub>2</sub>H<sub>5</sub>(CO)OC<sub>3</sub>H<sub>7</sub>)
+*[[Pentyl propionate]] (C<sub>2</sub>H<sub>5</sub>(CO)OC<sub>5</sub>H<sub>11</sub>)
+*[[Fluticasone propionate]] C<sub>25</sub>H<sub>31</sub>F<sub>3</sub>O<sub>5</sub>S
 ==See also==
 * [[List of saturated fatty acids]]
@@ Line 161: / Line 190: @@
 ==External links==
 {{Commons category|Propionic acid}}
-* [http://webbook.nist.gov/chemistry/ NIST Standard Reference Database]
+* [https://webbook.nist.gov/cgi/inchi/InChI%3D1S/C3H6O2/c1-2-3(4)5/h2H2%2C1H3%2C(H%2C4%2C5) NIST Standard Reference Data for propanic acid]
 * [http://www.inchem.org/documents/icsc/icsc/eics0806.htm International Chemical Safety Card 0806]
 * [https://www.cdc.gov/niosh/npg/npgd0529.html NIOSH Pocket Guide to Chemical Hazards]
-* [http://www.basf.com/static/OpenMarket/Xcelerate/Preview_cid-974236976155_pubid-974236725646_c-Article.html  Technical data of propionic acid of BASF]
-* [http://www.psychology.uwo.ca/pdfs/autism/MacFabe%20etal07.pdf Neurobiological effects of intraventricular propionic acid in ratsPossible role of short chain fatty acids on the pathogenesis and characteristics of autism spectrum disorders]
 * [http://tpx.sagepub.com/content/16/2/245.full.pdf The Propionic Acids. Gastrointestinal Toxicity in Various Species]
 * [https://web.archive.org/web/20130619080113/http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_08ac/0901b803808ac9fd.pdf?filepath=oxysolvents%2Fpdfs%2Fnoreg%2F327-00019.pdf&fromPage=GetDoc Propionic Acid Technical Data Sheet]
 {{Fatty acids}}
 {{Authority control}}
 {{DEFAULTSORT:Propionic Acid}}
 [[Category:Propionic acids| ]]

v t e Lipids: fatty acids
Saturated	Propionic (C3) Butyric (C4) Valeric (C5) Caproic (C6) Enanthic (C7) Caprylic (C8) Pelargonic (C9) Capric (C10) Undecylic (C11) Lauric (C12) Tridecylic (C13) Myristic (C14) Pentadecylic (C15) Palmitic (C16) Margaric (C17) Stearic (C18) Nonadecylic (C19) Arachidic (C20) Heneicosylic (C21) Behenic (C22) Tricosylic (C23) Lignoceric (C24) Pentacosylic (C25) Cerotic (C26) Carboceric (C27) Montanic (C28) Nonacosylic (C29) Melissic (C30) Hentriacontylic (C31) Lacceroic (C32) Psyllic (C33) Geddic (C34) Ceroplastic (C35) Hexatriacontylic (C36) Heptatriacontanoic (C37) Octatriacontanoic (C38) Nonatriacontanoic (C39) Tetracontanoic (C40)
ω−3 Unsaturated	Octenoic (8:1) Decenoic (10:1) Decadienoic (10:2) Lauroleic (12:1) Laurolinoleic (12:2) Myristovaccenic (14:1) Myristolinoleic (14:2) Myristolinolenic (14:3) Palmitolinolenic (16:3) Palmitidonic (16:4) α-Linolenic (18:3) Stearidonic (18:4) α-Parinaric (18:4) Dihomo-α-linolenic (20:3) Eicosatetraenoic (20:4) Eicosapentaenoic (20:5) Clupanodonic (22:5) Docosahexaenoic (22:6) 9,12,15,18,21-Tetracosapentaenoic (24:5) 6,9,12,15,18,21-Tetracosahexaenoic (24:6)
ω−5 Unsaturated	Myristoleic (14:1) Palmitovaccenic (16:1) α-Eleostearic (18:3) β-Eleostearic (trans-18:3) Punicic (18:3) 7,10,13-Octadecatrienoic (18:3) 9,12,15-Eicosatrienoic (20:3) β-Eicosatetraenoic (20:4)
ω−6 Unsaturated	8-Tetradecenoic (14:1) 12-Octadecenoic (18:1) Linoleic (18:2) Linolelaidic (trans-18:2) γ-Linolenic (18:3) Calendic (18:3) Pinolenic (18:3) Dihomo-linoleic (20:2) Dihomo-γ-linolenic (20:3) Sciadonic (20:3) Arachidonic (20:4) Adrenic (22:4) Osbond (22:5)
ω−7 Unsaturated	Palmitoleic (16:1) Vaccenic (18:1) Rumenic (18:2) Paullinic (20:1) 7,10,13-Eicosatrienoic (20:3)
ω−9 Unsaturated	Oleic (18:1) Elaidic (trans-18:1) Gondoic (20:1) Erucic (22:1) Nervonic (24:1) 8,11-Eicosadienoic (20:2) Mead (20:3)
ω−10 Unsaturated	Sapienic (16:1)
ω−11 Unsaturated	Gadoleic (20:1)
ω−12 Unsaturated	4-Hexadecenoic (16:1) Petroselinic (18:1) 8-Eicosenoic (20:1)