- Butyric acid
Chembox new
ImageFile =Butyric-acid-2D-skeletal.png
ImageName = Skeletal structure
ImageSize = 140 px
ImageFile1 = Butyric_acid_flat_structure.png
ImageName1 = Flat structure
ImageSize1 = 160 px
ImageFile2 = Butyric-acid-3D-balls.png
ImageName = Space filling model
ImageSize2 = 150px
IUPACName = Butanoic acid
Section1 = Chembox Identifiers
CASNo=107-92-6
PubChem=264
ChemSpiderID = 259
SMILES=CCCC(=O)O
MeSHName=Butyric+acid
Section2= Chembox Properties
Formula=C4H8O2
MolarMass=88.1051 g/mol
Appearance=
Density=0.96 g/mL
MeltingPt=-7.9 °C (265.1 K)
BoilingPt=163.5 °C (436.5 K)
Solubility=miscible
Section3= Chembox Hazards
MainHazards=Corrosive; Harmful to aquatic organisms
FlashPt=72 °C
Autoignition=452 °C
RPhrases = 34
SPhrases = 26 36 45
RSPhrases =
RTECS = ES5425000Butyric acid (from Greek βούτυρος = "butter"), also known under the systematic name butanoic acid, is a
carboxylic acid with the structural formula CH3CH2CH2-COOH. It is found in rancidbutter ,parmesan cheese ,vomit , andbody odor and has an unpleasant smell and acridtaste , with a sweetish aftertaste (similar to ether). Butyric acid can be detected bymammal s with good scent detection abilities such asdog s at 10ppb , whereashuman s can detect it in concentrations above 10 ppm.Chemistry
Butyric acid is a
fatty acid occurring in the form ofesters in animal fats and plant oils. The triglyceride of butyric acid makes up 3% to 4% of butter. When butter goes rancid, butyric acid is liberated from the glyceride byhydrolysis leading to the unpleasant odor. It is an important member of the fatty acid sub-group calledshort chain fatty acids . Butyric acid is aweak acid with apKa of 4.82, similar toacetic acid which has pKa 4.76. [cite web|url=http://www.linkan.se/files/pdf/product_sheets/INVE/adimix_presentation.pdf|title=Adimix Sodium Butanoate information] The similar strength of these acids results from their common -CH2COOH terminal structure. [cite web|url=http://web.chem.ucla.edu/~harding/tutorials/acids_and_bases/pKa_table.html|title=Using the pKa table] Pure butyric acid is 10.9 molar.The acid is an oily colorless liquid that is easily soluble in
water ,ethanol , andether , and can be separated from an aqueous phase by saturation with saslts such ascalcium chloride .Potassium dichromate andsulfuric acid oxidize it tocarbon dioxide andacetic acid , while alkalinepotassium permanganate oxidizes it to carbon dioxide. The calcium salt, Ca(C4H7O2)2·H2O, is less soluble in hot water than in cold.Butyric acid has a
structural isomer calledisobutyric acid (2-methylpropanoic acid).Production
It is industrially prepared by the fermentation of
sugar orstarch , brought about by the addition of putrefyingcheese , withcalcium carbonate added to neutralize the acids formed in the process. The butyric fermentation of starch is aided by the direct addition of "Bacillus subtilis ". Salts and esters of the acid are calledbutanoate s.Butyric acid or fermentation butyric acid is also found as a hexyl
ester (hexyl butanoate) in the oil of "Heracleum giganteum" (a type ofcow parsnip ) and as an octyl ester (octyl butanoate) inparsnip ("Pastinaca sativa"); it has also been noticed in the fluids of the flesh and in perspiration.Uses
Butyric acid is used in the preparation of various butanoate esters. Low-molecular-weight esters of butyric acid, such as
methyl butanoate , have mostly pleasant aromas or tastes. As a consequence, they find use as food and perfume additives. They are also used in organic laboratory courses, to teach the Fischer esterification reaction.Biological functionality
Butanoate fermentation
Butanoate is produced as end-product of a fermentation process solely performed by obligate anaerobic
bacteria . FermentedKombucha "tea" includes butyric acid as a result of the fermentation. This fermentation pathway was discovered byLouis Pasteur in1861 . Examples of butanoate-producingspecies of bacteria:* "
Clostridium acetobutylicum "
* "Clostridium butyricum "
* "Clostridium kluyveri "
* "Clostridium pasteurianum "
* "Fusobacterium nucleatum "
* "Butyrivibrio fibrisolvens "
* "Eubacterium limosum "The pathway starts with the glycolytic cleavage of
glucose to twomolecule s ofpyruvate , as happens in most organisms. Pyruvate is then oxidized intoacetyl coenzyme A using a unique mechanism that involves anenzyme system calledpyruvate-ferredoxin oxidoreductase . Two molecules ofcarbon dioxide (CO2) and two molecules of elementalhydrogen (H2) are formed as wastes products from the cell. Then:ATP is produced, as can be seen, in the last step of the fermentation. Three molecules of ATP are produced for each glucose molecule, a relatively high yield. The balanced equation for this fermentation is:
C6H12O6 → C4H8O2 + 2CO2 + 2H2
Acetone and butanol fermentation
Several species form
acetone andbutanol in an alternative pathway, which starts as butyrate fermentation. Some of these species are:* "
Clostridium acetobutylicum ": the most prominent acetone and butanol producer, used also in industry
* "Clostridium beijerinckii "
* "Clostridium tetanomorphum "
* "Clostridium aurantibutyricum "These bacteria begin with butanoate fermentation as described above, but, when the
pH drops below 5, they switch into butanol and acetone production in order to prevent further lowering of the pH. Two molecules of butanol are formed for each molecule of acetone.The change in the pathway occurs after acetoacetyl CoA formation. This intermediate then takes two possible pathways:
* Acetoacetyl CoA → acetoacetate → acetone, or
* Acetoacetyl CoA → butyryl CoA →butanal → butanol.Butyric acid function/activity
Highly-fermentable fibers like
oat bran ,pectin , andguar are transformed by colonic bacteria intoshort chain fatty acid s including butyrate.Butanoate has diverse and, it seems, paradoxical effects on cellular proliferation,
apoptosis and differentiation that may be either pro-neoplastic or anti-neoplastic, depending upon factors such as the level of exposure, availability of other metabolic substrate, and the intracellular milieu. Butanoate is thought by some to be protective againstcolon cancer . However, not all studies support a chemopreventive effect, and the lack of agreement (particularly betweenin vivo andin vitro studies) on butyrate and colon cancer has been termed the "butyrate paradox." There are many reasons for this discrepant effect, including differences between the "in vitro" and "in vivo" environments, the timing of butanoate administration, the amount administered, the source (usually dietary fiber) as a potential confounder, and an interaction with dietary fat. Together, the studies suggest that the chemopreventive benefits of butanoate depend in part on amount, time of exposure with respect to the tumorigenic process, and the type of fat in the diet. [ [http://jn.nutrition.org/cgi/content/full/134/2/479 Microbial Degradation Products Influence Colon Cancer Risk: the Butyrate Controversy - Lupton 134 (2): 479 - Journal of Nutrition ] ] Low carbohydrate diets like theAtkins diet are known to reduce the amount of butanoate produced in the colon.Butyric acid has been associated with the ability to inhibit the function of
histone deacetylase enzymes, thereby favouring an acetylated state ofhistone s in the cell. Acetylated histones have a lower affinity forDNA than non-acetylated histones, due to the neutralisation ofelectrostatic charge interactions. In general, it is thought thattranscription factors will be unable to access regions where histones are tightly associated with DNA (ie non-acetylated, e.g., heterochromatin). Therefore, it is thought that butyric acid enhances the transcriptional activity at promoters, which are typically silenced/downregulated due to histone deacetylase activity.References
See also
*
Indole-3-butyric acid
*Acids in wine External links
* [http://www.cdc.gov/niosh/ipcsneng/neng1334.html International Chemical Safety Card 1334]
* [http://jn.nutrition.org/cgi/content/full/134/2/479 2004 review of the scientific evidence on butanoate/butyrate vs. colon cancer]"This article incorporates information from the 1911 encyclopedia."
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