Acetoin

Last updated
Acetoin
Acetoin-2D.svg
Names
Preferred IUPAC name
3-Hydroxybutan-2-one
Other names
3-Hydroxybutanone
Acetyl methyl carbinol
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.007.432 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 208-174-1
KEGG
PubChem CID
RTECS number
  • EL8790000
UNII
  • InChI=1S/C4H8O2/c1-3(5)4(2)6/h3,5H,1-2H3 Yes check.svgY
    Key: ROWKJAVDOGWPAT-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C4H8O2/c1-3(5)4(2)6/h3,5H,1-2H3
    Key: ROWKJAVDOGWPAT-UHFFFAOYAD
  • CC(=O)C(C)O
  • (R):CC(=O)[C@@H](C)O
  • (S):CC(=O)[C@H](C)O
Properties
C4H8O2
Molar mass 88.106 g·mol−1
Appearancecolorless liquid
Odor bland, yogurt-like
Density 1.012 g/cm3
Melting point 15 °C (59 °F; 288 K)
Boiling point 148 °C (298 °F; 421 K)
1000 g/L (20 °C)
Solubility in other solventsSoluble in alcohol
Slightly soluble in ether, petroleum ether
Miscible in propylene glycol
Insoluble in vegetable oil
log P -0.36
Acidity (pKa)13.72
-39.4
1.4171
Hazards
Flash point 41 °C (106 °F; 314 K)
Lethal dose or concentration (LD, LC):
> 5000 mg/kg (rat, oral)
Safety data sheet (SDS) MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Acetoin, also known as 3-hydroxybutanone or acetyl methyl carbinol, is an organic compound with the formula CH3CH(OH)C(O)CH3. It is a colorless liquid with a pleasant, buttery odor. It is chiral. The form produced by bacteria is (R)-acetoin. [1]

Contents

Production in bacteria

Acetoin is a neutral, four-carbon molecule used as an external energy store by a number of fermentative bacteria. It is produced by the decarboxylation of alpha-acetolactate, a common precursor in the biosynthesis of branched-chain amino acids. Owing to its neutral nature, production and excretion of acetoin during exponential growth prevents over-acidification of the cytoplasm and the surrounding medium that would result from accumulation of acidic metabolic products, such as acetic acid and citric acid. Once superior carbon sources are exhausted, and the culture enters stationary phase, acetoin can be used to maintain the culture density. [2] The conversion of acetoin into acetyl-CoA is catalysed by the acetoin dehydrogenase complex, following a mechanism largely analogous to the pyruvate dehydrogenase complex; however, as acetoin is not a 2-oxoacid, it does not undergo decarboxylation by the E1 enzyme; instead, a molecule of acetaldehyde is released. [3] In some bacteria, acetoin can also be reduced to 2,3-butanediol by acetoin reductase/2,3-butanediol dehydrogenase.

The Voges-Proskauer test is a commonly used microbiological test for acetoin production. [4]

Uses

Food ingredients

Acetoin, along with diacetyl, is one of the compounds that gives butter its characteristic flavor. Because of this, manufacturers of partially hydrogenated oils typically add artificial butter flavor – acetoin and diacetyl – (along with beta carotene for the yellow color) to the final product. [5]

Acetoin can be found in apples, yogurt, asparagus, blackcurrants, blackberries, wheat, broccoli, brussels sprouts, cantaloupes, and maple syrup. [6] [7] [8]

Acetoin is used as a food flavoring (in baked goods) and as a fragrance.

Electronic cigarettes

It is used in liquids for electronic cigarettes to give a buttery or caramel flavor. [9]

See also

Related Research Articles

<span class="mw-page-title-main">Citric acid cycle</span> Interconnected biochemical reactions releasing energy

The citric acid cycle—also known as the Krebs cycle, Szent–Györgyi–Krebs cycle or the TCA cycle (tricarboxylic acid cycle)—is a series of biochemical reactions to release the energy stored in nutrients through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins. The chemical energy released is available under the form of ATP. The Krebs cycle is used by organisms that respire (as opposed to organisms that ferment) to generate energy, either by anaerobic respiration or aerobic respiration. In addition, the cycle provides precursors of certain amino acids, as well as the reducing agent NADH, that are used in numerous other reactions. Its central importance to many biochemical pathways suggests that it was one of the earliest components of metabolism. Even though it is branded as a "cycle", it is not necessary for metabolites to follow only one specific route; at least three alternative segments of the citric acid cycle have been recognized.

<span class="mw-page-title-main">Acetyl-CoA</span> Chemical compound

Acetyl-CoA is a molecule that participates in many biochemical reactions in protein, carbohydrate and lipid metabolism. Its main function is to deliver the acetyl group to the citric acid cycle to be oxidized for energy production.

<span class="mw-page-title-main">Diacetyl</span> Chemical compound

Diacetyl ( dy-yuh-SEE-tuhl; IUPAC systematic name: butanedione or butane-2,3-dione) is an organic compound with the chemical formula (CH3CO)2. It is a yellow liquid with an intensely buttery flavor. It is a vicinal diketone (two C=O groups, side-by-side). Diacetyl occurs naturally in alcoholic beverages and is added as a flavoring to some foods to impart its buttery flavor.

<span class="mw-page-title-main">Pyruvate dehydrogenase complex</span> Three-enzyme complex

Pyruvate dehydrogenase complex (PDC) is a complex of three enzymes that converts pyruvate into acetyl-CoA by a process called pyruvate decarboxylation. Acetyl-CoA may then be used in the citric acid cycle to carry out cellular respiration, and this complex links the glycolysis metabolic pathway to the citric acid cycle. Pyruvate decarboxylation is also known as the "pyruvate dehydrogenase reaction" because it also involves the oxidation of pyruvate.

<span class="mw-page-title-main">Malolactic fermentation</span> Process in winemaking

Malolactic conversion is a process in winemaking in which tart-tasting malic acid, naturally present in grape must, is converted to softer-tasting lactic acid. Malolactic fermentation is most often performed as a secondary fermentation shortly after the end of the primary fermentation, but can sometimes run concurrently with it. The process is standard for most red wine production and common for some white grape varieties such as Chardonnay, where it can impart a "buttery" flavor from diacetyl, a byproduct of the reaction.

Acetogenesis is a process through which acetate is produced by prokaryote microorganisms either by the reduction of CO2 or by the reduction of organic acids, rather than by the oxidative breakdown of carbohydrates or ethanol, as with acetic acid bacteria.

<span class="mw-page-title-main">Butanediol fermentation</span> Chemical reaction

2,3-Butanediol fermentation is anaerobic fermentation of glucose with 2,3-butanediol as one of the end products. The overall stoichiometry of the reaction is

<span class="mw-page-title-main">Mixed acid fermentation</span> Biochemical conversion of six-carbon sugars into acids in bacteria

In biochemistry, mixed acid fermentation is the metabolic process by which a six-carbon sugar is converted into a complex and variable mixture of acids. It is an anaerobic (non-oxygen-requiring) fermentation reaction that is common in bacteria. It is characteristic for members of the Enterobacteriaceae, a large family of Gram-negative bacteria that includes E. coli.

Oxidative decarboxylation is a decarboxylation reaction caused by oxidation. Most are accompanied by α- Ketoglutarate α- Decarboxylation caused by dehydrogenation of hydroxyl carboxylic acids such as carbonyl carboxylic acid, malic acid, isocitric acid, etc.

In biochemistry, fatty acid synthesis is the creation of fatty acids from acetyl-CoA and NADPH through the action of enzymes called fatty acid synthases. This process takes place in the cytoplasm of the cell. Most of the acetyl-CoA which is converted into fatty acids is derived from carbohydrates via the glycolytic pathway. The glycolytic pathway also provides the glycerol with which three fatty acids can combine to form triglycerides, the final product of the lipogenic process. When only two fatty acids combine with glycerol and the third alcohol group is phosphorylated with a group such as phosphatidylcholine, a phospholipid is formed. Phospholipids form the bulk of the lipid bilayers that make up cell membranes and surrounds the organelles within the cells. In addition to cytosolic fatty acid synthesis, there is also mitochondrial fatty acid synthesis (mtFASII), in which malonyl-CoA is formed from malonic acid with the help of malonyl-CoA synthetase (ACSF3), which then becomes the final product octanoyl-ACP (C8) via further intermediate steps.

<span class="mw-page-title-main">(R,R)-butanediol dehydrogenase</span> Class of enzymes

In enzymology, a (R,R)-butanediol dehydrogenase (EC 1.1.1.4) is an enzyme that catalyzes the chemical reaction

In enzymology, a (S,S)-butanediol dehydrogenase (EC 1.1.1.76) is an enzyme that catalyzes the chemical reaction

In enzymology, an acetoin racemase is an enzyme that catalyzes the chemical reaction

<span class="mw-page-title-main">IMViC</span> Microbiological and biochemical method for identification

The IMViC tests are a group of individual tests used in microbiology lab testing to identify an organism in the coliform group. A coliform is a gram negative, aerobic, or facultative anaerobic rod, which produces gas from lactose within 48 hours. The presence of some coliforms indicate fecal contamination.

Voges–Proskauer or VP is a test used to detect acetoin in a bacterial broth culture. The test is performed by adding alpha-naphthol and potassium hydroxide to the Voges-Proskauer broth, which is a glucose-phosphate broth that has been inoculated with bacteria. A cherry red color indicates a positive result, while a yellow-brown color indicates a negative result.

Glucose phosphate broth is used to perform methyl red (MR) test and Voges–Proskauer test (VP).

Acetoin dehydrogenase (EC 2.3.1.190, acetoin dehydrogenase complex, acetoin dehydrogenase enzyme system, AoDH ES) is an enzyme with systematic name acetyl-CoA:acetoin O-acetyltransferase. This enzyme catalyses the following chemical reaction

Diacetyl reductase ((R)-acetoin forming) (EC 1.1.1.303, (R)-acetoin dehydrogenase) is an enzyme with systematic name (R)-acetoin:NAD+ oxidoreductase. This enzyme catalyses the following chemical reaction

<span class="mw-page-title-main">Diacetyl reductase ((S)-acetoin forming)</span>

Diacetyl reductase ((S)-acetoin forming) (EC 1.1.1.304, (S)-acetoin dehydrogenase) is an enzyme with systematic name (S)-acetoin:NAD+ oxidoreductase. This enzyme catalyses the following chemical reaction

<span class="mw-page-title-main">Acetylpropionyl</span> Chemical compound

Acetylpropionyl, also known as acetyl propionyl or 2,3-pentanedione, is an organic compound, specifically a diketone.

References

  1. ↑ Albert Gossauer: Struktur und Reaktivität der Biomoleküle, Verlag Helvetica Chimica Acta, Zürich, 2006, Seite 285, ISBN   978-3-906390-29-1.
  2. ↑ Xiao, Z.; Xu, P. (2007). "Acetoin metabolism in bacteria". Crit Rev Microbiol. 33 (2): 127–140. doi:10.1080/10408410701364604. PMID   17558661. S2CID   46151943.
  3. ↑ Oppermann, F.B.; Steinbuchel, A. (1994). "Identification and molecular characterization of the aco genes encoding the Pelobacter carbinolicus acetoin dehydrogenase enzyme system". J. Bacteriol. 176 (2): 469–485. doi:10.1128/jb.176.2.469-485.1994. PMC   205071 . PMID   8110297.
  4. ↑ Speckman, R.A.; Collins, E.B. (1982). "Specificity of the Westerfeld adaptation of the Voges-Proskauer test". Appl Environ Microbiol. 44 (1): 40–43. Bibcode:1982ApEnM..44...40S. doi:10.1128/aem.44.1.40-43.1982. PMC   241965 . PMID   6751225.
  5. ↑ Pavia et al., Introduction to Organic Laboratory Techniques, 4th ed., ISBN   978-0-495-28069-9
  6. ↑ "Sampling and Analytical Methods: Acetoin, Diacetyl, 1012". Archived from the original on 2018-06-04.
  7. ↑ "Allendale Columbia | STEM".
  8. ↑ "Evaluation of Natural Acetyl Methyl Carbinol|Flavorist". www.fks.com.
  9. ↑ Committee on the Review of the Health Effects of Electronic Nicotine Delivery Systems, National Academies of Sciences (2018). "Chapter 5: Toxicology of E-Cigarette Constituents". In Eaton, David L.; Kwan, Leslie Y.; Stratton, Kathleen (eds.). Public Health Consequences of E-Cigarettes. National Academies Press. p. 175. ISBN   9780309468343. PMID   29894118.
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