Acetoin

Acetoin
Other names

3-Hydroxybutanone
Acetyl methyl carbinol
Identifiers
CAS number 513-86-0 Y
ChemSpider 21105851 Y
UNII BG4D34CO2H Y
KEGG C01769 Y
ChEBI CHEBI:15688 Y
Jmol-3D images Image 1
Properties
Molecular formula C4H8O2
Molar mass 88.11 g mol−1
Density 1.012 g/cm³
Melting point

15 °C, 288 K, 59 °F
Boiling point

148 °C, 421 K, 298 °F
Hazards
MSDS MSDS
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Acetoin , also known as 3-hydroxybutanone or acetyl methyl carbinol, with the molecular formula is C4H8O2. It is a colorless or pale yellow to green yellow liquid with a pleasant buttery odor.

Contents

Production in bacteria

Acetoin is a neutral, four carbon molecule used as an external energy store by a number of fermentive bacteria. Acetoin 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 acetate and citrate. Once superior carbon sources are exhausted, and the culture enters stationary phase, acetoin can be utilised in order to maintain the culture density.[1] 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.[2] 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.[3]

In food products

Acetoin, along with diacetyl, is one of the compounds giving butter its characteristic flavor. Because of this, manufacturers of partially hydrogenated oils typically add acetoin and diacetyl (along with beta carotene for the yellow color) to the final product, which would otherwise be tasteless.[4]

Acetoin is used as a food flavoring (in baked goods) and a fragrance. It can be found in apples, butter, yogurt, asparagus, black currants, blackberry, wheat, broccoli, brussels sprouts, cantaloupe.

Cigarette additive

In a 1994 report released by five top cigarette companies, acetoin was listed as one of the 599 additives to cigarettes. [5]

References

  1. ^ Xiao, Z. and Xu, P. (2007). "Acetoin metabolism in bacteria". Crit Rev Microbiol. 33 (2): 127–140. doi:10.1080/10408410701364604. PMID 17558661. 
  2. ^ Oppermann, F.B. and 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. PMC 205071. PMID 8110297. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=205071. 
  3. ^ Speckman, R.A. and Collins, E.B. (1982). "Specificity of the Westerfeld adaptation of the Voges-Proskauer test". Appl Environ Microbiol. 44 (1): 40–43. PMC 241965. PMID 6751225. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=241965. 
  4. ^ Pavia et al., Introduction to Organic Laboratory Techniques, 4th ed., ISBN 978-0-495-28069-9
  5. ^ "What's in a cigarette?". http://quitsmoking.about.com/cs/nicotineinhaler/a/cigingredients.htm. Retrieved 2006-05-31.