2,3-Butanediol fermentation is
anaerobic Anaerobic means "living, active, occurring, or existing in the absence of free oxygen", as opposed to aerobic which means "living, active, or occurring only in the presence of oxygen." Anaerobic may also refer to: * Anaerobic adhesive, a bonding a ...
fermentation of
glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...
2,3-butanediol 2,3-Butanediol is the organic compound with the formula (CH3CHOH)2. It is classified as a ''vic''-diol ( glycol). It exists as three stereoisomers, a chiral pair and the meso isomer. All are colorless liquids. Applications include precursors ...
as one of the end products. The overall stoichiometry of the reaction is :2 pyruvate +
NADH Nicotinamide adenine dinucleotide (NAD) is a coenzyme central to metabolism. Found in all living cells, NAD is called a dinucleotide because it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an aden ...
--> 2 CO2 + 2,3-butanediol. Butanediol fermentation is typical for the facultative anaerobes ''
Klebsiella ''Klebsiella'' is a genus of Gram-negative, oxidase-negative, rod-shaped bacteria with a prominent polysaccharide-based capsule. ''Klebsiella'' species are found everywhere in nature. This is thought to be due to distinct sublineages developi ...
'' and ''
Enterobacter ''Enterobacter'' is a genus of common Gram-negative, facultatively anaerobic, rod-shaped, non-spore-forming bacteria of the family Enterobacteriaceae. It is the type genus of the order Enterobacterales. Several strains of these bacteria are ...
'' and is tested for using the Voges–Proskauer (VP) test. There are other alternative strains that can be used, talked about in details in the Alternative Bacteria Strains section below. The metabolic function of 2,3-butanediol is not known, although some have speculated that it was an evolutionary advantage for these microorganisms to produce a neutral product that's less inhibitory than other partial oxidation products and doesn't reduce the pH as much as mixed acids. There are many important industrial applications that butanediol can be used for, including antifreeze, food additives, antiseptic, and pharmaceuticals. It also is produced naturally in various places of the environment.

Comparison with mixed acid fermentation

2,3-butanediol fermentation produces smaller amounts of acid than mixed acid fermentation, and butanediol,
ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...
, CO2 and H2 are the end products. While equal amounts of CO2 and H2 are created during mixed acid fermentation, butanediol fermentation produces more than twice the amount of CO2 because the gases are not produced only by formate hydrogen lyase like they are in the mixed acid fermentation 2,3 Butanediol is produced at varying levels in aerated fermentations as long as the dissolved oxygen level is limiting (i.e., the culture is trying to consume more oxygen than is available). The degree of oxygen limitation dictates the ratios of 2,3-butanediol to by-products produced

Butanediol properties

Butanediol has various properties that help contribute to its many industrial applications and effect how it is processed during manufacturing. Butanediol is an odorless and colorless liquid. It has a high boiling point, 180-184 °C that can impact downstream processes and cause problems while recovering the fermented slurry. It also has a low freezing point, which allows it to be used for industrial applications.

Industrial applications

2,3-butanediol has a variety of industrial applications and products it can produce. The levo isomer of butanediol has a low freezing point of -60 °C, which allows it to work as an antifreeze agent. Through catalytic
dehydrogenation In chemistry, dehydrogenation is a chemical reaction that involves the removal of hydrogen, usually from an organic molecule. It is the reverse of hydrogenation. Dehydrogenation is important, both as a useful reaction and a serious problem. At ...
, butanediol can form diacetyl.
Diacetyl Diacetyl (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). Diacet ...
is a food additive that can be used to add flavor. 0.1% butanediol will kill most pathogenic bacteria due to its antiseptic properties. Through esterification, forms of precursors of polyurethane foams are produced. These can be used in various applications, including in pharmaceuticals, cosmetics, lotions, ointments, and antiperspirants. Butanediol itself even has applications in the pharmaceutical industry as a drug carrier.

Natural occurrences

2,3-butanediol can be produced naturally in various places in the environment. A few places are sweet corn, fermented soybean curds, whole and ground grains, rotten mussels, and during the fermentation of fruits and grains.

Alternative bacteria strains

Using mesophilic bacteria requires the fermentation process to occur below 40 °C, which can cause bacterial contamination due to the low temperature. On the industrial scale, this requires sterilization steps which means a special facility must be built, more employees are needed to run this extra step, and more energy is consumed at the plant. A novel aerobic '' Geobacillus'' strain XT15 has been shown to produce 2,3-butanediol at a temperature between 45 and 55 °C. This higher temperature will avoid the risk of contamination because microorganisms that live in normal environments cannot reproduce above 45 °C. The ''Geobacillus'' strain XT15 is
thermophilic A thermophile is an organism—a type of extremophile—that thrives at relatively high temperatures, between . Many thermophiles are archaea, though they can be bacteria or fungi. Thermophilic eubacteria are suggested to have been among the earl ...
, which allows it to be able to operate fermentation at this higher temperature. Sterilization would not be necessary using this alternative strain making the manufacturing process more efficient and cost-effective.


Further reading


External links

* {{DEFAULTSORT:Butanediol Fermentation Fermentation