What is "fermentation"

Fermentation \Fer`men*ta"tion\ (f[~e]r`m[e^]n*t[=a]"sh[u^]n), n.

1. The process of undergoing an effervescent change, as by the action of yeast; in a wider sense (Physiol. Chem.), the transformation of an organic substance into new compounds by the action of a ferment[1], whether in the form of living organisms or enzymes. It differs in kind according to the nature of the ferment which causes it.

   Note: In industrial microbiology fermentation usually refers to the production of chemical substances by use of microorganisms.

2. A state of agitation or excitement, as of the intellect or the feelings. It puts the soul to fermentation and activity. --Jer. Taylor. A univesal fermentation of human thought and faith. --C. Kingsley. Acetous fermentation or Acetic fermentation, a form of oxidation in which alcohol is converted into vinegar or acetic acid by the agency of a specific fungus ( Mycoderma aceti) or series of enzymes. The process involves two distinct reactions, in which the oxygen of the air is essential. An intermediate product, acetaldehyde, is formed in the first process.

   1. C2H6O + O [rarr] H2O + C2H4O

      Note: Alcohol. Water. Acetaldehyde.

   2. C2H4O + O [rarr] C2H4O2

      Note: Acetaldehyde. Acetic acid.

      Alcoholic fermentation, the fermentation which saccharine bodies undergo when brought in contact with the yeast plant or Torula. The sugar is converted, either directly or indirectly, into alcohol and carbonic acid, the rate of action being dependent on the rapidity with which the Torul[ae] develop.

      Ammoniacal fermentation, the conversion of the urea of the urine into ammonium carbonate, through the growth of the special urea ferment. CON2H4 + 2H2O = (NH4)2CO3

      Note: Urea. Water. Ammonium carbonate.

      Note: Whenever urine is exposed to the air in open vessels for several days it undergoes this alkaline fermentation.

      Butyric fermentation, the decomposition of various forms of organic matter, through the agency of a peculiar worm-shaped vibrio, with formation of more or less butyric acid. It is one of the many forms of fermentation that collectively constitute putrefaction. See Lactic fermentation.

      enzymatic fermentation or Fermentation by an unorganized ferment. Fermentations of this class are purely chemical reactions, in which the enzyme acts as a simple catalytic agent. Of this nature are the decomposition or inversion of cane sugar into levulose and dextrose by boiling with dilute acids, the conversion of starch into dextrin and sugar by similar treatment, the conversion of starch into like products by the action of diastase of malt or ptyalin of saliva, the conversion of albuminous food into peptones and other like products by the action of pepsin-hydrochloric acid of the gastric juice or by the ferment of the pancreatic juice.

      Fermentation theory of disease (Biol. & Med.), the theory that most if not all, infectious or zymotic disease are caused by the introduction into the organism of the living germs of ferments, or ferments already developed (organized ferments), by which processes of fermentation are set up injurious to health. See Germ theory.

      Glycerin fermentation, the fermentation which occurs on mixing a dilute solution of glycerin with a peculiar species of schizomycetes and some carbonate of lime, and other matter favorable to the growth of the plant, the glycerin being changed into butyric acid, caproic acid, butyl, and ethyl alcohol. With another form of bacterium ( Bacillus subtilis) ethyl alcohol and butyric acid are mainly formed.

      Lactic fermentation, the transformation of milk sugar or other saccharine body into lactic acid, as in the souring of milk, through the agency of a special bacterium ( Bacterium lactis of Lister). In this change the milk sugar, before assuming the form of lactic acid, presumably passes through the stage of glucose. C12H22O11.H2O
      --> 4C3H6O3

      Note: Hydrated milk sugar. Lactic acid.

      Note: In the lactic fermentation of dextrose or glucose, the lactic acid which is formed is very prone to undergo butyric fermentation after the manner indicated in the following equation: 2C3H6O3 (lactic acid)
      --> C4H8O2 (butyric acid) + 2CO2 (carbonic acid) + 2H2 (hydrogen gas).

      Putrefactive fermentation. See Putrefaction.

late 14c., in alchemy, with a broad sense; modern scientific sense is from c.1600; from Late Latin fermentationem (nominative fermentatio), noun of action from past participle stem of Latin fermentare "to ferment" (see ferment (v.)). Figurative use attested from 1650s.

n. 1 (context biochemistry English) Any of many anaerobic biochemical reactions in which an enzyme (or several enzymes produced by a microorganism) catalyses the conversion of one substance into another; especially the conversion (using yeast) of sugars to alcohol or acetic acid with the evolution of carbon dioxide 2 A state of agitation or excitement; a ferment.

1. n. a process in which an agent causes an organic substance to break down into simpler substances; especially, the anaerobic breakdown of sugar into alcohol [syn: zymosis, zymolysis, fermenting, ferment]

2. a state of agitation or turbulent change or development; "the political ferment produced a new leadership"; "social unrest" [syn: agitation, ferment, unrest]

3. a chemical phenomenon in which an organic molecule splits into simpler substances [syn: ferment]

Fermentation is a metabolic process whereby electrons released from nutrients are ultimately transferred to molecules obtained from the breakdown of those same nutrients.

Fermentation may also refer to:

• Ethanol fermentation, the production of ethanol for use in food, alcoholic beverage, fuel and industry
  • Fermentation in food processing, the process of converting sugar to carbon dioxide and alcohol with yeast
  • Fermentation in winemaking, the process of fermentation used in wine-making
• Lactic acid fermentation, the biological process by which sugars such as glucose, fructose, and sucrose, are converted into cellular energy and the metabolic byproduct lactate
• Industrial fermentation, the breakdown and re-assembly of biochemicals for industry, often in aerobic growth conditions
• Fermentative hydrogen production, the fermentative conversion of organic substrate to biohydrogen manifested by a diverse group of bacteria

Fermentation is a metabolic process that converts sugar to acids, gases, or alcohol. It occurs in yeast and bacteria, and also in oxygen-starved muscle cells, as in the case of lactic acid fermentation. Fermentation is also used more broadly to refer to the bulk growth of microorganisms on a growth medium, often with the goal of producing a specific chemical product. French microbiologist Louis Pasteur is often remembered for his insights into fermentation and its microbial causes. The science of fermentation is known as zymology.

Fermentation takes place when the electron transport chain is unusable (often due to lack of a final electron receptor, such as oxygen), and becomes the cell’s primary means of ATP (energy) production. It turns NADH and pyruvate produced in glycolysis into NAD and an organic molecule (which varies depending on the type of fermentation; see examples below). In the presence of O, NADH and pyruvate are used to generate ATP in respiration. This is called oxidative phosphorylation, and it generates much more ATP than glycolysis alone. For that reason, cells generally benefit from avoiding fermentation when oxygen is available, the exception being obligate anaerobes which cannot tolerate oxygen.

The first step, glycolysis, is common to all fermentation pathways:

Pyruvate is CHCOCOO. P is inorganic phosphate. Two ADP molecules and two P are converted to two ATP and two water molecules via substrate-level phosphorylation. Two molecules of NAD are also reduced to NADH.

In oxidative phosphorylation the energy for ATP formation is derived from an electrochemical proton gradient generated across the inner mitochondrial membrane (or, in the case of bacteria, the plasma membrane) via the electron transport chain. Glycolysis has substrate-level phosphorylation (ATP generated directly at the point of reaction).

Humans have used fermentation to produce food and beverages since the Neolithic age. For example, fermentation is used for preservation in a process that produces lactic acid as found in such sour foods as pickled cucumbers, kimchi and yogurt (see fermentation in food processing), as well as for producing alcoholic beverages such as wine (see fermentation in winemaking) and beer. Fermentation can even occur within the stomachs of animals, such as humans.