fermentation

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The foaming surface of a fermenting substance due to outgassing

The meaning of the term fermentation has changed with the advancement of science.

Older definition

The term fermentation was originally applied to recognizable changes in biotic substances - changes in mass, associated, for example, with bulging, gas formation, heating and decomposition, but without the development of a putrid smell. The influence of air was not taken into account, even when oxygen was discovered. Accordingly, the processes involved in converting must into wine , wort into beer, and wine into vinegar were referred to as fermentation . This is still common in technology today.

Research history

The German doctor and chemist Johann Joachim Becher taught the difference between putrefaction and fermentation as early as 1650. He also distinguished alcoholic (“spiritual”) from acidic fermentation (associated with the formation of acetic and lactic acid). Around 1815, the chemical equation of alcoholic fermentation was established by Joseph Louis Gay-Lussac . Eilhard Mitscherlich suspected biological catalysts (ferments) that only come into contact with sugar and do not change themselves.

Based on Mitscherlich's ideas, Charles Cagniard de la Tour was able to detect living organisms through microscopic examinations. Theodor Schwann found that a meat extract remains undecomposed for a long time after being heated to 100 ° C in air-tight containers. He repeated these attempts with a sugar solution and was able to avoid fermentation in this case too. Friedrich Traugott Kützing found out that the fermentation of sugary liquids, combined with the formation of ethanol and carbon dioxide ( alcoholic fermentation ), is a biotic process and brewer's yeast consists of microorganisms .

Louis Pasteur researched lactic acid fermentation in 1857 and butyric acid fermentation in 1861 . He discovered that the microorganisms in butyric acid fermentation can live, metabolize and grow without oxygen and that oxygen has an inhibiting effect on them, which was surprising at the time. In other types of fermentation, too, it has been proven that fermentation organisms can live without oxygen.

The finding that the fermentations examined (alcoholic fermentation, lactic acid fermentation and butyric acid fermentation) take place without oxygen was initially assumed to be applicable for all types of fermentation. However, it was later realized that not all fermentations take place without the inclusion of oxygen, for example acetic acid fermentation . For this reason, new, somewhat different definitions of fermentation have been formulated, but all of which exclude oxygen (O 2 ) as an electron acceptor.

Newer definition

The new definition for fermentation is: "Microbial degradation of organic substances without the involvement of external electron acceptors such as oxygen (O 2 ) for the purpose of generating energy."

Organic substances can generally be broken down under anaerobic or aerobic conditions. For example, in what is known as acetic acid fermentation, oxygen is consumed. However, this does not correspond to the new definition. Acetic acid fermentation is therefore not fermentation in the new ( scientific ) sense.

An additional uncertainty caused by the fact that fermentation in English as fermentation is referred to. In German, however, the term fermentation is used in at least three different meanings:

  • Fermentation in the more recent meaning: biotic energy metabolism without the inclusion of oxygen.
  • Changes in biotic raw materials, initiated for the manufacture of certain products, for example fermentation of tobacco leaves in the manufacture of smoking tobacco and fermentation of the contents of cocoa pods (including their seeds) in the course of the manufacture of cocoa powder and chocolate . Oxygen is not excluded or only partially excluded.
  • In biotechnology, the controlled production of biotic metabolic products, with or without the inclusion of oxygen.

Types of fermentation

meaning

Biological importance

Compared to respiration , only a small amount of energy is gained during fermentation, since instead of the citric acid cycle and the subsequent respiratory chain, only the substrate chain phosphorylation is used. Fermentation, however, is a way to rapidly form adenosine triphosphate (ATP) through substrate chain phosphorylation . This is also advantageous for anaerobically growing organisms, since they do not depend on the external electron acceptor oxygen.

In some cases, the habitats of more highly developed, aerobic organisms are also poor in oxygen. Coelaceans and other marine vertebrates ferment to meet their energy needs, as they live in depths where the concentration of dissolved oxygen is low. Also squid relate some of their energy from the fermentation of pyruvate and causes both octopine .

Organisms that carry out fermentation are also called (primary) fermenters. Some microorganisms, on the other hand, are so-called secondary fermenters : They take up the fermentation products of primary fermenters and ferment them further to carbon dioxide (CO 2 ), acetate or hydrogen (H 2 ).

Technical importance

Fermentations are used in a variety of ways to produce, refine and preserve food and feed (especially alcoholic fermentation and lactic acid fermentation).

See also

literature

  • Katharina Munk (Ed.): Pocket textbook Biology: Microbiology. Thieme, Stuttgart 2008, ISBN 978-3-13-144861-3 .
  • Reinhard Renneberg: Biotechnology for beginners. 2nd Edition. Elsevier Spektrum Akademischer Verlag, Munich 2007, ISBN 3-827-41847-X .

Web links

Commons : Fermentation  - collection of pictures, videos and audio files

Individual evidence

  1. ^ Otto Westphal , Theodor Wieland , Heinrich Huebschmann: life regulator. Of hormones, vitamins, ferments and other active ingredients. Societäts-Verlag, Frankfurt am Main 1941 (= Frankfurter Bücher. Research and Life. Volume 1), p. 58 f.
  2. ^ Comptes rendus de l'Academie des Sciences, 4 , 903 (1837).
  3. ^ Charles Cagniard-Latour: Mémoire sur la fermentation vineuse. In: Annales de chimie et de physique . Vol. 68, 1838, pp. 206-222.
  4. ↑ Pogg. Ann. d. Ph., 41 , 184 (1837).
  5. ↑ Theodor Schwann: Preliminary communication, concerning experiments on fermentation and putrefaction. In: Annals of Physics and Chemistry . Vol. 41, 1837, pp. 184-193.
  6. ↑ Kützing, FT (1837): Microscopic investigations on yeast and mother vinegar, along with several other associated vegetable structures . In: Journ. Practical Chem . 11, pp. 385-409.
  7. ↑ Louis Pasteur: Mémoire sur la fermentation appelée lactique. (Extrait des l'auteur). In: Comptes rendus de l'Académie des Sciences . Vol. 45, 1857, pp. 913-916.
  8. ↑ Louis Pasteur: Animalcules infusoires vivant sans gaz oxygène libre et déterminant des fermentation. In: Comptes rendus de l'Académie des Sciences. Vol. 52, 1861, pp. 344-347.
  9. ↑ Franz Lafar : The acetic acid fermentation . In: Franz Lafar (Ed.): Handbuch der Technischen Mykologie , Vol. V, Kap. 19, Gustav Fischer, Jena 1913.
  10. ↑ Alfred Pühler, Manfred Regitz and Rolf D. Schmid: Römpp Compact Lexicon Biochemistry and Molecular Biology . Thieme, Stuttgart 2000; ISBN 3-13-116681-9 ; P. 200.
  11. ↑ Katharina Munk (ed.): Pocket textbook Biology: Microbiology . Thieme Verlag Stuttgart, New York 2008, ISBN 978-3-13-144861-3 , p. 376.