This MedLibrary.org supplementary page on Pasteur effect is provided directly from the open source Wikipedia as a service to our readers. Please see the note below on authorship of this content, as well as the Wikipedia usage guidelines. To search for other content from our encyclopedia supplement, please use the form below:
Related Sponsors
The Pasteur effect is an inhibiting effect of oxygen on the fermentation process.
Contents |
Discovery
The effect was discovered in 1857 by Louis Pasteur, who showed that aerating yeasted broth causes yeast cell growth to increase, while conversely, fermentation rate decreases.
Explanation
The effect can be easily explained, as the yeast being facultative anaerobes can produce energy using two different metabolic pathways. While the oxygen concentration is low, the product of glycolysis, (pyruvate), is turned into ethanol and carbon dioxide, and the energy production efficiency is low (2 moles of ATP per mole of glucose). If the oxygen concentration grows, pyruvate is converted to acetyl CoA that can be used in the Krebs Cycle, which increases the efficiency to 16 moles of ATP per 1 moles of glucose.
Under anaerobic conditions, the rate of glucose metabolism is faster, but the amount of ATP produced (as already mentioned) is smaller. When exposed to aerobic conditions, the rate of glycolysis slows, because the increase in ATP production acts as an allosteric inhibitor for the pathway.
So, from the standpoint of ATP production, it is advantageous for yeast to undergo the Krebs Cycle in the presence of oxygen, as more ATP is produced with less glucose. The rapid production of ethanol (and rapid depletion of sugar), on the other hand, probably confers an advantage in the wild.
Practical implications
All the processes used in alcohol production are kept in anaerobic conditions, while breeding yeast for biomass is done in aerobic conditions, the broth being aerated.
Bibliography
- Krebs, Hans. « The Pasteur effect and the relations between respiration and fermentation. » Essays in Biochemistry, 1972, 8, 1-34
See also
 |
This biochemistry article is a stub. You can help Wikipedia by expanding it. |
 |
This beer- or brewery-related article is a stub. You can help Wikipedia by expanding it. |
Wikipedia content modification information:
- This page was last modified on 23 October 2008, at 18:31.
Wikipedia Authorship and Review
Wikipedia content provided here is not reviewed directly by MedLibrary.org. Wikipedia content is authored by an open community of volunteers and is not produced by or in any way affiliated with MedLibrary.org.
Wikipedia Usage Guidelines
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article on "Pasteur effect".
The URL for this specific entry is:
All Wikipedia text is available under the terms of the GNU Free Documentation License. (See Copyrights for details). Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc.