Crabtree effect

Crabtree effect ( by the English biochemist Herbert Grace Crabtree, and " glucose effect") describes the catabolism of the baker's yeast (Saccharomyces cerevisiae) the effect that in the presence of higher concentrations of glucose and in the presence of oxygen, ie under aerobic conditions, ethanol is formed.

When the glucose concentration exceeds a value of about 100 mg / l, uses this effect. The reason for this is that glucose represses the transcription of the respiratory genes. The pyruvate is not - as is usual under aerobic conditions - oxidized via the citric acid cycle and electron transport chain, but reduced to ethanol ( fermented ). For the following reasons the Crabtree effect is of economic importance:

Baker's yeast is as a blowing agent for the production of bakery products of great economic importance. Under the anaerobic conditions of fermentation converts various sugars (glucose, sucrose, fructose, maltose ) by by way of glycolysis into ethanol and carbon dioxide. In the presence of oxygen is normally different sugar are respired to carbon dioxide and water, the energy and hence the cell output increase by a multiple.

However, ethanol is formed under the conditions of the Crabtree effect, even under aerobic conditions, it results in the production of baker's yeast in a dramatic reduction in growth rate.