What is the Difference Between Pasteur Effect and Crabtree Effect

The key difference between Pasteur effect and Crabtree effect is that Pasteur effect is induced by lack of oxygen, whereas Crabtree effect is induced by excess glucose.

Pasteur effect is the effect of inhibiting oxygen in the fermentation process. Crabtree effect is the phenomenon in which yeast produces ethanol in aerobic conditions at high external glucose concentrations. These effects are closely related to each other, but the cause for the effect is different from each other, as stated above in the key difference section.

1. Overview and Key Difference
2. What is Pasteur Effect
3. What is Crabtree Effect
4. Similarities – Pasteur Effect and Crabtree Effect
5. Pasteur Effect vs Crabtree Effect in Tabular Form
6. Summary – Pasteur Effect vs Crabtree Effect

What is Pasteur Effect?

Pasteur effect is the effect of inhibiting oxygen in the fermentation process. This effect converts the process suddenly from anaerobic to aerobic. This was first introduced by Louis Pasteur in 1857. He showed that the aerating yeasted broth could cause yeast cell growth to increase, while conversely, fermentation rate decreases.

Pasteur Effect vs Crabtree Effect in Tabular Form

Figure 01: Portrait of Louis Pasteur in his Laboratory

Typically, yeast is a facultative anaerobe that is able to produce energy using two major metabolic pathways. When the oxygen concentration is low, they give ethanol and carbon dioxide from pyruvate in glycolysis. Here, the efficiency of energy produced is very low. At high oxygen concentration, pyruvate converts into acetyl Co-A and the energy efficiency become high. The Pasteur effect occurs only if glucose concentration is low and under the limited concentrations of nitrogen and other nutrients.

What is Crabtree Effect?

Crabtree effect is the phenomenon in which yeast produces ethanol in aerobic conditions at high external glucose concentrations. This concept was first introduced by the English biochemist Herbert Grace Crabtree. The usual process aerobically occurring in yeast is the production of biomass via the tricarboxylic acid cycle.

Pasteur Effect and Crabtree Effect - Side by Side Comparison

Figure 02: Ethanol Fermentation

Increasing the concentrations of glucose can cause an acceleration of the glycolysis process and produce appreciable amounts of ATP through substrate-level phosphorylation. Moreover, this effect causes the reduction of the need for oxidative phosphorylation that occurs through the TCA cycle (through the electron transport chain), decreasing the oxygen consumption. The Crabtree effect has evolved as a competition mechanism around the time when the fruits fall from trees for the first time. Moreover, this effect works through the repression of respiration through the fermentation pathway, which depends on the substrate.

What are the Similarities Between Pasteur Effect and Crabtree Effect?

Both effects cause the initiation of fermentation.
These effects are closely related to each other.

What is the Difference Between Pasteur Effect and Crabtree Effect?

Pasteur effect is the effect of inhibiting oxygen on the fermentation process. Crabtree effect is the phenomenon in which the yeast produces ethanol in aerobic conditions at high external glucose concentrations. These effects are closely related to each other, but the cause for the effect is different from each other. The key difference between Pasteur effect and Crabtree effect is that the Pasteur effect is induced by lack of oxygen, whereas the Crabtree effect is induced by excess glucose.

The below infographic lists the differences between Pasteur effect and Crabtree effect in tabular form for side by side comparison

Summary – Pasteur Effect vs Crabtree Effect

The Pasteur effect is the effect of inhibiting oxygen in the fermentation process. Crabtree effect is the phenomenon in which the yeast produces ethanol in aerobic conditions at high external glucose concentrations. These effects are closely related to each other, but the cause for the effect is different from each other. The key difference between Pasteur effect and Crabtree effect is that the Pasteur effect is induced by lack of oxygen, whereas the Crabtree effect is induced by excess glucose.