What named effect describes oxygen reducing fermentation, as observed by Pasteur?

The named effect describing oxygen reducing fermentation is the Pasteur effect. Pasteur observed that when yeast was exposed to air, its growth increased while its production of alcohol decreased. The finding connected oxygen availability with a shift in how cells obtain energy.

When oxygen is scarce, yeast relies more heavily on fermentation, converting sugar into ethanol and carbon dioxide. When oxygen is available, it can use aerobic respiration, which extracts more energy from each sugar molecule. Because respiration is more efficient, the yeast can grow with less sugar consumed through fermentation.

The effect is not the same as pasteurization, which is a heat-treatment process used to reduce harmful or spoilage microorganisms in liquids. It is also distinct from the Crabtree effect, in which some yeast continues fermenting even when oxygen is present and sugar is abundant. In medical contexts, the term can also describe oxygen-related suppression of glycolysis and lactate production.