Microbial metabolism: Pasteur and Metabolism

» Rock - Pasteur and Metabolism

In 1861, Louis Pasteur observed that when yeast grow in a sugar and protein medium completely free of air, they ferment vigorously, and for every gram of yeast that forms, 60-80 grams of sugar disappear. If the experiment is carried out in the presence of air, for one gram of yeast that forms, only 4-10 grams of sugar are removed. The yeast again ferment if transferred to a sugar-containing medium absent of air. When the experiment is repeated with a protein medium, the yeast grow only in the presence of oxygen. Pasteur concluded that the yeast can take oxygen from air, and in the absence of air, the yeast take oxygen from the sugar.

Pasteur applied quantitative methods to his studies of fermentation and was the first to report on organisms that could live and reproduce in the absence of oxygen. His conclusion was, however, incorrect. These different behaviors of yeast are known today as the Pasteur effect.

Please explain the three yeast behaviors based on modern conepts of microbial metabolism.

What was incorrect about Pasteur's conclusion?

Thanks,
Rocco Pizza

-- posted by Rock