The Pasteur Effect
In 1861 Louis Pasteur observed that yeast, a facultativeanaerobe, could grow in a sugar and protein broth without air, i.e.Oxygen. For every gram of yeast in a culture, 60-80 grams of sugardisappeared from the broth. When the yeasts are cultured with air4-10 grams of sugar are consumed for every gram of yeast added tothe culture. When the yeasts were cultured only on protein broth,only yeast culture with air grew. Below is a table that summarizesthe conditions that allowed the yeast to grow.
1 g of yeast | Without oxygen | 60-80 g sugar |
1 g of yeast | With oxygen | 4-10 g of sugar |
1 g of yeast | With oxygen | Protein broth, no sugar |
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- How does this data demonstrate yeast are facultativeanaerobes?
- Is the ratio of sugar required without oxygen compared to thesugar required with oxygen like the ratio of ATP produced withfermentation and with aerobic respiration?
- How did the yeast without sugar grow?
- Why did the yeast with only protein in the broth require oxygento grow?
- Explain the Pasteur Effect.
