What could be done to force yeast to switch to anaerobic fermentation? Think rea

Question

What could be done to force yeast to switch to anaerobic fermentation? Think realistically how this might be accomplished. Baker's Yeast is also known as Brewer's Yeast because it is used to ferment sugar sources and produce alcohol in an environment void of oxygen. Because the production of alcohol utilizes anaerobic fermentation to ferment sugars from grapes, the level of sugars present drops as the sugars are broken down until anaerobic fermentation ceases completely, despite the fact that sufficient levels of sugar may still remain. Suggest an explanation for why this might happen 1. 2.

Explanation / Answer

1. Yeast can switch from aerobic to anaerobic pathway based on the availability of oxygen. When oxygen is around they can use oxygen as electron acceptor at the end of electron transport chain and make more ATPs whereas to keep metabolizing and to stay alive they switch to anaerobic pathway. To force the yeast to switch to anaerobic respiration, we can put a cap/cotton plug on test tube/funnel after adding yeast to the sugar solution.

2. Alcohol fermentation by yeast produces the ethanol found in alcoholic drinks like beer and wine. In the process of NAD+ regeneration after glycolysis, ethanol and carbon dioxide are produced as byproducts. However ethanol is toxic to yeast in large quantities. As the yeast continues to metabolize sugar, the alcohol level increases and reach toxic levels for yeast, at that point ethanol inhibits the growth of yeast. Thus if there is no yeast, there is no question of anaerobic respiration though the sugar in the medium may still remain. Ethanol tolerance of yeast ranges from about 5 percent to 21 percent, depending on the yeast strain.

3. Yeasts are capable of using some, but not all, sugars as a food source. the production of carbon dioxide gas will be measured to indicate the rate of respiration. The rate of respiration will be overall faster in sucrose medium because it contains more energy than glucose even though it must be broken down before use. Simple sugars are broken down very quickly and are an immediate source for energy. .Maltose is the best for yeast metabolism. Remember, maltose is made of two glucose molecules. Glucose (aka dextrose) is a close second. Fructose is in third place. Sugar substitutes provide less energy than carbohydrates (natural sugar), causing organisms that use sugar substitutes to move slower, more “sluggish.”

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