Question

When using yeast to produce wine, it is best to start with a culture of yeast that is consuming a lot of glucose, in the presence of oxygen. The oxygen supply is then discontinued and the culture becomes anaerobic. Ethanol production follows. Why is it important for the yeast to be consuming high levels of glucose when the oxygen is terminated? Explain your answer. After oxygen is discontinued, will glucose consumption increase or decrease?

Answer 1

It is important for the consumption of glucose to be more in yeast at start in aerobic condition because it shows that the yeast has predisposition for glycolysis , and less on aerobic pathway. Because of which less ATP are produced per glucose molecule and glucose is used more for the purpose. This shows that some sort of fermentation reaction is already also taking place or the glycolysis is prefered more than moving on to aerobic TCA cycle in yeast.

After starting anaerobic condition , the quantity of glucose increase as, now the yeast is totally dependent on fermentative pathway rather than opting for any TCA pathway, even in fractions. So, more glucose will be required for more ATP as efficiency of fermentation is less.