Yeast starter/stir plate theory confusion

[AnOldUR]

In fact, because the solution at this point will contain greater than 0.4% glucose, aerobic metabolism will initially be inhibited. Only after the glucose content of the solution has been reduced below 0.4% will the catabolic repression of the Crabtree Effect be removed. At that point, if there is still oxygen left in solution, then the yeast WILL employ aerobic respiration and will reproduce quite efficiently until the oxygen is used up.

Will beginning with a lower initial gravity of the starter wort have any advantage by shortening the time to reach catabolic repression? What would be optimal starting gravity if continuously aerating with an aggressive whirlpool were employed?

 

[silverbrewer]

I have read through all this and have an additional question.

Why can't those with oxygen equipment, squirt a tiny constant stream of oxygen into the neck of the flask to ensure that there is always plenty of oxygen inside the flask while it is being stirred?

 

[Droot]

I could add more o2, but I don't think I have to. I have a 1.2 liter starter going right now on the stir plate. Its been less than 24 hours since I pitched the yeast. Its at high krausen. It was a washed Wyeast 1272 american ale II.



Twice as fast, half the wort needed.

 

[msheraw]

1. If you go by the yeast life cycle you NEED to aerate the wort prior to pitching in a starter. I have noticed a significantly faster growth rate in the yeast and fermentation by just using a aquarium pump with a HEPA filter on it. Run it in the wort for about 10-15 minutes and then pitch. Usally even a slower liquid yeast takes off within a few hours.

2. I strongly believe that the oxygen does not migrate down the neck of the flask in to the wort, whether or not there is a vortex. I tried sticking a long butane lighter that you would use for a grill down in the neck and it is extinguished even before it passes the lip of the neck.