Why do yeast need oxygen?

[CaptainSwiller]

I have read that it is necessary to aerate your wort. However, from what I understand about the biochemical pathways of yeast, they need to perform anaerobic glycolysis to create ethanol and CO2. What is the explanation for this? I'm not looking for an answer that flies in the face of traditional brewing and sparks a revolution . The answer to this question isn't going to have any impact on how I make beer, I am simply curious. Thanks!

EDIT: Upon further thought I think I figured it out. Do the yeast need oxygen for a period of rapid growth? Then after the cells have multiplied and the oxygen is used up, they can begin to create ethanol through anaerobic glycolysis? Is this correct?

 

[Laughing_Gnome_Invisible]

Everything needs something. For yeast, it's oxygen.....For me, it's bear/aardvark porn.

Somene will be along in a moment with a proper answer. Great first ever post!!

 

[ChshreCat]

Yes, the yeast need O2 when they multiply. You give them a good dose of O2 at the start so they can build up a good cell count in your wort to do an good job when they go to their anaerobic stage and start munching up the sugars. That's what happens in the lag time between pitching and the start of fermentation.

 

[Yooper]

You're correct- fermentation is an anaerobic process. But, the yeast must reproduce first, which is an aerobic process.

 

[beersydoesit]

There is a great Basic Brewing Radio podcast on the life cycle of yeast.
I gather they store the stuff for reproduction.

The guy that knows is here.

Basic Brewing™ : Home Brewing Beer Podcast and DVD - Basic Brewing Radio™ 2007
Look for April 5, 2007
Regards