How do yeast still work?

[mfischer2]

We all know that yeast tends to mutate after several (20, 30?) batches and you need to start fresh. So let's say I am a brewery, and I've reused my yeast 30 times. So now I go back to a slant and start over. Eventually my slant runs out and I call White Labs for more slants. But White Labs has to propigate the yeast somehow, there's not enough yeast at White Labs to give everyone 1st gen yeast. So, won't my brewery bet getting yeast from White Labs that is already on its, say, 15th generation? I mean, in nature yeast has undergone millions of generations already, so why do these extra 30 that the brewery does cause harm?

Is it the conditions (fairly high alcohol content and eventually running out of food) that cause the mutation? How do yeast companies propigate yeast without the mutation?

[bub]

I've often wondered this myself, I have come up with "Magic" and the fact that the White Brothers are so handsome that they don't cause mutation... cought cough.
Actually I think that the mutation is caused by "working" and the environment of that they are grown in is so sterile and perfect that mutation is significantly reduced.
BUB

[DrunkenIrish]

I'm more curious about what the White boys are doing with all of that spent yeast media. I mean, they have to grow up huge vats of these things, then let them settle out (maybe spin them down) and package them in a more concentrated form. What are they doing with all the media?