Reusing Yeast

[Tarpon87]

I have just begun to overbuild starters, split them, saving half and pitching half. Is there a limit to how many times I can keep doing this with the same yeast before I start getting some unwanted mutations? Right now I just have 1272, but I plan on doing this with any yeast I buy in the future.

Also I have the dregs from 6 bottles of Bell's Oberon, I assume I could just do the same thing with this. Being bottle dregs, does it change anything as opposed to building from a yeast pack?

Thanks

 

[flars]

I've never had a problem using the overbuild for a new starter. To me using the overbuild to make a new starter is like using a new pack of yeast. The overbuild yeast harvested from a starter has never undergone the stress of fermenting out a beer.

 

[Dcpcooks]

You should be good to about 5-7 generations assuming above average sanitation and storage procedures. Your mileage may vary.

Bottle dregs are a different story as you have no idea how many cycles the yeast went through at the brewery before you got it. It could have been the 10th generation and may have mutated or drifted a bit. There is no way to know how old the yeast is.

The benefit of overbuilding a pack of yeast in a starter is lack of stress from fermentation. Your not really stressing a starter with 1.035-1.040 wort your building yeast.

 

[helibrewer]

There are two main concerns with yeast: Vitality and Viability. Viability is the amount of live yeast you have, vitality is whether those live yeast are eager teenagers, or old retirees

The other side issue, is mutation through life cycles. Any growth phase is counting toward life cycles so even starters contribute to life cycle aging. Starter-only growth should do a good job of preserving viability (with proper nutrition/conditions) and vitality (due to low life cycle count).

 

[jakwi]

You should be good to about 5-7 generations assuming above average sanitation and storage procedures. Your mileage may vary.

Bottle dregs are a different story as you have no idea how many cycles the yeast went through at the brewery before you got it. It could have been the 10th generation and may have mutated or drifted a bit. There is no way to know how old the yeast is.

The benefit of overbuilding a pack of yeast in a starter is lack of stress from fermentation. Your not really stressing a starter with 1.035-1.040 wort your building yeast.

I never really understood this, although I've read it many places. To me if you have good sanitation, and oxygenation in your starters you should be able to rebuild indefinitely. I imagine that is how the yeast producers are able to do it. The only real difference between them and us is that they, more than likely, have better sanitation, and a way to verify isolated strains are not contaminated.

Maybe I'm wrong, but I've been using the product of a starter split for a couple of years now. About every 6 months I make sure all of my stored yeast is dumped into a fresh starter and rebuilt from there. So by that metric I'm only 4 generations in or so.