Ensure my yeast strategy is good here...

[DVCNick]

Now that I've done my first (I think) successful yeast starter, I have the following idea to save money on yeast and use one pack of WLP001 for several batches.

Rather than harvest off the bottom of a batch, I'm thinking of doing starter split ups to keep it "cleaner" as follows:

1) Do a normal 1.5L starter.
2) Refrigerate, let the yeast settle out, decant, swirl up into solution, and then split the starter in half.
3) Save and refrigerate one half.
4) Make a new batch of starter wort, top off the other half up to 1.5L, and let it build back up. Use this, hopefully full starter to pitch.
5) For the next brew, take the saved half, build up a full 1.5L starter, and repeat the process.

Theoretically it seems you could propagate one yeast pack indefinitely this way... I'm sure there are some practical limitations though.
Are there any issues with the process above to be aware of? I'm sure this is basic stuff to you experience folks, but having done just one starter so far I'm still learning about the do's and dont's here.

 

[balrog]

I take a 100b pack and make 1.5L, should be ~300b, let it settle, decant, swirl, save about 1/3 which should be about 100b, pitch the about 200b to my 5g 1.050ish batches.

I go about 6-8 generations, depending on sanitation rigor. Sometimes I get more, but typically at about 6th generation, something different happens -- it looks or smells "different" and that's the end. Others get many more gens.

 

[hogwash]

If you're looking to re-use yeast, check out this thread:

https://www.homebrewtalk.com/forum/threads/yeast-washing-illustrated.41768/

 

[wardens355]

My process is very similar to what you are proposing:

1. Grow extra large starter, generate ~100-200 billion extra cells (based on calculator). I use a stir plate.
2. Pull starter from stir plate and transfer quantity required for upcoming batch into a large mason jar. Transfer remaining quantity into a small mason jar (yeast storage). I boil my mason jars beforehand to make sure they are sterilized.
3. Seal both jars and store in fridge.

I leave the beer in the yeast storage mason jar to avoid opening before I use it for another starter in the future. For the upcoming batch yeast, I'll pull it out on brew day and decant most of the starter beer, then let it warm up slowly while I brew the batch. This system has worked well for me in the past. Only difference with your procedure is that I don't decant before splitting into pitching yeast and stored yeast, just split the entire starter and leave a mason jar full of beer/starter in the fridge until next time I need it.

 

[Gnomebrewer]

Theoretically it seems you could propagate one yeast pack indefinitely this way... I'm sure there are some practical limitations though.

You are correct that there are limitations. Even sitting in the fridge, your yeast population will be mutating, which means a changing ferment profile when you use it. @balrog sums it up with what happens at about 6 generations (some strains change earlier). It's the same with yeast that's stored for a long time. You'll get others saying it's fine, because it will still take off and ferment the beer (there's enough viable yeast) but it will be different to the original (unless you use lab slants etc.). I make a point now of using yeast within 4 weeks (preferably 2 weeks) of harvesting, otherwise it's a bit hit and miss what will come from the ferment. Two local commercial brewers that I know quite well both limit repitches to 8 generations (and that's pulling fresh yeast from a fermenting batch for immediate pitch into a new batch).

 

[ba-brewer]

It is easier to separate out a portion of starter while the yeast is still is in suspension instead of crashing and trying to get thing remixed up. Also if you step up the second half for the current build it will take off faster with happy active yeast.