Double Batch in One Fermenter

[rimfire]

On Day One I brew a 5.5 gal extract batch (1.058 OG), oxygenate the wort and pitch double yeast (2 liquid vials of cal ale no starter) into a 14.5 gallon SS conical. On Day Two (within 24 hours) I brew a 5.5 gallon all grain batch (similar gravity) and add it into the same fermenter to make 11 gallons. The first batch doubles as a large yeast starter for the second. I do not oxygenate the second batch (other than incedental during transfer).

Are there any negative issues with making such a large "starter" (5.5 gals at 1.058 OG) on day one - i.e. growing too many yeast cells too fast, stress, oxidation, etc?

If I were to make an even higher gravity wort (i.e. 1.08 imperial stout) would you recommend making a starter for the "starter" (i.e. day 1 make a 2L 1.04 starter, day two pitch starter into oxygenated extract batch, day three fold in the all grain batch).

Thanks

 

[Calder]

I would think you would want to aerate the second wort addition to help the yeast reproduce, otherwise you run the risk of having too few yeast cells for the entire 11 gallons.

I don't know how well your technique will work. It's probably OK for the lower OG wort, but for the higher OG wort, making the 2L starter is probably just good insurance.

 

[rimfire]

I was thinking two vials (100 b cells each) in the super large "starter" batch would at least double to 400-500 billion cells and would be enough for an 11 gal wort. I was wondering if the cell growth is actually much higher due to the volume of starter wort. I hit the FG and the body is a bit thin (prior to aging). However it's not yeasty or sulfury and has mild esters - that's good.