Maximizing yeast cells

[jamesrm]

For starters and growing yeast to harvest, what will make more yeast? A large volume of low gravity wort or a smaller volume of high gravity wort? Would you get more yeast cells from a 2000ml at .03 or at .04? I know yeast would consume the .03 faster, but would be more food at .04. This is given that a stirplate is being used.

And, if using a stirplate, any need to dose 02 during fermentation?

 

[saq]

A stir plate loosely covered will result in a very very high yeast cell count, gravity of wort wont make too big of a difference, but the common accepted best practice is 1.040 OG.
Check this guide out, it will tell you all you want to know about growing yeast (the purpose of a starter)
MB Raines, Ph.D. - Guide to Yeast Culturing for Homebrewers - Maltose Falcons Home Brewing Society (Los Angeles Homebrewing)

 

[steelerguy]

A high gravity can stress the yeast and then you will be pitching unhealthy yeast. So stick with a larger volume of lower gravity wort. You may also want to step it up. Using your 2000 ml example, start with 500 ml and let the yeast go to town for 24 hours, then add another 1500 ml. I have gotten a lot of yeast in my starters by doing a step up with the first amount being 25-33% of the total.

 

[fratermus]

+1 on the stirplate; even the homemade HBT-style stirplates are very effective at keeping the yeast jostled around.