# Cell growth factors in different types of yeast starter

Cell growth in a yeast starter is dependent on the volume of starter wort. Palmer states that as a general rule of thumb, a 1 liter starter roughly doubles the cell count while a 3 liter starter about triples it.

Other than the fact that Zainashef cites slightly different figures, I believe that Palmer's rule is an oversimplification. The Mr. Malty calculator distinguishes between a simple starter, an oxygenated simple starter, an intermittently shaken starter, a continuously aerated starter and a stir plate.

However, the tab that selects these options doesn't seem to do anything (at least not on my 'puter). I'm also not sure how Mr. Malty deals with inoculation rates.

So. Are there comparative growth factor estimates available that compare the above starters? And what about reliable growth-vs-volume graphs?

Any pointers in the right direction would be appreciated!

## 1 Answer

If you're comfortable doing the math yourself you could use some bioreactor equations to model the yeast growth.

I would start with the assumption that growth is limited by initial population, glucose (which needs to remain under 5 mM), and dissolved oxygen. The vessel size limits the oxygens rate of diffusion into the solution and determines the initial amount of oxygen available. In an optimized setup, glucose would be supplied at a rate relative to the current population size and oxygen supply would be maximized.

• That is a very interesting suggestion: modeling a fermenter as a bioreactor! Thanks for that, I'm going to look into that. The math doesn't scare me. Jul 10, 2018 at 9:01