I am trying to gain a practical understanding of yeast propagation, as it relates to starters. I keep seeing something that I just can't make any sense of.
White Labs says that a single stage starter will create a 4-5 times increase in cell count, and Wyeast says it's more like 6 times, almost entirely regardless of the volume of the starter (ignoring the lower end, because obviously the yeast cannot continue once they have fully attenuated). This is for starters that are aerated and agitated.
This means that if you put 100 yeast cells into a 1.040 starter that is 100 gallons in volume, you will end up with between 400 and 600 yeast cells, and then they will just stop reproducing. Obviously, at such a ridiculously low cell count to volume ratio, the properties of the wort would be almost perfectly unchanged, and yet the yeast just stop reproducing. So here you have a 1.039999 wort with almost exactly as much oxygen in it as before you started, and for some reason the yeast in it won't do anything anymore. If you decant off the beer and repitch the yeast into a nearly identical but different 100 gallons of wort, they'll then reproduce up to 1600 - 3600 cells, and then again stop.
Does anyone understand what's going on here? Can you explain it it me?