Originally Posted by ChshreCat
I've heard that distilled water is very hard on yeast. Since there are no minerals or anything in it, it can burst the cell walls of the yeast due to osmotic pressure.
This is correct, the water will rush into the cell to equilibrate the difference between the salt content inside the cell and out side causing it to burst. It's like putting a salt water fish in to fresh water.
If you are not going to store the yeast for long term, you would not need to deplete the O2 levels buy boiling, but if you want to store the yeast for a couple months in the fridge, you need to deprive them of O2 and food as to assure they go dormant till you want to use them again. If they are active during storage there is a chance to develop off flavors from autolysis.