So last night I tried to make a frozen yeast bank. I had small 15ml tubes that I filled 1/2 with yeast 1/4 with sterile water and 1/4 with Glycerine. I put it in the freezer and it froze! My understanding was that the Glycerine was suppose to make it so that the yeast would not freeze. Is this true or will it freeze and not puncture cell walls. Got any advice? Thanks