Sardoman
Well-Known Member
I don't know how helpful this will be for you, because I keep my frozen yeast library in a -80C non-defrosting freezer, but it might give you some idea of the range of conditions that can be used to store your frozen stocks. My method is to grow up a roughly 2inch x 2inch patch of yeast on a malt agar plate, then scrape it off and resuspend it in 1.0ml of 100% glycerol. This doesn't freeze solid at these temps -- it is easy to scrape a chunk out with a sterile toothpick when I want to make a new starter. I have not tested my viability in terms of cell count, but it is good enough for me. When I spread a chunk of the frozen stock onto a malt agar plate I get a solid patch unless I deliberately streak it out to separate individual colonies.