survival of frozen stocks

Elizabeth Harris chlamy at
Wed May 11 14:27:32 EST 1994

In article <2qqt1e$91h at nntp2.Stanford.EDU>, stearns at leland.Stanford.EDU
(Tim Stearns) replied to a post by Bratty John about flash-freezing yeast
cells in a dry ice - ethanol bath:
> I don't know if it makes a difference, but what I have always done is
> to make the cells 25% glycerol and freeze by putting in the -70
> freezer directly.  Although I haven't quantitated viability there is
> no way that we are getting a four order of magnitude drop from one cycle
> of freezing.  I don't think the flash-freezing is a good idea.  

In a survey of the cryostorage literature I did a few years ago, looking
for a way to freeze algal stocks, I found several papers suggesting that
yeast survive much better with slow cooling.  There's a tradeoff between
osmotic damage (worse with slow cooling) and formation of intracellular ice
crystals (worse with rapid cooling), and some cell types have more problem
with one than the other.  Rapid thawing is desirable in almost all cases. 

Elizabeth Harris
chlamy at

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