Hello hello,
I am in the process of gearing up to do some frozen yeast banking and -- thanks to the kind work of FlyGuy, Kaiser, and many others -- I've put together a procedure I feel comfortable with.
The conventional wisdom seems to be that using glycerin as a cryoprotectant in a ~25% solution is the best way to do things in a home freezer. If I understand correctly, the cold temperature slows down the yeast's metabolism significantly, and the glycerin prevents ice crystals that form in the suspension from tearing the yeast to bits.
But, if cold=good and freeze=bad, is there any reason not to use a higher proportion of glycerin (50%-60%) to prevent the suspension from freezing entirely (cf. freezing points)? It seems this would get us the cold temperatures we want in a gentler environment.
I'm sure I could be missing something here. Perhaps that level of glycerin is toxic to the yeast, or perhaps the freezing is actually necessary for some reason. I'm going to be doing some comparative viability tests and will post the results here when they start coming in, but it's a long term experiment. In the meantime, do any ScienceGuys have thoughts? I've always been impressed with the level of expertise here.
-malfet
I am in the process of gearing up to do some frozen yeast banking and -- thanks to the kind work of FlyGuy, Kaiser, and many others -- I've put together a procedure I feel comfortable with.
The conventional wisdom seems to be that using glycerin as a cryoprotectant in a ~25% solution is the best way to do things in a home freezer. If I understand correctly, the cold temperature slows down the yeast's metabolism significantly, and the glycerin prevents ice crystals that form in the suspension from tearing the yeast to bits.
But, if cold=good and freeze=bad, is there any reason not to use a higher proportion of glycerin (50%-60%) to prevent the suspension from freezing entirely (cf. freezing points)? It seems this would get us the cold temperatures we want in a gentler environment.
I'm sure I could be missing something here. Perhaps that level of glycerin is toxic to the yeast, or perhaps the freezing is actually necessary for some reason. I'm going to be doing some comparative viability tests and will post the results here when they start coming in, but it's a long term experiment. In the meantime, do any ScienceGuys have thoughts? I've always been impressed with the level of expertise here.
-malfet