Experiment: pure yeast culture storage in distilled, sterile water

Prolog: I have been storing yeast cultures on agar slants for the past few months to good effect. It's fun and saves gobs of money on yeast; buy it once and you can own and trade it (practically) forever. The technique discussed here might look like yeast washing, but it is different in that the culture[s] are preserved from a pure source and later used for pitching. In contrast, yeast washing brews with the pure source and salvages yeast slurry after fermentation for later use.

I bought two auction lots of Brewing Techniques[1] backissues and am plowing through them. I found an issue containing an article called A Simple, Practical Method for Long-Term Storage of Yeast by Michael D. Graham. This article describes storage of a yeast culture in sterile distilled water, and suggests the cells can remain viable and dormant for well over a year at room temperature. The theory is that the absolute [lack] of food and nutrients causes the yeast to shut down.

This method appears to have several benefits: longer viability than on slants, less cost, less work and less time. Since the recommended volume is only 5cc of water this means the culture tubes can be quite small.

The only downside I see is that the cells must be streaked onto a plate before building into a starter, though many folks streak plates from their slants anyhow.

I have stored two cultures in distilled water "for real", and also stored another culture (Wyeast 1084 Irish Ale) in vials of distilled water for test streaking at 1, 6, and 12 months. For comparison purposes I also dunked the same culture into filtered tap water. It will be interesting to see how it plays out.


In the following pic the three on the left have been innoculated and shaken per the technique. The right three are waiting for innoculation. You can see the milkiness of the tubes with the suspended yeast in them.



The other pic shows my high-tech roomtemp storage container: a Burma Shave mug. The tubes have been sealed with parafilm. BTW, the tubes with autoclavable caps were $50 for 500 off eBay.


I have started a webpage on my site about this process.

BN: I went searching for other information on this technique and found this article on a mushroom site. The distilled water section starts about halfway down the page and describes the basic process.


Fermentationally yours,
Frater Mus

[1] R.I.P. Too bad they are out of business, as this was a pretty great mag.


UPDATE 20090118: I opened up one of the filtered, sterile vials and streaked it out. Made a great plate. Obviously this is too early to be indicative, but does provide hope.
UPDATE 20090415: Made another plate from the vials prepared in Dec 2008. Single cell colonies on the plate; still looks good.