PSA: Monitor your Yeast Bank

Much to my horror, recent attempts to revive four(!) different banked yeasts from my library have been unsuccessful. I fortunately have “backups” of the ones I consider most important, the “DCY” yeasts (which reminds me that I need to post an update about the DCambic yeasts, which are still fermenting one half-gallon each) and was able to work from that. But what I had considered my primary source of the two DCambic strains appears to be totally dead after just a few months.

I made a switch about six months ago to banking in isotonic NaCl solution after reading Samuel’s post on the matter. My previous attempts at reviving strains have succeeded, even with vials that were a few months older at the time. So, I’m suspecting operator error at this point and am very unwilling to cast this as a fault of the method. After all, Samuel used it for a while, and this is not a novel method. Possible problems include:

  • Improper solution: I used sea salt, because I couldn’t find a pure salt without additives. A lot contain minute amounts of dextrose, and I was trying to limit any sort of metabolism. Due to unknown levels of other salts in the mix it could require a different amount to be isotonic. I could also just have measured it wrong.
  • Storage temperatures at the back of the fridge were too low. Perhaps they dipped into freezing at times, and the small volume cooled off quickly.
  • I just moved a few weeks ago and somehow they got damaged in transit. Not likely, I don’t think, since I just moved within the same building and they were back in the fridge in just minutes.
  • Or, perhaps, I simply killed the sample while transferring into the salt solution. I had already revised my transfer method to avoid shocking yeast with a hot loop but it’s still a possibility.

The other two attempts were from slants. I have not had any issues in the past even with old slants, but these two for whatever reason opened slightly in storage and the tape around the cap wasn’t enough to hold the air in. They dried out as a result. I have successfully recovered yeast from such a slant before, but I am not so lucky this time–not yet, at least. As a last-ditch effort I will add sterile wort directly to the slant vial instead of picking off with a loop.

In either case, though, this highlights the need for monitoring things and perhaps something as simple as periodically tightening the caps on my vials. I may switch back to slants, at least temporarily, while I figure out what could be going wrong with the salt solution method.

Update: I was able to wake the two slanted strains up from their dead, dried, reddish state by adding sterile wort directly to the slant and shaking vigorously throughout the evening. In addition to having dried off, they were also slanted on media I made very early on that wasn’t ideal. I am surprised, frankly, that I was able to do this.

Update #2: Correcting update #1, it looks like only one of the slants actually yielded live yeast. As for the two DCambic yeasts from the NaCl storage medium, colonies finally are visible a week after plating. This is not unusual for Brettanomyces left at 20-22C/68-72F so this may have been much ado about nothing.


4 thoughts on “PSA: Monitor your Yeast Bank

  1. James Golovich

    I used to do the distilled water storage method and it always worked great until suddenly it didn’t. I switched back to slanta after losing a few strains. I definitely now prefer something I can see

    1. DC Yeast Lab Post author

      Thanks for commenting. That’s unfortunate that you lost a few strains. Did you use distilled water by itself or with a salt?

      I suppose with a microscope the isotonic solution method is also something you can see, but seeing that I don’t have one yet it’ll also be slants for me for now.

  2. eurekabrewing

    Very sad to read your lines. I recently encountered the same problem reviving yeast from my frozen yeast library. I now used up all three tubes of this troublesome yeast strain (isolated from Rogue) and none of them grew. I now have to isolate the yeast again. I then had a closer look at the samples and I could see some kind of fungi. The ultimate proof was visible mold growth in one of the starters. Looks like I got myself a contamination here and the yeasts did not survive that.

    Hard to tell what went wrong in your case. I kind of exclude two of your points (storage temperature, moving). As long as your solutions don’t freeze, the yeasts should be fine. Maybe there are some inhibiting compounds in the sea salt? Or maybe it is (just) a yeast strain specific problem. You used 9 g of sea salt on 1 L of water for the solutions, right? Maybe your local pharmacy carries sterile isotonic sodium chloride solutions. These solutions should be really pure salt solutions (as they are used on humans). Good luck with your yeast banking. Cheers, Sam

    1. DC Yeast Lab Post author

      Thanks, Sam. Sorry to hear about your yeast losses, too. I don’t mind so much with commercial yeasts, but losing strains I’ve isolated myself or gotten from bottles I can’t find everyday are definitely distressing.

      I used 9g sea salt per liter, yes. I didn’t find anything off-the-shelf at the pharmacy that wasn’t also buffered, but I think I can buy pure salt packets there that are for making nasal irrigation solution. However, it’s probably a lot cheaper to buy canning/pickling salt online, which is also additive-free.

      I have a couple of other strains in salt solution that I’ll try to bring up. Maybe it’s something specifically with these yeasts as you suggest.


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