Master vs working yeast sample

[shushikiary]

So I cryo froze my first yeast this weekend. I got my hands on some fat tire yeast and decided I never wanted to run out so I got an international harvester chest freezer (for 25 bucks!!) and it holds a consistent -27 to -30 deg C. Used a 30% glycerin solution on the yeast and made at least two if not more vials of yeast for each strain I had (WLP004, WLP833, and the fat tire yeast).

My question is, after I use the working vial, how do I re-make the working vial from the master? That or do I re-make the working copy from the starter yeast before pitching? I want to make sure I can keep the same strain of yeast without mutation as best I can so I can keep using it for a long long time to come.

I did some searching and reading about this whole adventure and didnt seem to come up with an answer to this particular question.

thanks!

 

[Skyforger]

The big labs have a master sample, and they just take a few cells of it each time to propagate into large batches.

I think the best method would be to 1) have 2 samples of each strain in case something goes wrong; and 2) create a new sample of the strain from the first step-up starter. That is, pitch the small vial into a small starter; after it ferments out, take a bit from it toe make a new vial, and use the rest to step up into a full-size starter.

 

[MalFet]

So I cryo froze my first yeast this weekend. I got my hands on some fat tire yeast and decided I never wanted to run out so I got an international harvester chest freezer (for 25 bucks!!) and it holds a consistent -27 to -30 deg C. Used a 30% glycerin solution on the yeast and made at least two if not more vials of yeast for each strain I had (WLP004, WLP833, and the fat tire yeast).

My question is, after I use the working vial, how do I re-make the working vial from the master? That or do I re-make the working copy from the starter yeast before pitching? I want to make sure I can keep the same strain of yeast without mutation as best I can so I can keep using it for a long long time to come.

I did some searching and reading about this whole adventure and didnt seem to come up with an answer to this particular question.

thanks!

My understanding, based on an extensive conversation with a yeast geneticist, is that mutation is actually virtually irrelevant to homebrewers.

For whatever it is worth, my method is to make eight or ten small vials of each yeast from as pure a source as I can manage when I first get the yeast. Every time you want to use the yeast, pitch it to a starter (or, better yet, plate it and then pitch). Once you get down to just two or three vials left, make a starter and package up another eight to ten vials. By this method, there is no master source. Unfortunately, without a lab grade freezer, I don't think homebrewers can count on a frozen sample to last indefinitely.

 

[shushikiary]

Hmm.. thanks. I like skyforger's idea, but I can see why one would do it the other way too.

I'm glad that mutation doesnt seem to be much of an issue for the home brewer. Just for my curiousity can you give some details as to why? Thanks.

I've read that at -20deg C you can expect the yeast to last 5 years in a glycerin solution, so I'll just re-make the master every 4 or something like that.. lol that or get a true cryo freezer before the 5 years is up.

 

[MalFet]

Check out post #19 in this thread (https://www.homebrewtalk.com/f39/re-using-yeast-whats-science-221788/), were I explained the mutation claim earlier today. (sorry, on the train on my phone right now, so I can't resummarize easily)

@skyforger - does that mean you're firing upthe autoclave everytime you brew? Doesn't that get tedious?

 

[Skyforger]

MalFet: no, I don't use an autoclave every time I brew. Could you explain why you think that's the case? I'm not sure how I implied that, and would like to set the record straight.

Starsan works well for anything that hits the actual brew; for anything that I need actually sterile, such as slants, an oven at 300*F (stepped up somewhat slowly) can work fine. Theres' certainly no contamination at that point.

It's true that mutations don't effect homebrewers much; I think even White Labs suggests that their yeast strains can be used for 5 generations without adverse effects. And that is a very conservative estimate. That's why I don't balk at using a yeast that's been used in a mini-starter as a keeper yeast.

 

[brewingkitty]

i have slants over a year old in my fridge. checked em out today and they're still creamy.

 

[MalFet]

MalFet: no, I don't use an autoclave every time I brew. Could you explain why you think that's the case? I'm not sure how I implied that, and would like to set the record straight.

Starsan works well for anything that hits the actual brew; for anything that I need actually sterile, such as slants, an oven at 300*F (stepped up somewhat slowly) can work fine. Theres' certainly no contamination at that point.

It's true that mutations don't effect homebrewers much; I think even White Labs suggests that their yeast strains can be used for 5 generations without adverse effects. And that is a very conservative estimate. That's why I don't balk at using a yeast that's been used in a mini-starter as a keeper yeast.

The yeast guy I was talking to basically suggested that if 1000 home brewers kept yeast for 1000 generations, he'd expect to see one perduring mutation. I'm still way more cautious than that, but I was surprised.

Glad to hear the oven works for you, and that certainly explains how you can make one new vial at a time without going insane. Thats why I was assuming you were autoclaving every time...the fact that you make up a new storage vial every time you use one, rather than stockpiling a few.

I tried the oven route but always ended up with mold colonies whenever I plated my samples back out. Those spores are tenacious. The only way I could find to get rid of them was the pressure cooker, which is why I make 8 or 10 vials at a time. It looks like you and I are doing basically the same thing, just stockpiling different quantities. When you say you keep one as a backup, do you Keep the same sample in reserve in perpetuity, or are you making a new backup from starters periodically?

 

[RukusDM]

The yeast guy I was talking to basically suggested that if 1000 home brewers kept yeast for 1000 generations, he'd expect to see one perduring mutation. I'm still way more cautious than that, but I was surprised.

Glad to hear the oven works for you, and that certainly explains how you can make one new vial at a time without going insane. Thats why I was assuming you were autoclaving every time...the fact that you make up a new storage vial every time you use one, rather than stockpiling a few.

I tried the oven route but always ended up with mold colonies whenever I plated my samples back out. Those spores are tenacious. The only way I could find to get rid of them was the pressure cooker, which is why I make 8 or 10 vials at a time. It looks like you and I are doing basically the same thing, just stockpiling different quantities. When you say you keep one as a backup, do you Keep the same sample in reserve in perpetuity, or are you making a new backup from starters periodically?

Not everyone has a autoclave, however it seems that a pressure cooker work?

 

[MalFet]

Not everyone has a autoclave, however it seems that a pressure cooker work?

Yep! That's basically what an autoclave is, admittedly with a lot more convenience. I've got a pressure cooker that I bought for $30 that works splendidly.

 

[shushikiary]

I may have to get my self a pressure cooker. Right now I just used starsan, but that was on brand new vials and equipment.

Luckily though out here in colorado we have almost no mold due to how dry the environment is.

 

[MalFet]

I may have to get my self a pressure cooker. Right now I just used starsan, but that was on brand new vials and equipment.

Luckily though out here in colorado we have almost no mold due to how dry the environment is.

I heard a radio program not long ago where the manufacturer of StarSan was saying not to use StarSan for yeast culturing As much as we talk about sanitation, brewing actually has pretty wide tolerances. Much more than, say, home canning. Yeast culturing, on the other hand, is very sensitive. I'd recommend plating out one or two of your vials just to see if they are as pure as you think they are. Not meaning to sound negative...I've just had a few bad experiences before I fully groked how sensitive this stuff is.

 

[shushikiary]

Hmm... Ok well I'll put a pressure cooker on the list of things to get then.

This first time around everything was brand new and never used so I didnt have any yeast to get rid of, just had to do the initial sanitation, so I hope I'll be ok.

but from now on when I re-use vials, etc I'll pressure cook them.

 

[Skyforger]

When you say you keep one as a backup, do you Keep the same sample in reserve in perpetuity, or are you making a new backup from starters periodically?

One probably could keep a sort of 'master sample' in perpetually, but I just tend to select at random. If my sanitation is good, I'm not too concerned. It might be interesting to keep a master sample for a long time, and then see if your working yeast changes compared to it, but I've never done that. I think it would take a long time before you started to see any real drift.