Reused Yeast on over 150 batches

Hey Guys,

I spent a great deal of time with a microbrewery in the last few weeks and learned quite a few interesting tidbits. The most interesting fact I came across was that they ALWAYS re-use their yeast and never get anything new. The owner/brewer mentioned that they've been reusing the same yeast for the last 10 years without any noticeable change in characteristics or signs of mutation.

This seems to go against EVERYONE's recommended max of how many times to reuse yeast. The owner believes that the yeast distributors, of course, want to sell more yeast and to scare you into throwing away the previously used yeast.

By the way, this brewery had some of the best beer I've had in a long while. It completely inspired me to change up a few of my current house brews. I just wanted to point out that this wasn't crappy beer.

Any thoughts on this?

A lot of breweries have their own yeast strain and don't need a yeast bank to help them. I'd bet that its easier to avoid contamination on a larger scale, too. I think as long as your yeast are healthy and not getting contaminated, you should be able to re-use the yeast for a very long time.

Haputanlas said:

The owner/brewer mentioned that they've been reusing the same yeast for the last 10 years without any noticeable change in characteristics or signs of mutation.

This seems to go against EVERYONE's recommended max of how many times to reuse yeast. The owner believes that the yeast distributors, of course, want to sell more yeast and to scare you into throwing away the previously used yeast.

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Mutation isn't really a risk, but genetic drift and contamination certainly are. Under proper harvesting conditions and great sanitation, one can harvest indefinitely. Chris White has said so much many times. That said, with poor handling, yeast can change characteristics in as few as five to ten generations. Good on this brewery for having what sounds to be a very clean system. I'm not surprised that they get great results, but I'm not sure it's fair to say that the yeast distributors are trying to scare people.

What's the difference between mutation and genetic drift? Sounds the same to me

Haputanlas said:

What's the difference between mutation and genetic drift? Sounds the same to me

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Well. Kinda the same and kinda not the same. Generally, a mutation is a big step at once while genetic drift would be smaller steps over time.

I think the OP brings up a very interesting point. Reusing the same yeast over and over again would sort of create a house strain. The yeast would change from what you originally start with. Over time I think it would adapt to your techniques and would settle down to a final version. Of course, it could change again. There is no guarantee that you will like what your yeast changes to either.

there are a few breweries that have been using the same yeast for a century or more

http://www.radio.cz/en/section/curraffrs/budvar-now-using-same-yeast-to-make-beer-for-over-a-century

Which brewery? Local Texas guys? Are they acid washing to eliminate contaminants or just repitching brew after brew? I am just not that confident in my ability to keep wild yeasties and bugs outta my brew/ yeast. I will reuse for 5-8 generations with an ale yeast, but 150...brave souls

TANSTAAFB said:

I am just not that confident in my ability to keep wild yeasties and bugs outta my brew/ yeast. I will reuse for 5-8 generations with an ale yeast, but 150...brave souls

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me either. i use fresh yeast every time, as i don't want to bother with washing/storing/etc the stuff

mutation is growing a 3rd arm. genetic drift is monkeys to humans.


(note, i dont wanna be blasted by anthropologists. i was just making generalizations.)

TANSTAAFB said:

Which brewery? Local Texas guys? Are they acid washing to eliminate contaminants or just repitching brew after brew? I am just not that confident in my ability to keep wild yeasties and bugs outta my brew/ yeast. I will reuse for 5-8 generations with an ale yeast, but 150...brave souls

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One brewery that does this is Anchor. They have used the same yeast for countless years.

1) The biggest issue with re-pitching homebrewing yeast is contamination. Long before most strains will change significantly, a regular homebrewer's yeast stock will be overflowing with bacteria and wild yeasts. Without a lab to assure purity it is cheaper and easier to just buy fresh after using the same batch for a few generations.

2) It is well documented in the literature that some strains can be reused over a hundred times without serious genetic drift, and some can only go 5-10 generations before changes are observed (expecially some lager strains). As a homebrewer it is too time consuming to do these kinds of tests on each of the strains we use. Again it is easier and cheaper to just buy fresh.

It all boils down the fact that we are not commercial breweries, we are looking for great beer and if it costs 1$ extra/5 gallon batch I think most of us would happily pay it.

TANSTAAFB said:

Which brewery? Local Texas guys? Are they acid washing to eliminate contaminants or just repitching brew after brew? I am just not that confident in my ability to keep wild yeasties and bugs outta my brew/ yeast. I will reuse for 5-8 generations with an ale yeast, but 150...brave souls

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Mt. Tallac Brewery in Lake Tahoe. They have the best Amber Ale I've ever had.

I'm not a huge Amber fan, but I've never had an Amber with this much flavor either.

EDIT: Not sure what they do to the yeast, I didn't get to stick around for that. I also didn't ask - Shame on me

Haputanlas said:

I'm not a huge Amber fan, but I've never had an Amber with this much flavor either.

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Maybe it's that 150 generations of bacteria and trub.

AZ_IPA said:

Maybe it's that 150 generations of bacteria and trub.

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That's what I was afraid of.

AZ_IPA said:

Maybe it's that 150 generations of bacteria and trub.

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More than likely they have a commercial service that banks the yeast in a -80C freezer to ensure the yeast doesn't drift over the decades. The lab is probably still scraping cells from samples frozen decades ago to restart their yeast stock. It is all about consistency.

What micro-brewery did you go to? You just hung out there?

Edit- nevermind, looks like it was in Lake Tahoe.

theredben said:

More than likely they have a commercial service that banks the yeast in a -80C freezer to ensure the yeast doesn't drift over the decades. The lab is probably still scraping cells from samples frozen decades ago to restart their yeast stock. It is all about consistency.

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That part I do know. They do everything on site. The yeast doesn't leave the brewery.

I don't think it's uncommon, brew pubs are notorious for re-pitching yeast in perpetuity. Really, I think it's a matter of common sense: if the beer is coming out great, why mess with it?

On a homebrew scale the repitch rate is going to be lower because you aren't brewing the same beer every 10-14 days, and you have a much higher chance of contamination due to the surface area to volume ratios.

The basic machinery involved in replicating DNA during cell division causes mutation at a defined rate, for yeast this is roughly 10^-8 per number of base pairs in the genome, per generation.

Given that the yeast genome is in the neighborhood of 12.5 million base pairs, it would take approximately 8 generations before you'd expect to start seeing point mutations in individual cells.

You'd likely need to wait a very long time for one of these to land in a flavor/character altering gene.

All that said, its really no wonder that breweries have managed to keep house strains constant for so long

This is an aspect of homebrewing that I've been puzzled by since I started in on it. With bread, yogurt, or Japanese pickles, the longer a starter has been around, the better. I've heard of Japanese guys saving their pickle jar out of a burning house because they were so attached to their culture.
In -every- other instance of fermentation in foodstuffs, the age of the culture is the dominant determinant of quality, and that age is heavily valued.

Mutation is simply the act of replacing, deleting or inserting DNA nucleotides (insertion/deletions can be combined as one term, called indels, as it's often difficult to determine if base-pairs were added or removed.) Almost all of the time the mutations will have absolutely no effect on the function of the altered allele/gene/phenotype/etc.

Genetic drift is all a force of chance. When a new mutation occurs, it has a frequency amongst the population of 1/2N, where N is the population size. Genetic drift is the act of the mutation increasing or decreasing in frequency over generations. It can either be brought to fixation (i.e. all members of the population have mutation instead of "wild-type") or extinction, the latter of which is FAAAAAR more common given the original frequency of 1/2N.

Now put that into yeast population size.... it's pretty improbable that, under good conditions, noticeable mutations could ever occur.

And motobrewer... please don't reference anything involving evolution to "monkeys turning into humans." That is one of the worst misconceptions of evolution and, even if you're joking, it gives creationists fuel for their ignorance. Monkeys and humans exist in the same time-frame, which means there is no possible way one could have evolved from the other. All primates (monkeys, chimps, and apes such as humans) came from a common ancestor. Some are more closely related and have more recent common ancestors; for instance, humans and gorillas most recently diverged in the ape lineage. And before anyone corrects me there is a lot of evidence brought to light recently that puts us genetically closer to gorillas than chimps.

/evolution-rant

Haputanlas said:

What's the difference between mutation and genetic drift? Sounds the same to me

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Genetic drift is basically the increase or decrease in frequency of an already existing genetic trait. If we, for example, gave all the redheads on the planet fancy cars, big houses, and the complete Barry White discography, we'd expect them to become more successful at reproducing than non-redheads. Sooner rather than later, the relative population of redheads in the world would increase significantly. That's not a mutation, though, because there's nothing new coming to form...redheads already exist.

Mutation, on the other hand, is the random appearance of a novel genetic trait within an individual. If a kid is born with a gene for blue hair that none of his parents have, that's mutation.

Mutation risks are relatively low to begin with, and the probability is extremely low that you'll see a transformation that to a) affects the flavor of the beer, b) doesn't kill the yeast outright, and c) actually makes the single mutated cell more adaptive than the baseline variant (and thus allows the variant to dominate the strain).

Genetic drift, however, is very easy to cause. If you want a simple test, harvest yeast from secondary for a few generations. Essentially, you'd be selectively favoring late flocculating yeast over early flocculating yeast. This isn't a mutation, because both late floccing and early floccing are traits already found in the yeast population. But, rather quickly, you'd end up with a population of yeast that was very non-flocculant (and thus...cloudy beer and high attenuation).

I've been reusing commercial yeast for many generations without problems, but I go to great lengths to make sure that my culture is pure and representative. I was mainly objecting to the characterization of the yeast labs as manipulative. Most of the information I have on how to handle yeast properly came directly from Wyeast and White Labs. The 4-5 generations thing is just a good rule of thumb for those who can't or don't want to control their process closely.

Let's say some aliens came to earth to take a sample of humans and start a new civilization on another planet.

If they land in Africa they will most likely select black skinned individuals. That other planet will then be populated with children of black people.

That's why it's important how you select the individual cells that will be allowed to ferment the new beer. You crop from the top? Decant the yeast cake? It can make a big difference very quickly in a few generations without involving any mutation.

MalFet said:

Genetic drift, however, is very easy to cause. If you want a simple test, harvest yeast from secondary for a few generations. Essentially, you'd be selectively favoring late flocculating yeast over early flocculating yeast. This isn't a mutation, because both late floccing and early floccing are traits already found in the yeast population. But, rather quickly, you'd end up with a population of yeast that was very non-flocculant (and thus...cloudy beer and high attenuation).

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This isn't genetic drift, it is just artificial selection. If you want to have genetic drift, you have to take a random sample... and if you happen to get a larger proportion of late floccing yeast by chance, thereby reducing the frequency of those genes in the population, you've got genetic drift.

TwoDollarBill said:

This isn't genetic drift, it is just artificial selection. If you want to have genetic drift, you have to take a random sample... and if you happen to get a larger proportion of late floccing yeast by chance, thereby reducing the frequency of those genes in the population, you've got genetic drift.

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Hmm...on further research, you are right. I swear I've heard Bamforth/Briggs/Fix talk about genetic drift as a consequence of selective pressures. In any case, the relevant distinction here is between mutative and non-mutative change.

Edit: out of curiosity, how would you make an empirical distinction between random change and selected change?

What about the notion of "stressed" yeast i.e.; after brewing a IIPA? Any reason-aside from the conventional wisdom-not to reuse that yeast?

-d

ps I'm using a 15 year old sourdough culture that has indeed only gotten better tasting & stronger acting. And while it's only been about 6 months, all of my yogurt (2-3 gal/wk) comes from my initial culture.

Reno_eNVy_446 said:

And motobrewer... please don't reference anything involving evolution to "monkeys turning into humans." That is one of the worst misconceptions of evolution and, even if you're joking, it gives creationists fuel for their ignorance. Monkeys and humans exist in the same time-frame, which means there is no possible way one could have evolved from the other. All primates (monkeys, chimps, and apes such as humans) came from a common ancestor. Some are more closely related and have more recent common ancestors; for instance, humans and gorillas most recently diverged in the ape lineage. And before anyone corrects me there is a lot of evidence brought to light recently that puts us genetically closer to gorillas than chimps.

/evolution-rant

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ug, i knew it. i even wrote a note. oh well.

motobrewer said:

ug, i knew it. i even wrote a note. oh well.

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But I'm not an anthropologist.... I'm a biologist

And sorry, I've been writing papers like crazy lately and it's frustrating to be told that what I study and what I eventually plan on doing for a living is not only a lie but I'm a bad person for doing it too.

So I apologize... I've had my coffee and I can reword this: Making generalizations such as that worry me because it leads misinformed individuals to make further misinformed assumptions which sets our country back compared to the rest of the world. I think almost half of American don't believe in Evolution.




But sorry sorry, let's get back on topic.

Malfet:

Edit: out of curiosity, how would you make an empirical distinction between random change and selected change?

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Well it's actually hard to make the distinction empirically but there are assumptions that can be made based on how the evolutionary community defines "random." As far as I can remember, any bias added whatsoever pretty much makes it non-random. Doing a google search didn't yield me an official definition but I'll ask my professor today!

If you were to want to harvest yeast and have it truly be random, I would think you would have to mark your fermenter with an X,Y,Z coordinate system and use a random number generator to determine which point in your brew to pull yeast from.

Mutation is common in brewers yeast(more so lager than ale), one of the most frequent being so called Petite Mutants, which occur spontaneously in .5%-5% of each generation. They appear much smaller than normal cells upon magnification(hence the name petite) and the mutation is they fail to develop a mitochondria, which means the cells lose the ability of respiration. Petite mutants could lose there ability to utilize fermentables(Maltose and Galactose), could have much less tolerance to stress factors like temperature and ethanol, could produce fusel alcohols and precursors to diacetyl, and usually lose their ability to flocculate. That being said, if the brewer is taking care to have very good sanitary procedures, not using yeast that has been stressed by high gravity beers, and harvesting the most healthy, middle portion of the yeast, he could have success repitching over and over again. Petite mutants would flocculate out last(so most likely they wouldn't be harvested) or not at all and remain in the beer, but if the brewer is filtering they would be removed and would not have a chance to autolyse and cause off flavors. There are breweries in England(and other locales), making low alcohol session beers that have been reusing the same yeast for over a hundred years or more, and they make some really good beer. The only thing I would contend is when in the original post the brewer says he hasn't seen any mutations, he must mean he hasn't experienced any problems with fermentation or tasted any off flavors related to mutation. If he is examining the yeast through a microscope he would no doubt see some form of yeast mutation, most likely petites.

I get the impression (largely, I think, from Noonan's "New Brewing Lager Beer", but maybe, too, from Zainasheff and White's "Yeast"), that part of a brewery's maintenance of a house strain over time is periodically reculturing the pure strain in their own onsite lab. Granted they couldn't PERFECTLY reestablish the identical population, but with attention to the phenotype, maintain a consistent, clean product.

Reno_eNVy_446 said:

If you were to want to harvest yeast and have it truly be random, I would think you would have to mark your fermenter with an X,Y,Z coordinate system and use a random number generator to determine which point in your brew to pull yeast from.

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So, from a practical homebrewer's perspective, what about waiting until fermentation is finished and the beer has cleared, then decanting the beer (i.e., bottling/kegging) and mixing the yeast slurry so that it's a relatively homogenous blend of the yeasts that flocc'd at various points in the fermentation. If you use a jar of this "mixed" slurry, would you be avoiding selective pressures more so than if you're top-cropping or pulling the cake after a few days?

This is true JayBullen! But I was under the impression that the vast majority of Petites occur in the non-coding section of the genome and thus would have any expression.

And your last statement is definitely the truth-fact: a mutation doesn't mean that a yeast cell is going to have a faux-hawk or be like a super-yeast that can ferment an entire batch by itself. Mutations are simply a change in DNA nucleotides, most of the time just ONE nucleotide, and 75% of the time that nucleotide is substituted for the exact same one or another that will cause the translation of the same amino acid (i.e. no change.) In fact, every single one of us is born with on average 3 point-mutations (single nucleotide substitution, deletion or insertion) that our parents do not have.

winnph said:

So, from a practical homebrewer's perspective, what about waiting until fermentation is finished and the beer has cleared, then decanting the beer (i.e., bottling/kegging) and mixing the yeast slurry so that it's a relatively homogenous blend of the yeasts that flocc'd at various points in the fermentation. If you use a jar of this "mixed" slurry, would you be avoiding selective pressures more so than if you're top-cropping or pulling the cake after a few days?

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To some degree, yes this is random. But if one were to nit-pick (and I guarantee someone would mention this; there are nit-pickers in the scientific community that would make you want to kill yourself) you could say that you have selected for more highly-flocculant yeast as you have racked off all the yeast that is still in suspension.

EDIT: But from the practical homebrewer perspective, to answer your question: yes.

I'm sure some breweries go this route:

Yeast from Batch #1 -> Yeast from Batch #2 -> #3 -> #4 (etc)

And I'm sure that others (including my homebrewery!) go this route:



Batch #1 -> Batch #2
Batch #1 -> Batch #3
(...)
Batch #1 -> Batch # X -> Batch # X + 1
(...........)-> Batch # X -> Batch # X + 2

And so on.

I always divide my new yeasts into 3 to 10 for future use. The ones I don't use too often, I only divide in 3-5.

M_C

Reno_eNVy_446 said:

To some degree, yes this is random. But if one were to nit-pick (and I guarantee someone would mention this; there are nit-pickers in the scientific community that would make you want to kill yourself) you could say that you have selected for more highly-flocculant yeast as you have racked off all the yeast that is still in suspension.

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True, though if a yeast cell can remain in suspension for 1-3 months after fermentation is finished (about how long I usually leave my beers in primary), I'd guess I'm probably better off not selecting that yeast for anything other than a wheat beer or similar style where cloudiness is desirable.

Misplaced_Canuck said:

I always divide my new yeasts into 3 to 10 for future use. The ones I don't use too often, I only divide in 3-5.

M_C

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Yeah, same here. I usually do about 3-4 jars of washed yeast or slurry from each batch. Then, after drinking the batch, I decide (based on the batch I just drank) whether that's the batch I want to use as my next generation of yeast once I run out of the current generation of that strain. Never really have "off" tastes, but sometimes there's more or less yeast character, and depending on the strain I might prefer either more or less.

winnph said:

True, though if a yeast cell can remain in suspension for 1-3 months after fermentation is finished (about how long I usually leave my beers in primary), I'd guess I'm probably better off not selecting that yeast for anything other than a wheat beer or similar style where cloudiness is desirable.

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This, too, is the truth-fact.

I don't reuse yeast from the primary... I split the yeast prior to pitching. I trust my starter techniques better than my brewing techniques


M_C

winnph said:

Yeah, same here. I usually do about 3-4 jars of washed yeast or slurry from each batch. Then, after drinking the batch, I decide (based on the batch I just drank) whether that's the batch I want to use as my next generation of yeast once I run out of the current generation of that strain. Never really have "off" tastes, but sometimes there's more or less yeast character, and depending on the strain I might prefer either more or less.

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Misplaced_Canuck said:

I don't reuse yeast from the primary... I split the yeast prior to pitching. I trust my starter techniques better than my brewing techniques


M_C

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Ahh, see I feel the opposite. My starters are warmer than ideal (ambient plus heat from stir plate), under constant oxygenation (stir plate), and are usually just DME and nutrient (rather than all-grain wort), so I feel like I'd rather collect yeast that has brewed a beer than one that has been in an artificial rapid growth chamber.

Well if you collect from the starter, and that the beer you made from that same starter turns out fine, you're pretty likely to have a healthy starter! If the downwards product is good, that means that the upwards product is good too... I'd think

M_C

winnph said:

Ahh, see I feel the opposite. My starters are warmer than ideal (ambient plus heat from stir plate), under constant oxygenation (stir plate), and are usually just DME and nutrient (rather than all-grain wort), so I feel like I'd rather collect yeast that has brewed a beer than one that has been in an artificial rapid growth chamber.

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