Author Topic: Yeast Mutation  (Read 2005 times)

Offline ynotbrusum

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Re: Yeast Mutation
« Reply #15 on: December 03, 2020, 01:39:49 AM »
And for what it’s worth, I have taken a lager yeast out 25 repitches with no observed off flavors or performance issues. It took a couple years and I stopped only because I feltI had satisfied myself and wanted to move onto other strains.
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Offline TXFlyGuy

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Re: Yeast Mutation
« Reply #16 on: December 03, 2020, 02:22:39 AM »
And for what it’s worth, I have taken a lager yeast out 25 repitches with no observed off flavors or performance issues. It took a couple years and I stopped only because I felt I had satisfied myself and wanted to move onto other strains.

That's good to know. I've never gone that far, simply due to fear of the unknown. Around 10 generations has been the max for me. But armed with this info, we will continue to re-pitch without being overly concerned.

My yeast has sat for about 5 months, completely dormant. And then re-pitched without any problems. I try to brew faster and re-use the yeast on a more rapid schedule.

The problem arises when you have three, four, or more yeasts in storage.

I have the following, all being harvested:

Kolsch (Wyeast)
London Ale (Wyeast)
Czech Pils (Wyeast)
W-34/70 (Saflager)
Oktoberfest (Wyeast Blend)

The only ones not working right now are the Kolsch and the Czech Pils.

We have 40 gallons fermenting at this time.
« Last Edit: December 03, 2020, 02:24:26 AM by TXFlyGuy »
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Offline Descardeci

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Re: Yeast Mutation
« Reply #17 on: December 03, 2020, 05:03:48 PM »
And for what it’s worth, I have taken a lager yeast out 25 repitches with no observed off flavors or performance issues. It took a couple years and I stopped only because I felt I had satisfied myself and wanted to move onto other strains.

That's good to know. I've never gone that far, simply due to fear of the unknown. Around 10 generations has been the max for me. But armed with this info, we will continue to re-pitch without being overly concerned.

My yeast has sat for about 5 months, completely dormant. And then re-pitched without any problems. I try to brew faster and re-use the yeast on a more rapid schedule.

The problem arises when you have three, four, or more yeasts in storage.

I have the following, all being harvested:

Kolsch (Wyeast)
London Ale (Wyeast)
Czech Pils (Wyeast)
W-34/70 (Saflager)
Oktoberfest (Wyeast Blend)

The only ones not working right now are the Kolsch and the Czech Pils.

We have 40 gallons fermenting at this time.

Mutation is complex thing, is hard to observe with some organism and easier in others, there artificial and natural selection and genetic drift, those all can enter the count to change the yeast, but I don't think this is really a problem in brewing, you're using a single strain, the mutation can be for a little change of flocculation or attenuation or nothing, but the enviroment you're creating will favor those without mutation, the select strains that the lab sell to you, you're not change too much the enviroment, you're give the same sugars all the time you make beer, same pH, or close, and is not adding another organism to compete with the yeast so mutation can happen but I don't think it will afect your beer, I'm speaking this a biology, but I'm not a expert on yeast mutation or nothing like this, just give my thoughts

Offline hopfenundmalz

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Re: Yeast Mutation
« Reply #18 on: December 03, 2020, 06:12:41 PM »
How long is a piece of string? 

Tommy previously answered this question:


2*pi*r exactly. r depends on the radius of circle the string fits around.

From another post:


I recall a Dr Bamforth interview where he said he was given a lecture in England. He said something like he prefers not going into double digits repitching before a replacement pitch is grown from a master colony. A gentleman in the back stood and said they’re on something like their 4000th+ repitch at last count!



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Harveys claims to have used the same yeast for 50 years or so.
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Offline TXFlyGuy

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Re: Yeast Mutation
« Reply #19 on: December 03, 2020, 08:50:04 PM »
The same yeast for 50 years? Is the strain always harvested?

Or are there scientists with white lab coats propagating the yeast cells to ensure that the strain remains pure?
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Offline hopfenundmalz

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Re: Yeast Mutation
« Reply #20 on: December 03, 2020, 11:34:52 PM »
The same yeast for 50 years? Is the strain always harvested?

Or are there scientists with white lab coats propagating the yeast cells to ensure that the strain remains pure?

How about 63 years? I don't know all the answers, but watch the video.

https://www.harveys.org.uk/news/60th-anniversary-harveys-yeast

I have really enjoyed the Harvey's beers that I've had in England.
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Offline TXFlyGuy

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Re: Yeast Mutation
« Reply #21 on: December 04, 2020, 02:22:27 AM »
The same yeast for 50 years? Is the strain always harvested?

Or are there scientists with white lab coats propagating the yeast cells to ensure that the strain remains pure?

How about 63 years? I don't know all the answers, but watch the video.

https://www.harveys.org.uk/news/60th-anniversary-harveys-yeast

I have really enjoyed the Harvey's beers that I've had in England.

Good story, thanks. I'll see if we can go a few hundred generations!
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Offline Northern_Brewer

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Re: Yeast Mutation
« Reply #22 on: December 04, 2020, 09:26:10 AM »
It's complicated, not least because it depends massively on your cropping regime - top-cropping an open fermenter at high krausen and repitching every week as in a traditional British brewery will give much happier yeast than something that's been swilling round the bottom of a conical for weeks.and then left in a fridge for a few months. It also depends on the strain, some are just more "fragile" than others.

General view seems to be that typical bought-in yeast in commercial conicals is good for about 10-12 repitches and then it becomes a bit of a lottery. Apparently the Conan at the Alchemist can be run for 50 generations but after 15 or so it gets into a cycle of "bad" pitches and then "good" ones. I suspect part of what's happening in these old British multistrains (and the Harvey's one is not particularly old by these standards) is that you have different strains cycling at different rates, which gives the appearance of a blend that's fairly robust.

Offline TXFlyGuy

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Re: Yeast Mutation
« Reply #23 on: December 04, 2020, 11:52:59 AM »
We toured the Hoffbrau Brewery last January, in Munich. They re-pitch through the 3rd generation, and then start with fresh virgin yeast. They indicated too many issues with maintaining the same yeast quality and flavor profile is why they don't go beyond 3 generations.
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Offline Saccharomyces

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Re: Yeast Mutation
« Reply #24 on: December 05, 2020, 12:40:24 AM »
We toured the Hoffbrau Brewery last January, in Munich. They re-pitch through the 3rd generation, and then start with fresh virgin yeast. They indicated too many issues with maintaining the same yeast quality and flavor profile is why they don't go beyond 3 generations.

Either they use an unstable yeast strain or they are limiting growth during pitching.  Do they use cylindroconical fermentation vessels?

Offline TXFlyGuy

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Re: Yeast Mutation
« Reply #25 on: December 05, 2020, 01:17:45 AM »
We toured the Hoffbrau Brewery last January, in Munich. They re-pitch through the 3rd generation, and then start with fresh virgin yeast. They indicated too many issues with maintaining the same yeast quality and flavor profile is why they don't go beyond 3 generations.

Either they use an unstable yeast strain or they are limiting growth during pitching.  Do they use cylindroconical fermentation vessels?

Yes.
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Offline Saccharomyces

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Re: Yeast Mutation
« Reply #26 on: December 05, 2020, 01:22:19 AM »
Thanks. In our case with acute over pitching, might that cause mutation?
Note that my 8th generation of W-34/70 seemed just fine after rousing it with some fresh wort. It is now chugging away in another Euro-Lager.

The problem you are experiencing is due to lack of new cell production resulting in a culture that contains too many old cells. Old cells suffer from mitochondrial DNA damage due to reactive oxygen species (ROS).

All cultures are going to mutate over time.  That is how house cultures come about.  Over time, a culture develops variants due to single nucleotide polymorphisms. Allow these variants to continue to mutate and a pure culture is going to a multi-strain culture.  We have to remember what most brewers refer to as culture generation is actually the serial crop ordinal value.  The number of generations a yeast culture has undergone can be approximated by multiplying the serial crop ordinal value by 4.5.  For example, the approximate number of generations serial crop number 7 has undergone since the culture was initially pitched is 7 * 4.25 = 29.75; therefore, the youngest cells in the crop are approximately 30 generations away from the cells that were pitched into the first batch in the serial crop sequence.  If each generation of humans reproduced at age 20, it would take 600 years to produce 30 generations.  That is why yeast is a good organism for genetic research.

With that said, amateur brewers should be able to repitch bottom-cropped yeast many more times than a commercial brewery due to the less stressful environment a 5 or 10-gallon fermentation places on a yeast culture.
« Last Edit: December 05, 2020, 01:24:15 PM by Saccharomyces »

Offline Saccharomyces

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Re: Yeast Mutation
« Reply #27 on: December 05, 2020, 01:24:21 AM »
Either they use an unstable yeast strain or they are limiting growth during pitching.  Do they use cylindroconical fermentation vessels?

Yes.

Do you know the volume of these fermentation vessels in hectoliters?

Offline TXFlyGuy

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Re: Yeast Mutation
« Reply #28 on: December 05, 2020, 02:53:50 AM »
Either they use an unstable yeast strain or they are limiting growth during pitching.  Do they use cylindroconical fermentation vessels?

Yes.

Do you know the volume of these fermentation vessels in hectoliters?

Very large. Not sure about the size. Perhaps two or more stories in height.
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Offline Saccharomyces

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Re: Yeast Mutation
« Reply #29 on: December 05, 2020, 01:47:58 PM »
Do you know the volume of these fermentation vessels in hectoliters?

Very large. Not sure about the size. Perhaps two or more stories in height.

That is a lot of hydrostatic pressure.  That is the problem with tall, cylindroconical fermentation vessels.  They place significant hydrostatic pressure on what is in the cone.  People who dive experience hydrostatic pressure.  If one examines the breweries known for repitching, volume is increased not by growing fermentation vessels up, but by growing them outward.