Breaking all the rules of Repitching Yeast

[twgardner2]

I am a relatively new brewer, so I don't have all the brewing equipment that I would like to have yet AND I live in Italy, so I have to wait a long time to receive yeast in the mail and I risk it dying along the way. That said, I have been trying to repitch yeast as much as possible (also just because I think it is cool playing around with yeast). I know all the "rules" about repitching, i.e. low to high gravity, light to dark color, low to high IBU, stick to the same sugar profile, etc. My gut tells me that these things are probably really important if you are entering competitions and brewing at a very high level. At this stage in my brewing development, I am just trying to learn and brew stuff I won't want to pour down the drain.

Here is what I have done recently with a vial of WLP007. Please let me know what you think, whether this should be fine or if I am in for some trouble:

-Pitched vial into an IPA (IBU = 82)
-Harvested from 3 bottles of my IPA into a DME-wort around 1.040
-Pitched harvested yeast into an apple juice starter for a cider
-Pitched most of that starter into a cider, saved the rest
-I plan on putting the remaining yeast from the cider starter into a DME starter and pitching that into an ESB

So, the yeast that will go into my ESB went through the following stages:
1) IPA
2) DME-wort
3) Apple juice-"wort"
4) DME-wort
5) ESB

 

[DannPM]

Yeast may loose the ability to ferment maltose going into a cider that is almost 100% simple sugars like that which means you wouldn't be able to pitch back into the dme or esb.

 

[foltster]

Yeast may loose the ability to ferment maltose going into a cider that is almost 100% simple sugars like that which means you wouldn't be able to pitch back into the dme or esb.

It won't lose the ability all together. The yeasties might not be in the best of health though. If yeast is difficult to obtain I don't think this is a terrible idea, but why not just make all the starters with wort? That would be the safest path.

 

[DannPM]

It won't lose the ability all together. The yeasties might not be in the best of health though. If yeast is difficult to obtain I don't think this is a terrible idea, but why not just make all the starters with wort? That would be the safest path.

Yes, it will completely lose the ability to process maltose. After a few generations, saccharomyces cerevisiae will stop producing the enzyme necessary to convert maltose into simplier sugars. This is why you can not make a starter out of a simple sugar and yeast nutrient mix and why you can't reuse the yeast from cider for beer.

Read about it here in this paper, it goes fairly in depth but the abstract provides and overview of the mechanism by which this process occurs.

 

[foltster]

Yes, it will completely lose the ability to process maltose. After a few generations, saccharomyces cerevisiae will stop producing the enzyme necessary to convert maltose into simplier sugars. This is why you can not make a starter out of a simple sugar and yeast nutrient mix and why you can't reuse the yeast from cider for beer.

Read about it here in this paper, it goes fairly in depth but the abstract provides and overview of the mechanism by which this process occurs.

You said yourself, after a few generations... I would not expect one typical ~1400ml starter with cider to destroy the ability of the yeast to metabolize maltose in the next generation. Doing a 2nd malt based starter should allow the yeast to re-acclimate to beer wort.

Is it a recommended practice? No. Is it likely to be just fine and make beer? I think so.

 

[arturo7]

Do you plan to make a starter for the IPA?

If yes, make a larger starter as mentioned above.

If no, wash the yeast cake from the IPA then divide it for pitching into the subsequent fermentations.


EDIT: there are several threads on HBT about harvesting/washing/storing yeast

 

[Erroneous]

Might be a good alternative to get into yeast slanting or harvesting from commercial beers.

 

[TheMan]

I am not sure why you harvested your own yeast from bottles...it's much easier to harvest from the fermenter after the brew is done. Try this next time.

 

[twgardner2]

Do you plan to make a starter for the IPA?

If yes, make a larger starter as mentioned above.

If no, wash the yeast cake from the IPA then divide it for pitching into the subsequent fermentations.

I do plan on doing a starter, then pitching that into an ESB. It will be a 2L starter.

Might be a good alternative to get into yeast slanting or harvesting from commercial beers.

I do want to try my hand at slanting - its just a matter of finding the time and getting the equipment. Like I said, I am stationed in Italy and don't have great access to good beer. However, I can buy Sierra Nevada at the exchange so I will be harvesting from that for my next Pale Ale.

I am not sure why you harvested your own yeast from bottles...it's much easier to harvest from the fermenter after the brew is done. Try this next time.

Without the gory details, it was basically due to logistics and timing. I went on a 2-week road trip around Europe and wanted something in my fermenter while I was away. I didn't have time to brew before I left, so I took the yeast from my ESB kit I had and threw some apple juice in my fermenter.

When I got home, I had done a bunch of reading on ciders and wanted to try again, so my options were:

1) Rack my first cider 2 weeks early to get to the yeast (I don't have a conical)
2) Wait a week for possibly dead yeast to arrive from the States
3) Harvest WLP400 from my Belgian Wit
4) Harvest WLP007 from my IPA

So, I went with the IPA. Plus, I just wanted to play around with it and see if I could do it.

 

[Saccharomyces]

Yes, it will completely lose the ability to process maltose. After a few generations, saccharomyces cerevisiae will stop producing the enzyme necessary to convert maltose into simplier sugars. This is why you can not make a starter out of a simple sugar and yeast nutrient mix and why you can't reuse the yeast from cider for beer.

Have you actually tried it though? I know of several folks who have used only KV-1116 (a champagne yeast strain) in a barleywine and got 80% attenuation. It is better to use wort for starters, but as long as you provide sufficient yeast nutrients in the starter I don't see why you couldn't use apple juice in a pinch. Apple juice is in fact the recommended culture medium for wine yeast propagation, and I have used it with greater success than wort to capture wild yeasts due to its lower pH.

When it comes to repitching yeast, there are only two rules:

- Do what works for you
- Be sure to wash the yeast thoroughly to remove the trub before re-pitching

First rule you are on the way to learning what works and what doesn't. Keep good notes, and be thorough in your sensory evaluation. Trying samples side by side, and including a "control" which is fermented with fresh yeast, helps a lot.

If you pitch without washing (pitching on a cake) you will get autolysis, and even if it doesn't produce off flavors it will hinder fermentation performance because the dead yeast release enzymes which encourage the other yeast to stop fermenting and flocculate early. Before I knew this I would "pitch on the cake" and as a result I noticed both diacetyl and acetaldehyde in the resulting beer -- the yeast didn't clean up the byproducts that they should have even after two weeks of yeast contact. With washed yeast I don't have any problems as long as the yeast was harvested and re-pitched in a week or less.

Stone harvests their yeast exclusively from their IPA because they had the best performance with the yeast from the IPA. Sierra Nevada never re-pitches yeast from any beer with an SRM of > 10 or so because they found that darker malts (even in a low gravity beer like a porter, or darker crystal malts) lead to poor performance in subsequent generations. Moreover, the best beer for re-pitching from is likely very strain dependent, since various strains of saccharomyces cerevisiae have such a different genetic makeup.

I don't recommend harvesting bottle yeast for more than one generation because you will be putting selective pressure on the more flocculant cells, and you will get lower and lower attenuation with each re-pitch. You may also run into problems with diacetyl and acetaldehyde due to the yeast not finishing fermentation completely before flocculating. For example I tried the Sierra Nevada yeast harvested from a bottle, and I only got 72% attenuation with it whereas I got 78% attenuation when I used WLP001 (same yeast strain) in the same beer recipe.

 

[DannPM]

I just know what I read; a peer reviewed academic microbiology journal and homebrew expert and thee time Ninkasi winner Jamil Zainasheff both warn about negative yeast performance in beer from such practices. I tend to believe those sources a lot more than people's stories and hunches. Harvesting yeast is just using your batch like a giant starter, which is why harvesting a cider batch's yeast for beer is a bad idea.

Jamil Zainasheff says it right on his site, MrMalty.com

Use an all malt wort for starters. The sugar in the starter needs to be maltose, not simple sugar. Yeast that have been eating a lot of simple sugars stop making the enzyme that enable it to break down maltose, which is the main sugar in wort. The yeast quickly learn to be lazy and the ability to fully attenuate a batch of beer suffers.

(Taken from his FAQ on yeast starters here)

 

[ni*]

Yes, it will completely lose the ability to process maltose. After a few generations, saccharomyces cerevisiae will stop producing the enzyme necessary to convert maltose into simplier sugars. This is why you can not make a starter out of a simple sugar and yeast nutrient mix and why you can't reuse the yeast from cider for beer.

Read about it here in this paper, it goes fairly in depth but the abstract provides and overview of the mechanism by which this process occurs.

You're misinterpreting the paper and the citation it provides for this behavior. The paper you linked to says "Gorts (16) first described the glucose-induced inactivation of maltose transport. He noted that the inactivation took about 90 min and was irreversible in the absence of de novo protein
synthesis under maltose-induced conditions." Note the final section: "in the absence of de nova protein synthesis."

This behavior is of great interest genetically, because it tightly constrains the mechanisms by which it could be occurring, but it doesn't say anything about what wild-type (comparatively) yeast does in a natural setting, where it will be continually undergoing transcription and translation.

Page 2246, top, right column explains that they used a strain (created in ref 36) in which they were able to selectively shut down transcription of the maltose permease gene (and a few others), to get around the complication of new protein being produced.

It may well be a bad idea to go from simple sugars to complex ones when brewing, but this paper doesn't show that. The mechanism identified in this paper would be reversed easily within a single generation (by maltose-mediated transcriptional activation of the maltose permease gene).

 

[DannPM]

Actually, if you read the factual premise of maltose permease inactivation that is laid out, not the meat of the paper, that is what supports what I am saying.

You've got Jamil saying the same thing I am here..you really don't need much more than that!

 

[ni*]

No, it really doesn't. Again, you are misunderstanding what is meant by "permanent inactivation". Yes, the maltose permease protein present is permanently inactivated, but this will not hinder the yeast in producing new maltose permease given appropriate stimulation. This is why they had construct a strain of yeast in which the ability to make new maltose permease could be shut down to do the experiment.

As for the rest, as I said, I have no opinion on whether you should or shouldn't be concerned about going from simple sugars to complex sugars (offhand, the absence of selection pressure could result in the loss of the complex sugar metabolic pathway over time, although this happens less quickly than people think it does). I am only saying that this paper doesn't provide evidence for it.

Perhaps an example in humans would help. Aspirin (ASA) permanently inactivates the cyclooxygenase PGHS-2 (probably by acylation of cysteine residues, although it remains a bit unclear). This doesn't mean that after taking a pill of aspirin you will go without functioning PGHS-2 in your body for the remainder of your life: it means that you'll have a very sharply depleted stock of it which will build up again over the next few hours as protein synthesis occurs (which is why, of course, you need to keep taking aspirin). What this paper does is "turn off" the ability to produce more maltose permease (PGHS-2, in the human example) so that they can get a better idea of how the inactivation is occurring without dealing with all of the newly produced protein complicating their results.

 

[twgardner2]

Well, lots of good discussion .

I'm going to try taking the small amount of yeast from that cider starter and put it in a malt starter, then pitch into a beer. I'll let you know how it goes.

 

[ni*]

Anyone confused can resolve the matter easily enough with a highschool-level experiment: grow yeast on a dextrose agar plate for a week or two (or a month, or whatever it takes to satisfy you -- transfer it to a new plate a few times if you're feeling especially stubborn). Transfer it to a maltose agar plate and see if it grows. Having done this many thousands of times (and people think science is glamorous!) I can be pretty confident it will be just fine. This was all resolved well over a hundred years ago.

 

[twgardner2]

So, I've pitched the yeast that had been in an IPA, then in a Cider Starter, into a Malt Starter and they are fermenting like crazy. However, it will be a while before I find out if there are any other ill effects.

Thanks for all the info!

 

[NuclearRich]

Anyone confused can resolve the matter easily enough with a highschool-level experiment: grow yeast on a dextrose agar plate for a week or two (or a month, or whatever it takes to satisfy you -- transfer it to a new plate a few times if you're feeling especially stubborn). Transfer it to a maltose agar plate and see if it grows. Having done this many thousands of times (and people think science is glamorous!) I can be pretty confident it will be just fine. This was all resolved well over a hundred years ago.

It was also proven that too many hot wings can cause Montezuma to seek revenge. Doesn't mean its a good end result.

I would be interested in hearing how the final product tastes, and how it tastes compared to a similar beer that hadn't sent the yeast through the cider.

Science is a funny thing. It can prove things all it wants, but matters of opinion cannot be proven. The science of how beer tastes is still a matter of opinion. (Before I get flamed, it is a matter of popular opinion; in the cases of beer judges, it is an accepted test of who can taste more tastes more discriminantly)

 

[winterparkmg]

TWG2,
YGPM. I'm doing something similar minus the cider, but with addition of fresh packets as well. Hit me up offline for a brew session!
~Wm

 

[Brewitt]

I hope I can contribute something useful to this conversation. The bottom line is that yeast is adapted to use glucose more efficiently than maltose, and many other sugars. The genes for using most other sugars are repressed in the presence of glucose, even if the other sugar is present. When glucose gets below a certain concentration the genes are induced. That usually includes the most efficient transporters (permeases) of those sugars and some of the enzymes for their metabolism into glucose or a related compound that can be shunted into glycolysis, the process that forms ethanol. When cells are moved from glucose into another carbon source it takes time for the cells to adapt by turning on gene expression. The time is generally greater than that needed to turn on the new genes because the mechanisms that keep the genes off need to be inactivated, which takes time, and only then can the genes be turned on, the proteins synthesized and the metabolism started. Although I don't know about these things in the context of brewing, the time it takes in the laboratory is often 2 to 12 hours, depending upon the sugar. In addition, the cell undergoes other adaptations over time that make it grow more efficiently under the new conditions. Presumably, that also contributes to the benefit of starting cells in malt wort. What other metabolites are produced under the two conditions (a critical issue for beer flavor) and what stress the cells experience during the change, I cannot comment on but there are lots of possible issues.

Obviously, the empirical experience of brewers is extensive and increasing all of the time. It is not always easy to meld observations in the lab with experience in the mouth.

 

[Brewitt]

I forgot one other point. Growing cells under a specific set of conditions has the ability to select cells that grow best under that condition sometimes at the expense of cells that do well under other conditions. Consequently, those cells may be poorly adapted to growing or flocculating, or fermenting, under a second set of conditions. These cells may be varients that are permenantly affected (mutants) or transiently adapted. The later can adapt to the new conditions, the former cannot. Jamil and Chris White comment on this in their yeast book and it is a well know phenomenon in the laboratory. This is evolution in progress.