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Old 12-07-2012, 09:51 PM   #11
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I think it's wort a try. Stressed yeast is more genetically different than the original strain. Under low stress yeast reproduces by budding so the child cells have almost identical DNA to the parents. Stress encourages yeast to reproduce sexually causing different DNA in the children. This can cause recessive traits to become active in the child cells making them preform different than the parents.
I just read that the brewing strains of S. cerevisiae no longer reproduce sexually at all, but there was no source given. Do you have some data on that? Not questioning, I just always like to have a source! I would have guessed that the changes in yeast from stress were (mostly) epigenetic and expression-based in nature.
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Old 12-08-2012, 12:26 AM   #12
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I've read that yeast in general reproduces both ways, but not heard that brewers strains only reproduce by budding. Maybe I'm reading too much into what I am seeing, but some cells look conjoined. Not like groups of flocculating cells. They look like a bunch of grapes. I'll have to take a picture next time I see it.

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Old 12-09-2012, 12:33 AM   #13
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This is what I am seeing. It's much more clear on the scope than the image here that I took with my cell phone.

(A) Yeast Budding
(B) What looks like conjoined cells to me.

cell-growth.jpg  
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Old 12-10-2012, 01:28 PM   #14
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Is it beneficial to have a lower OG for a yeast harvest when a small amount of viable yeast is suspected? Or, another way to ask... Is it possible to have an OG that is too high for the yeast to work and multiply?

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Old 12-10-2012, 01:43 PM   #15
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Is it beneficial to have a lower OG for a yeast harvest when a small amount of viable yeast is suspected? Or, another way to ask... Is it possible to have an OG that is too high for the yeast to work and multiply?
Sure. I harvest yeast all the time from my IPA and dubbel. I wouldn't try it with my quad or old ale, though. I think it was Chris White that said it's better to use fresh yeast from a bigger beer than older yeast from a smaller beer.

Many strains can ferment up to or past 10% abv. They don't really require any special treatment to take a 1.065 IPA down to 1.012. I think they are good to go for another round.
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Old 12-10-2012, 01:43 PM   #16
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If the beer ferments then the yeast have multiplied. At higher gravities they may multiple less, but they will reproduce. Even if you had a 1.150 wort the slurry at the end would have more cells than were pitched. For yeast propagation the golden number seems to be 1.036 or 9 degrees Plato. This is essentially the peak of the curve when looking at DME per cell produced.

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Old 12-10-2012, 03:19 PM   #17
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Thanks for the info. I'm trying to harvest pacman from 2 different bombers. I used a 1/2c DME with 2c water for the starter. Boosted it once with the same mix. It been over 48 hours and I don't see any yeast. Just the grey-brown trub. There is some krausen-like material floating but it's not too impressive.

Same thing happened when I tried to harvest Chimay. Don't know if I could do anything different for a better outcome. I follow good antiseptic technique and have done other strains successfully in the past. Would a weaker OG wort solution make it easier for the yeast to get started?

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Old 12-10-2012, 03:25 PM   #18
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Thanks for the info. I'm trying to harvest pacman from 2 different bombers. I used a 1/2c DME with 2c water for the starter. Boosted it once with the same mix. It been over 48 hours and I don't see any yeast. Just the grey-brown trub. There is some krausen-like material floating but it's not too impressive.

Same thing happened when I tried to harvest Chimay. Don't know if I could do anything different for a better outcome. I follow good antiseptic technique and have done other strains successfully in the past. Would a weaker OG wort solution make it easier for the yeast to get started?
I think half a cup of DME might be a tad to much for bottle harvesting. Try do a much smaller start. You got remember you don't have much viable yeast in there to begin with. You have to step it up.
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Old 12-10-2012, 03:45 PM   #19
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Agreed. A bottle has roughly 2 billion cells in it. 50ml is a good size for the first step to get things going.

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Old 12-10-2012, 03:58 PM   #20
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Ok. Thanks again. So should I dilute the current project with water or decant and try over with a weaker wort?

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