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So if I were to pitch bread yeast, and get to primary fermentation, which as I understand it, is the point at which regular cellular respiration can no longer continue due to a lack of oxygen , which is needed for the electron transport chain. Therefore the yeast switch to fermentation, which produces my desired product, ethanol.

But as I understand it, at this state the yeast are no longer reproducing and are in a survival mode.

Therefore if I were to cut a 2$L$ bottle of my primary ferment in half, and then add more sugar and water to the now separate 1$L$ bottles, and oxygen (if possible), up to 2$L$, would I be able to have the same amount of ethanol produced/would fermentation even occur?

I feel there would be diminishing returns even if it was possible, since yeast can only reproduce asexually so many times, which happens during stressful times, which this process might induce?

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Yes, it is possible to reuse yeast in both beer and wine fermentation - commercial brewers do it all the time for cost savings and batch reproducibility, and although I'm not as familiar with making wine, many sites including this one say it's perfectly fine, as long as the viability of the cells is high enough.

The yeast aren't necessarily in stress-induced survival mode during fermentation, they're just living (and metabolizing) anaerobically. They may no longer be reproducing, or doing it very infrequently, but they'll remain perfectly happy little buggers (that's a technical term) for quite a while. Give them more food (sugar), and they'll keep fermenting. What eventually stops the process with wine is the level of ethanol rising too high for their comfort. If you were to dilute the ethanol out with water, they'd keep going.

Now, I wouldn't recommend doing this indefinitely (some strains may exhibit genomic instability, etc.), but new batches can certainly be produced with existing pitches.

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