Continuous fermentation

[Grayson_Stewart]

Brought over from old forum

gjbloom
(stranger)
07/02/04 12:39 PM

Continuous fermentation

As I understand it, fermentation is stopped by rising ethanol concentration. I also recall that yeast is a facultative anaerobe, and though it performs better in the presence of oxygen, it can go without. I am wondering whether one could simply perform a vacuum distillation of ethanol from the wash at a temperature that yeast would tolerate, and thereby allow fermentation to continue? Also, does anyone know whether the partial pressure of ethanol increases as the overall pressure decreases (yielding better separation)?

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Anonymous
(Unregistered)
07/04/04 07:56 AM

Re: Continuous fermentation new [re: gjbloom]

That's a fascinating idea... I have no idea if it could be done but I would love to find out.

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Yttrium
(journeyman)
07/04/04 08:27 AM

Re: Continuous fermentation new [re: Anonymous]

The main problem with this idea is that for every 100ml of ethanol created by the yeast, 40 liters of gas is produced. You'd have a difficult time seperating the evaporated ethanol from the massive amounts of CO2.

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linw
(journeyman)
07/04/04 02:26 PM

Re: Continuous fermentation new [re: Yttrium]

Excellent reason! The lack of reproduction without oxygen would be pretty devastating as well I guess.

Next idea!!

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Fourway
(addict)
07/04/04 04:58 PM

Re: Continuous fermentation new [re: linw]

I know I sound like a broken record... but here it is again...
Pretty much every practical way to get alcohol out of fermented sugarwater was discovered a hundred years before any of us were born.
It's a fun intellectual exercise... but if you think of something that actually works even it little you'll probably find an old expired patent from the 19th century with your idea and some improvements you didn't think of... and if it's not widely in use today it's because it turned out not to be practical some time in the last thousand years.

In other news... you probably aren't going to win the lottery either.
Even if you play.
In fact your chances of winning aren't significantly improved if you do play.
The odds are so astronomically high that you probably have a better chance of an occasional lottery ticket falling from the sky and landing in your pocket.

"Dad was a drunk with a fishing problem". --Ben Willis

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linw
(journeyman)
07/04/04 05:49 PM

Re: Continuous fermentation new [re: Fourway]

Broken record or not, you are absolutely right! There are still those who dream of simple ways of defeating the physical and/or biological laws, though. But, as you say, there is more chance of winning the lottery. Better put your energies into copying the best existing practices - that way you actually get to drink some product!

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Blanchy
(enthusiast)
07/05/04 05:35 PM

Re: Continuous fermentation new [re: linw]

No reason not to try to invent new things.

If you tried to set up a unit like this, you would rely on the carbon dioxide to do most of the alcohol stripping for you. The key would be to have a refrigerated cooler and separator prior to your vacuum pump to separate the ethanol from the CO2. Another question would be how much vacuum can the yeast take before they go belly up. There is a power requirement for the refrigerated cooler and also the compressor which would need to compress the CO2 coming out of the unit. I don't think this would really be a practical unit, but it would be fun to sit down and really run the calcs for it.

People have also experimented with continuously removing a portion of a fermenting mixture, running it through a distillation column, and then returning the bottoms to the fermenter. The fermenter would continously be amended with sugar, nutrients, yeast, and the pH would need to be adjusted.

The system would work best with a really large fermenter so that you are drawing off only a small percentage of the total volume. There are a number of reasons why this has not really been tried full scale and one of the main ones I think is that the yeast in the fermenter is not at its prime, so it is never really fermenting quickly. From a homebrew standpoint, this would be almost impossible to set up, unless you built a continuous stripping column and then set about learning how to actually run such a unit. Sanitation long term in the fermenter is also an issue.

Chuck

Edited by Blanchy (07/05/04 05:41 PM)

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gjbloom
(stranger)
07/06/04 06:50 AM

Re: Continuous fermentation new [re: Blanchy]

I have a feeling that the same phase change needed to boil the wash, even near room temperature, may be lethal to our friendly fungus. The chemical properties of vapor phase h20/etoh are surely much different, especially inside the cell wall. Still, I'd be interested to know if they can survive vacuum boiling.

Also, since there is so much gas that has to be pumped off anyway, it might be reasonable to have a small "leak" that lets oxygen bubble up through the wash, re-fortifying the yeast with a bit of oxygen, despite the otherwise anaerobic conditions.


Overall I agree, it doesn't seem all that practical. It just takes one step toward a dream machine that continuously produces without operator intervention - it would be pretty cool if there were a way to set up a machine that simply takes in nutrients and puts out shine.

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Blanchy
(enthusiast)
07/06/04 01:18 PM

Re: Continuous fermentation new [re: gjbloom]

Apparently this setup, the vacuum one that is, has been experimented with commercially. I believe it was in conjunction with non-alcoholic beer manufacture with an alcohol stream by product.

Chuck

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Anonymous
(Unregistered)
09/19/04 05:41 PM

Re: Continuous fermentation new [re: gjbloom]

freeze distill it. i dont think the yeast will die it will just stop working intil u change it back to normal temp.