Growing Mass Amounts of Yeast

[Danderdude]

Howdy homebrewers.

With your experience with yeast, I figure this would be the best place to ask a question like this.

I make some of my own wine, but not beer. I also feed out several steers at a time on a grain-based ration. My old supply of brewer's dried yeast pellets, an ingredient in my cattle ration, has gone belly up, and the only available replacement is $70/cwt. Now, I'm looking at growing and propagating my own as a cheaper alternative.

I understand the principles behind it all, and have read through the reference material in the stickies, but I like second opinions. Keep in mind, I don't want alcohol production, just lots of wet cake yeast.

Should the wort still be boiled? Is it necessary to make wort or could the mash itself be fermented with the grain still submerged? How can you avoid bacterial contamination while supplying oxygen to the mash? What is the fastest propagating strain, or the most stable?

Any advice is greatly appreciated.

Have a good one, and take care.

 

[Nateo]

Do cows like sour things? Barley is lousy with lactobacillus, which is how some people make sour beers. If they don't mind sour, then you could just throw the yeast in the mash without boiling, I guess.

Another option, yeast will eat any sort of sugar. If it's cheaper to get corn syrup or sugar, you could just grow the yeast in that, instead of messing with a mash.

You can't really grow yeast without making alcohol too, but it'll probably just help make the cows fat and happy.

 

[Northcalais40]

There has got to be a cluster of home brewers in Austin that could donate their spent yeast to you.

 

[Nateo]

I know there a few breweries in Austin too. Ask the brewers what they do with their yeast when they toss it. You could get literally tons of yeast from them.

 

[Danderdude]

I know there a few breweries in Austin too. Ask the brewers what they do with their yeast when they toss it. You could get literally tons of yeast from them.

Well, that's just the thing. I literally need 2000 pounds of wet yeast. I wouldn't feel right asking even 20 people to hold onto a hundred pounds each, if anyone even brews in those quantities, and the big name breweries already sell their yeast to mills that dry and resell it for cattle feed.

 

[cockybitz]

We make starters by rigging up a "stir plate." A spinning motor with affixed magnet and a metal "stirring rod" introduce oxygen which is quite significant to yeast production. Any strain of yeast should work just fine, and even granulated table sugar should work just fine. Get a nice temp of about 85* and they'll be going bonkers. Now for 2000 lbs, that might take quite a while. I might imagine 5 lbs of slury produced with 5 lbs of sugar.

 

[ni*]

I really doubt this scheme would be practical. It works for brewers because they get their yeast for free in the process of brewing beer. (In fact, they'd otherwise have to dispose of it.) Let's do some very generous back-of-the-envelope calculations:
$70 / 100 lb dried = $0.70 / lb dried yeast.

Assume your time is free. Assume your labor is free. Assume your material costs (ie, thousand gallon fermenters) are free. Assume it Just Works the first time you try it, so you have no wasted costs. Ignore the enormous amount of carbon that gets pumped out as CO2 during aerobic growth.

That means that you have to get solids (mostly carbon, some nitrogen) into your yeast for under $0.70 / lb. Ignoring the contribution of oxygen (which you get for free, but doesn't play a big role in final yeast weight, since most of it gets respired during growth) that means that you need to be putting in a solid carbon/nitrogen source (discounted by whatever dry weight you need to remove after brewing -- ie, spent grain) for less than $0.70 / lb to break even with your commercial supplier. That's cheaper than most dextrose suppliers. It's cheaper than malt extract. It's cheaper than I can get bulk barley for.

It's possible to reach that with raw sugar, although you'd have to hugely augment the nitrogen in the wort if you used it. But add back those things I ignored initially, and it's vastly cheaper just to buy the pellets.

 

[beerchemist]

Short answer: you can probably grow yeast in a 20 wt% sugar solution supplemented with 1% ammonium salt (sulfate or phosphate). But sugar's probably more expensive than yeast, as has already been pointed out.

Long answer (contains science!):

Brewing yeast strains are generally prototrophic (meaning the yeast can make all its essential amino acids itself), so you just need sugar and a source of nitrogen. In theory, you can grow your yeast in water that has been supplemented with 10-20% sugar and 1% ammonium phosphate (both by weight), and Yeast Nutrient (a mix of vitamins, such as biotin, inositol, and riboflavin and minerals, such as calcium, magnesium, etc--you might be able to approximate this by chucking in a multi-vitamin tablet for every 10 gallons or so). It'll grow faster if you add a protein source like casein, tryptone, or peptone, but I'm guessing you want yeast as a cheap protein source, so the economics of adding protein to your growth medium don't make sense.

http://www.scientificsocieties.org/jib/papers/2009/G-2009-1028-1038.pdf

This paper's on ethanol production, not yeast harvesting, but should give you some ideas.

 

[Danderdude]

ni*,

Assume I have unlimited amounts of corn and wheat costing me $8 and $10/cwt respectively. Assume grinding costs are negligible. Assume water is, as always, .3 cents a gallon. Assume I have farming spray tanks with agitators in sizes from 50 gallons to 1000 gallons at my disposal. The biggest unaccounted for variable there is how much yeast, under ideal conditions, could grow on X amount of grain in a mash. Also consider that the used grain can be spread out on concrete under the Texas sun, dried, and included in the ration.


beerchemist,

The yeast are actually a digestive aid in ruminants. When you feed a "concentrate ration", meaning any kind of grain or dense protein source, it passes too quickly for the gut flora to completely digest it. You end up wasting 20-40% of the grain. However, the addition of live yeast to the rumen (first and largest stomach, no acidity, where grass is made to sit and be broken down by the flora before proper digestion) frees up the dense nodules of starch left over from the grinding process, allowing more complete utilization.

Starch is just polymerized sugar, and I understand yeast thrive on it as well as they do on straight sugars.

Now, the big questions still floating around are things like, should the mash be boiled? Should the grain be sprouted first to increase the sugar content? Should it be filtered before fermentation? How easily can a mash full of yeast be tainted by wild bacteria? Just how much yeast can grow from a given amount of grain or wort? What is a good example of their conversion ratio? Would sun drying kill the yeast, or do they need to be vacuum or cold-dried?

 

[ni*]

Ah, yes -- I hadn't realized you also grew crops. My mistake: material cost alone obviously isn't enough to make it crazy. I maintain it's probably crazy anyway, but I don't know as much about agricultural economics as I'd like to. Best of luck in it.

If you're going to be fermenting all that corn, though, it seems like it might be worth considering selling the ethanol you get from the process.

 

[beerchemist]

Yeast usually reaches saturation at about 0.08 lbs/gal (those curves in that paper I linked all level off around 8-12 grams/liter), so you could probably get 80 lbs out of one batch in your 1000 gal tank. But you're going to need to slowly scale up, i.e. a 10-gallon batch should give you enough yeast for a 100-gallon batch, etc.

Unfortunately, these numbers are based on a 22% sugar solution--to get that, you'll need about 5 lbs grain per gallon, coming in way more expensive than just buying the yeast.

I'd say try a test batch in your smallest equipment (or a 5-gal bucket)--sprout the grains, mash 'em at 150 degrees for a few hours, filter, boil it to kill off any bacteria, and ferment away. You may be able to get away without filtering, especially if the spent grains are going right back into the feed.

Good luck!

 

[Danderdude]

Yeast usually reaches saturation at about 0.08 lbs/gal (those curves in that paper I linked all level off around 8-12 grams/liter), so you could probably get 80 lbs out of one batch in your 1000 gal tank.

Now that's why I came here. So in sugar solution, you're not going to get more than a tenth pound of yeast per gallon during fermentation. I'd bet that high starch saturation would allow a higher population, as well as regular O2 agitation.

Ok, I think I'll do 4 gallons or so tonight, mash it, boil it and go into a sterilized bucket. Pitch some Fleishmann's and stir it with compressed air several times a day.

But, without filtering it, how would I tell the actual content of yeast in the finished product?

Also, would yall like to see any results?

 

[ni*]

I would certainly be curious.

Mashing unmalted grain alone will not result in much (if any) conversion. You will need at least a portion of your grain to be malted. Otherwise, you can go without mashing and rely entirely on the endogenous yeast amylases to break down the starch, but this will be very slow and inefficient.

 

[beerchemist]

But, without filtering it, how would I tell the actual content of yeast in the finished product?

You can't, really. Even if you compared dry weight going in and coming out, you'd still have loss of mass from the sugar converted to CO2, gain in mass from the yeast produced, etc., and even the yeast slurry you get out will have proteins and other junk mixed in with it. Might be worth filtering the first few test-runs just to get an idea of your yield before trying with the grain in place.

And I'd like to see the results, too. Usually, our focus is on how best to make clear, tasty beer (some of us even have day-jobs working with yeast in a non-brewing manner!). But there's no reason why you can't boil the whole grains and ferment while they're still there.

Do watch this "educational" video about fermenting corn, first:

http://dsc.discovery.com/videos/brew-masters-chicha-videos/