# DIY yeast CO2 lifespan



## Silvering (Jun 10, 2011)

I've noticed something interesting that I don't recall seeing anyone mention in their yeast threads, but at just about three weeks into a 2L bottle's run, the color goes from "milky" to "clear" - I'm assuming that this change occurs when the alcohol content of the bottle has gotten high enough to kill the yeast. It definitely smells like beer when I pour out the old liquid. So that might be a good way to check if your bottles are still "live" if you don't have a bubble counter on each one.


----------



## wi_blue (Apr 5, 2005)

I averaged 2 weeks a bottle, though I have been putting a little rice in mine for the last few weeks. I get better CO2 generation though they only last a week.


----------



## Tikulila (Feb 18, 2011)

well the reason the solution becomes clear is because all the yeast die, you will also seee that at the bottem there is some "sand" these are the dead yeast cells. the yeast will start dieing at a specific point, about 2 weeks or so, when it is clear it means all the cells are dead. in theory if you find something to break up the ethanol, you will have a stable enviorment, which will never end.

there ARE ( i think) a few bacteria who will be able to break it up ( not sure, il see) but you will take the risk of them overtaking the yeast.

Also, you can put some chemical which reacts with ethanol but im not sure if there is one which will be safe, before reaction and after.


specialists corrct me, im learnede this in summer course so i might not be very accuret:neutral:.


woulöd be interested to start an expirament, to find out if there is any way to get a better lifespan.


----------



## dstrong (Feb 13, 2011)

The only thing that kills the yeast is the alcohol. A good yeast like a champagne yeast can only survive up to 16%ish (correct me if I'm wrong I don't remember the specific numbers for sure) and I think the best yeast u can buy can only go to @21% but I don't remember what it was. Bread yeast will be far less. Idk exactly but a can't imagine it going past 10%. In order to get the yeast to survive longer you need to dilute/get rid of the alcohol somehow. In theory if you regularily took out half the brew and replaced it with fresh sugar and nutrient mix you should be able to keep it going indefinatly. In order for that to not be a pain in the ass you probably want it in something that isn't a soda bottle. While doing your regular regenerating of the mix I would take notes on your recipe to find out what is most efficient. I actually just made a batch of wine today but it isn't hooked up to my tank


----------



## Silvering (Jun 10, 2011)

I've toyed with the idea of diluting the mix before it runs out, but I haven't been paying enough attention to catch it at the right time! I suppose there's no easy way of driving off the alcohol without killing the yeast - the only way I know of (not being a chemistry person) is heat, and boiling it would definitely not let one keep the yeast alive.


----------



## dstrong (Feb 13, 2011)

You wouldn't really have to boil it because ethanol evaporates at a lower temperature but if you heated it you would be in effect making a still and would probably have some very drunk fish. I guess if you had a homemade bubble counter like a bottle or something the majority would stay in there. Maybe if it got strong enough you could have you own fishtank moonshine.


----------



## Silvering (Jun 10, 2011)

I wouldn't heat it still attached to the tank! LOL I'm not positive that the lower boiling temp of alchol would help a yeast factory - can't remember what temp yeast dies at, but 172F seems a little high for a unicellular organism, considering chicken's well done at 165F. 

Slightly different topic: since the sludge at the bottom of a yeast bottle is dead yeast, I'm thinking that it would be beneficial to the new batch to leave the sludge there - wouldn't that serve the same purpose as adding protein powder? Or can live yeast not cannibalize material from dead yeasts?


----------



## vicky (Feb 18, 2010)

Hmmm, based on my sourdough making days dstrong is on the right track. I suggest when your solution is producing well, but before it slows down, removing 1/4, perhaps even less, and adding that to a fresh batch of your favorite recipe instead of more yeast. Since you probably want at least two bottles going anyway, this would give you a free yeast source, slightly reducing the cost of your mix, at least until it becomes contaminated with something yucky. And any home brewer will tell you the sediment at the bottom is not all dead yeast. Live yeast will also drop out of suspension. though usually not as quickly as the dead stuff.


----------



## Tikulila (Feb 18, 2011)

1 problem, alcohol it heavier than water, so itll be hard to rmove it, and yeast will survide 54 degrees celsius, but ill check more into that


----------



## Tikulila (Feb 18, 2011)

ok, so i did a bit of reaserch and found out a few things. 1st:

< 20 C (68 F > 40 C (104 F) Growth Rate Significantly Reduced 

> 60 C (140 F) Yeast cells Die 

now, if im not wrong, if growth rate is reduced, i dot think itll effect the CO2 pro. we will have to try ( someone)

Etanol boiling P: about 54.

now, yeast will make more co2 if they have air, (oxygen) so if we dissolve it into the water= not alcohol.

(i think...)

so, what do you guys say?


----------



## vicky (Feb 18, 2010)

I'm not really sure what you are asking, Tikulila. Yeast produce CO2 and alcohol as waste products of their metabolism. They have to be growing for that to happen. Yes, they need oxygen - but they also need food, and to have their waste, both CO2 and alcohol, removed. The CO2 removes itself, as long as it is not in a sealed container. The alcohol needs to be removed and fresh food added. I think the easiest way to do that is to make some fresh food, and seed it with a small quantity of the yeast laden old mix. Perhaps you could devise another method to remove the alcohol and add sugar (and/or protein, whatever) but it seems needlessly complex. And if you get the temp a few degrees too high, you kill the yeast and have to start over completely

I'm all for science experiments, but for my fish, I like to keep things simple and reliable.


----------



## dstrong (Feb 13, 2011)

Tilulila is actually correct if you could keep the mix oxygenated there would be no need for sugar and it would produce no alcohol. Yeast breath oxygen and feed on nutrients. They exhale co2 which is where the bubbles come from. When you start a mix the yeast feeds off nutrients and rapidly multiplys until it uses all available dissolved oxygen in your mix. Yeast are the most adaptable organisms on the planet and at this point are in a hostile environment, they essentialy steal and oxygen molecule from the sugar to breathe and the byproduct is ethanol. It is this adaptability that brewers take advantage of. I wonder if you could run an airline in just a yeast/nutrient mix and if that would even help with your ppm of co2. I think it might because it would be co2 rich air. In theory if that worked you would only have to replenish the nutrients and you could keep it going with little maintanence.


----------



## vicky (Feb 18, 2010)

In theory, yeah. OK, back to the sourdough starter. The purpose is not to make alcohol - it is to grow yeast. It definitely produces CO2. You keep it going by using, or throwing away, most of the mix say, once a week or so, and adding fresh water and flour. If you don't do that, it gets too sour, and eventually dies. Now in addition to the yeast, the starter contains acid producing bacteria - without that perhaps it would not get sour. But I still don't see this working. If you are adding oxygen, it has to go somewhere - likely out with the CO2 - potentially causing too many bubbles and driving off the CO2 in the process. Again, in theory, if you have everything balanced just right, you would end up with CO2 and O2 rich water - ideal for both plants and critters. I might try this as a lab experiment, but I would not risk my fish on it. I'm also wondering what nutrients you plan on feeding the yeast if not sugar and why not sugar? In the presence of O2, yeast turn sugar into CO2 and water - or so I'm told.

I'd love to hear how this works but frankly, it sounds like more work, not less.


----------



## Tikulila (Feb 18, 2011)

no, the idea is to dissolve the o2 in the yeast "solution". which is possible, just as you dissolve the 
CO2 in the aquarium, itll also make more co2 and also will be alot easier in long term. and if 10% of the oxygen escaps, as somewone who sdoesnt need it perfect, itll be ok.

there are alot of perameters, for example, when a cell dies, all the nutrients will return to the water, so wit enough newtrints, it is possible, also, you can just make a nutrients solution and add X amount of Ml, it might work, i might try to do an expirament, ( if i can get the needed components.)


----------



## dstrong (Feb 13, 2011)

Yeast eat nutrients such as vitamins and canibalise old yeast hulls. The only thing they use sugar for is to breath when they are presented with an anaerobic environment. Actually too much sugar in a solution can kill yeast just like alcohol. You can buy yeast nutrient made for wine making or home brewing or make your own. Any air input that mixed with the output of the bottle would essentially be co2 rich air. Depending on the size of your yeast colony the yeast would take some or all of the oxygen, and respirate it into co2 which would then go to the tank under the same pressure as the input airpump. There would still be other gasses in the air it would just have more co2 than atmospheric levels which then should be able to raise co2 levels in your tank. How much? I don't know that would depend on tank size, airflow, colony size, ect.. I have never tested this theory but I kind of want to. This method would also make it much easier to get more reliable consistent levels of co2 than a normal yeast generator I would think.


----------



## mudboots (Jun 24, 2009)

Very interesting conversation. So, what is the fungal agent when you do DIY without adding any yeast at all, or are there too many variables to know for sure?

The reason I ask is that I do not add yeast, but have a CO2 bottle (actually just making homemade wine and figured I'd use the gas produced for the tank). I smash up the fruit of choice (mixed fruit last two batches), add clean water and sugar, cap it off and let it do its thing for 3-4 months (no, I do not get much CO2 production after the first 2-3 weeks). I have not testing the alcohol content, but it rather mild, so nowhere near the percent someone mentioned about some of the quality grade yeasts tolerating in the 20% range.


----------



## dstrong (Feb 13, 2011)

The maximum alcohol in the batch will be dependant on two things.

1. How much sugar is in the mix. (The yeast will make equal parts co2 and alcohol by weight)

2. The amount of resistance the yeast posseses(sp?) to alcohol.


----------



## brokefoot (Aug 23, 2011)

I've done a good bit of homebrewing (beer), and I was thinking of trying some good brewer's yeast in my DIY CO2 setup. Brewers regularly "re-pitch" yeast. I don't know how much different it is than baker's yeast, but the brewer's yeast does not die when it stops fermenting. It goes dormant as sugars are depleted and toxins (alcohol) increase. (I'm sure some die, but most don't.)

Dump the bear off, pour in more wort (barly malt solution), mix it up, oxygenate, and it starts again. The second batch will ferment stronger and faster than the first, because it is starting with many times more yeast and doesn't take as long to build numbers.

A number of other solid byproducts settle out of the beer, so re-pitching usually involves a process of separating the cleanest yeast from the rest of the "trub" (misc stuff that settles out).

I guess the point would be that brewers yeast might respond better to dumping out most of the liquid as bubbles slow down, then adding more fresh sugar-water. I tried to re-pitch onto my old baker's yeast once in the DIY and it didn't restart.

One more thought: keeping the temp down to the mid-upper 60's will slow down fermentation and prolong it. I used to put my fermenting beer in a tub of water with a t-shirt draped over it and fan blowing on it. The evaporation cooled it. Maybe just setting the DIY in a bowl of water with a soaked rag around it would slow it.


----------



## mudboots (Jun 24, 2009)

Mixed fruit leftovers are not my favorite for a wine recipe, but it works great for DIY, I've never had to add yeast, just sugar and clean water...









And after a few months I've got a dessert wine that's a little too sweet for my taste (I could always cut down the sugar or let it go another 6 months I guess) but is pretty potent...and most importantly very clean tasting...


----------

