# yeast needs oxygen



## Ownager2004 (Apr 18, 2006)

Ive read a source or two that says yeast needs oxygen during the first part of its life cycle.... for like 24 hours. Then again ive read on this site that people just mix the batch up and screw the lid on. I geuss there would be dissolved oxygen in the water, but i wouldn't think it would be a 24 hour supply. The source of the information wasn't the best so id thought id ask you guys. 

The reason im asking is my diffusion method isn't the best so i added another bottle to my system. The old bottle is about a week old. I used a t connector to connect the two tubes. Since i read the post about people just screwing on the lid after mixing... i did that without thinking.

Now comes the problem  I geuss what i did was to effectively add oxygen to the old bottle.. a no no im geussing. And also now the old bottle is going to saturate the new one with CO2 and probably drive off some O2.... So far no bubbles  As you can tell im not the brightest person on the block.rogar-Si I geuss some yeast will probably survive, but wont give me an accurate measure of how two bottles will perform on my tank.


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## mrbelvedere138 (Jan 18, 2006)

I am pretty sure a few anaerobically capable bacteria would be able to survive for 24 hours on dissolved oxygen.


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## slickwillislim (Oct 11, 2005)

I did the same thing as you and dont have any problems. I got bubbles a couple hours later after replacing it. If oxygen is added that just means the yeast will do normal ...metabolism or whatever its called and consume the oxygen and create co2 versus converting sugar to co2 and having the alchohol as a biproduct. This is how I understood it but I could be incorrect.


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## acbaldwin (Nov 3, 2005)

I don't have the answer to your question, but you can avoid putting yourself int hat situation by using a DIY gas separator.
http://www.qsl.net/w2wdx/aquaria/diyco2.html
You are looking for the text above this picture:


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## nAD (Mar 27, 2006)

Yeasts are single-celled, the most commonly used yeast is Saccharomyces cerevisiae, which was domesticated for wine, bread, and beer.
Yeast species can have either obligately aerobic or facultatively anaerobic physiology. There is no known obligately anaerobic yeast. In the absence of oxygen, fermentative yeasts produce their energy by converting sugars into carbon dioxide and ethanol (alcohol). In brewing, the ethanol is bottled, while in baking the carbon dioxide raises the bread, and the ethanol evaporates.

An example with glucose as the substrate is

C6H12O6 (glucose) →2C2H5OH + 2CO2

Yeast can reproduce asexually through budding or sexually through the formation of ascospores. During asexual reproduction, a new bud grows out of the parent yeast when the condition is right, then, after the bud reaches an adult size, it separates from the parent yeast. Under low nutrient conditions yeasts that are capable of sexual reproduction will form ascospores. Yeasts that are not capable of going through the full sexual cycle are classified in the genus Candida.

A common medium used for the cultivation of yeasts is called potato dextrose agar (PDA) or potato dextrose broth. Potato extract is made by autoclaving (i.e. pressure-cooking) cut-up potatoes with water for 5 to 10 minutes and then decanting off the broth. Dextrose (glucose) is then added (10 g/L) and the medium is sterilized by autoclaving.

So, adding o2 and bakingpowder or potato dextrose the yeast will reproduce itself. If you add o2, without any nutrients you will end up with less yeast then to begin with.

*Weee* my first post, I hope my bad English isnt any problem  Greetings from Norway !


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## griffin7882 (Apr 26, 2006)

reading some of these posts kinda brought up an old idea i had but never tried. would co2 production be increased or decreased or just stay the same if instead of just having the yeast/sugar/water mixture going to a gas separator, you had an air pump pumping air into the yeast mixture and then the air and co2 going to the gas separator and from there to a diffusor. do you think that would make any difference?


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## acbaldwin (Nov 3, 2005)

Griffin, that would be counter-productive. All of your out-going CO2 would be "diluted" with O2. Just like if you ran an airstone straight to your tank.


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## Amiga276 (Sep 18, 2005)

I know you probably have found lots of recipes for DIY CO2 but here is mine and it works great, lasts about 6 days.

6 cups of warm water (about 103 degree F)
1 cup of sugar
1 teaspoon of dry active yeast

1. In your bottle (should at least be 1.5L) add yeast and sugar. Then Shake until most of the sugar is dissolved.
2. Add yeast and gently stir. 
3. Let the mixture sit for about 10-30 min or until it starts a good foam.
4. Ready to use.

This mixture usually starts producing substantial amounts of bubbles fairly quickly.


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## Ownager2004 (Apr 18, 2006)

good news. The 2 bottles got the fishies gasping at the surface. Had to back down the diffusion a bit but everything looks well


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## yildirim (Nov 25, 2004)

My CO2 comes from a DIY 5lt bottle (lots of sugar, a little portion of wet yeast and baking powder initialy), feeding to the inlet of EHEIM 2213 via an air stone. I pump as much CO2 as possible to my tank and for achieving this I add 4-5 cube sugars every morning after first 3-4 days and change 20% of the water every 3 days and use the same bottle this way for 2-3 weeks sometimes longer. CO2 is on 24/7, I never disconnect it. When I first prepare the mixture I dissolve yeast in a glass of water and wait for an hour or two before adding it to the mixture.


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## Ransom (May 3, 2006)

acbaldwin said:


> I don't have the answer to your question, but you can avoid putting yourself int hat situation by using a DIY gas separator.
> http://www.qsl.net/w2wdx/aquaria/diyco2.html
> You are looking for the text above this picture:
> ...picture snipped...


Just to clarify for those who didn't read the linked article. This "gas separator" is for keeping liquids and solids from getting into your tank, i.e. it separates gases from liquids and solids. It doesn't separate individual gases from each other.


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## jbierce (May 11, 2006)

Connecting two bottles together is easily done; just place a check valve on each one. When the pressure produced by the CO2 diminishes to the point where it's lower than the airline pressure, that bottle then has no affect on the other bottle(s). Placing a bubble counter on each one will show whether or not they need to be re-charged.

On smaller tanks I usually use a 2-liter bottle with 3/4 cup of sugar and 1/2 teaspoon of yeast. It produces CO2 for about 10 days. More sugar if you want it to last longer, or more yeast to produce more CO2 (less time of course).

nAD, your english seems perfectly fine. If you hadn't said anything I would've thought you were from the US or UK. I hope I didn't offend you by that remark, lol

JBierce


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## GedKealmen (Mar 11, 2010)

nAD said:


> In the absence of oxygen, fermentative yeasts produce their energy by converting sugars into carbon dioxide and ethanol (alcohol). In brewing, the ethanol is bottled, while in baking the carbon dioxide raises the bread, and the ethanol evaporates.


Hello all. I'm building my first planted tank... a simple 50x50x26 (cm) tank, so I want to build the best possible combination of generator/diffuser or reactor. I notice almost everyone has the same DIY PET bottle generator design which doesn't add oxygen to the yeast culture.

As far as I can tell (which isn't very far, I'm the first to admit), this design will make the yeast go into anaerobic mode after the oxygen initially dissolved in the water is depleted. This will produce ethanol and ethanol evaporates very easily.

Aren't we adding ethanol into our tanks then? Won't this result in drunken fish, or even dead ones?Shouldn't we try to aereate the culture in order to reduce the anaerobic yeast function?

Also, won't aerobically functional yeast produce a LOT more Co2?

Greetings from Mexico nAD and everyone else!


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## slickwillislim (Oct 11, 2005)

Wow, This is an old thread. I haven't been on here in way too long.

The evaporation of ethanol is very minimal, especially at room temperature. Yeast can only survive to around ~15% alcohol, and that's only specific alcohol resistant strands not your standard bread yeast. Also, we are adding small amounts of evaporated alcohol to a much larger and often heated aquarium. This would mean to me that alcohol would evaporate faster out of the warmer tank with a larger surface area. Alcohol also reacts with other bacteria and gets processed by all sorts of microbes, which should be present in a healthy planted aquarium.

Obviously these are inexact figures I am using to back up real life experiences.

Aerating the yeast would cause more respiration to take place creating more CO2 quicker. BUT we don't just want a lot of CO2 we want JUST co2. This allows us to increase the concentration of co2 in the aquarium quicker and more reliably. 

The method you describe would work, and is similar to some people filling garbage bags with their exhaled air and rigging it up to a air pump... But your going to use more sugar since respiration will be happening faster, and you will be bubbling a lot more out.


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## huaidan (Mar 6, 2010)

Yeast are capable of aerobic and anaerobic fermentation. Since aerobic fermentation yields more energy, it is largely catabolic, meaning yeast reproduce and grow more robustly. Brewers like to aerate their batch for this reason. However, numerous problems would arise from continuous aeration: aerobic bacteria which would turn it to vinegar, oxidation of the mix, etc. For purposes of CO2 injection, problems would also arise. It's preferable to inject 100% CO2, aerating a CO2 mix would lead to CO2 escaping, down time, inefficiency, etc.
So, aerate your batch when you start, a good violent shake would do. After that, just swirl occasionally to mix the yeast, no need to aerate.
One thing you might want to consider is yeast nutrient. It's a much more important requirement than aeration.

And I agree about the ethanol. It would get oxidized/evaporated/digested/photolyzed long before it ever became an issue. Among the microbes in your aquarium, in fact, are yeast cells digesting the detritus and producing minute amounts of alcohol. Other microbes are producing organic acids.


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## Diana K (Dec 20, 2007)

The mix (ethanol or other) can be a problem if it really does get into the tank. Not the few stray molecules that follow the same path as the CO2, but if the bottle tips over. 

Set up a separator bottle between the yeast culture and the tank.


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## Big_Fish (Mar 10, 2010)

Diana K said:


> The mix (ethanol or other) can be a problem if it really does get into the tank. Not the few stray molecules that follow the same path as the CO2, but if the bottle tips over.
> 
> Set up a separator bottle between the yeast culture and the tank.


Diana K is exactly correct with this statement..... 
Don't ask how I know that :shock:
VERY good info here folks. Keep the grey matter stirred.


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## WhiteDevil (May 7, 2009)

Also, the kind of yeast used has alot to do with it too, brewers yeast or winemakers yeast react near instantly and last longer and produces more then baking yeast does.

I just started a brewers yeast mix this morning, its been on the tank where as my dry active yeast sits for a day before it can be used and doesnt last half as long or produce half as much.


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