# Yeast



## DanC (Mar 24, 2006)

Can anyone tell me why you need to add yeast to fruit fly culters? I've been experimenting with not using yeast and I can't tell the difference. Anyone have any input?

Thanks,
Dan
http://www.dansrainforestgems.com


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## bluedart (Sep 5, 2005)

The yeast, once grown, serves as food for the adult flies. Chances are that you used flies from cultures with yeast in them to start the cultures without the added yeast. The adult flies probably carried yeast spores with them from the other culture.


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## DanC (Mar 24, 2006)

*yeast*

So by droping one or 2 chunks of yeast thats enough to feed the flies? Than whats the media for just the larva? Just trying to figure this out. I found that if I use too much yeast it makes the culture watery. So I stopped for the last 2 cycles and I can't see a noticable difference. Thanks for the input!!

Thanks,
Dan
http://www.dansrainforestgems.com


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## Smogre (Aug 11, 2006)

Ever see flies on some meat left out?
Meat is a great source of protein which I will assume helps the larva grow.
When you have potatoes this is a source of sugars and it will give the yeast something to eat and break down. The byproduct is a high level of protein and vitamin B.
If your culture is more watery with more yeast, it could be that the yeast is extracting more sugar from the source resulting in a higher liquid content and leaving behind less bulk or husk.
When you add more yeast do you find that your cultures don't produce as well?
I don't know diddly about cultures but in my brewing experience I understand this to be the case.
People talk about killing bugs with CO2. I wonder if too much yeast in the culture could kill you bugs. Another fine byproduct of yeast and sugar is CO2.
Just throwing this out there. I'm not a chemist.


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## Ed (Sep 19, 2004)

The flies carry yeast from one culture to the next so over time the yeast carried by the flies will adapt to your culture methods and maximize its own production however the amount carried on the flies is small so adding more yeast (live active yeast (I am not talking about brewer's yeast yet)) in the beginning helps prevent the culture from being over grown by bacteria or other unwanted contaminates. 

If you are referring to brewer's yeast (which is not active (dead)) and not the active yeast it is added to the cultures to boost production as one of the limiting items is protien and the yeast supplies the extra protien. 

Ed


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## Ben_C (Jun 25, 2004)

> People talk about killing bugs with CO2. I wonder if too much yeast in the culture could kill you bugs. Another fine byproduct of yeast and sugar is CO2.


It can kill bugs if the culture is sealed off. A lot of people have springtail culture die-offs because they feed too much yeast and then seal their culture back up. I don't think it would kill flies so much though because there's typically some air exchange in the culture...but I guess if CO2 production > air exchange then we'd have a bunch of dead flies/larvae.

A bit off topic, but a neat trick for those of you who feed out larvae instead of adults: pump gas (CO2 or ideally N2) into the culture. The larvae will come out of the food and head up. YOu can then just add water (they float fairly well) and pour them over a filter then feed...


~B


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## Smogre (Aug 11, 2006)

Ed said:


> The flies carry yeast from one culture to the next so over time the yeast carried by the flies will adapt to your culture methods and maximize its own production however the amount carried on the flies is small so adding more yeast (live active yeast (I am not talking about brewer's yeast yet)) in the beginning helps prevent the culture from being over grown by bacteria or other unwanted contaminates.
> 
> If you are referring to brewer's yeast (which is not active (dead)) and not the active yeast it is added to the cultures to boost production as one of the limiting items is protien and the yeast supplies the extra protien.
> 
> Ed


This does make sense. So the yeast on the flies is a naturally occuring yeast similar to how a Lambic is made. (Certain sour beer)
Adding more yeast to the culture simply boosts the already present yeast giving the flies more protein to feed on. I can see how it mutates as the process continues but that doesn't really matter when we're feeding flies.

As a side note: Dead yeast has more to do with the glycogen reserves in the husk. Older yeast tends to have less in reserve and you can deplette those reserves. That results in a dead cell or autolysis. So by in large, brewers yeast is not dead. It's just inactive until given oxygen and a food source. aka sugar

Hah! Now that I think about it, this serves as a great way to use my older yeasts from my beer...I'll just dump a cake of it on some potatoes and viola!


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## Roadrunner (Mar 6, 2004)

yeast slurry is a great additive to fly cultures. just gotta get the right consistancy so the flies dont drown.
the lambic your referring to has bacterial fermentation to sour the beer. the monks who make it just open the windows and let the endemic yeast strain ferment the beer but there is also bacterial fermentation which sours it. i have a raspberry lambic that has been fermenting 6-7 years now. i think it`s time to bottle it. just think another 5 years and i`ll have a case of beer. nice thing about beer brewing is that its a tax write off since the final product is yeast for my ff cultures. :lol:


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## Grassypeak (Jun 14, 2005)

Welcome to the list Smogre. Your conceptual recipe sounds good. Aaron (from Aaron’s Frog Farm) sometimes sells cultures that contain the dregs of his homebrew production. He says that these cultures produce better than his standard cultures. Don’t forget to add vinegar to prevent mold (the vinegar can make up ½ the liquid ingredients. My personal formula is as follows:

1 small jar fruit baby food
Same small jar full of vinegar (I use cider vinegar) 
1 teaspoon full of a bakers yeast product.
Thicken this mixture with Gerber’s wheat and banana baby cereal.
Add accordion folded index cards as a pupation substrate. I accordion fold two cards together so that the thickness is greater. I use three sets of index cards per 32 Oz culture.

These cultures look sort of moldy in a week or two but their production is explosive.

As to your initial question about CO2, it has been implicated in the death of quite a few frogs, who have had new “vacation cultures” added to their quarters. The new cultures produce quite a bit of CO2 which can collect in low areas of a viv.

On a side note; isn’t Lambic fermented with a Bacillus sp?


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## Smogre (Aug 11, 2006)

Thanks for the welcome Chris.

I'm always excited to learn how a current hobby relates directly to another hobby. How did I get into brewing you ask? I needed CO2 for my calcium reactor. Called a brew shop, went to the brew shop, bought brew supplies and then had two hobbies! Now I have yeast slurries to grow bugs for frogs.
hah! It's like a bloody circle of life in my house!

Good point on the vacation culture and too much co2. I hadn't considered that. I don't understand the filter pad concept yet but I haven't searched on it much. I'm still figuring out how to build a viv.

I think you're thinking of Lactobacillus or Brettanomyces lambicus

frogfarm,

That's cool that you made a Lambic. I've thought about it but didn't want those cells in my current brewing setup and I don't want to buy specific Lambic gear.


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## pinocchio (Aug 11, 2006)

don't use too much yeast , it will produce CO2. Too much CO2 can kill all the flies ~


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## Ed (Sep 19, 2004)

When I am referring to brewer's yeast I am referring to the yeast sold as a bulk nutritional supplement which is inactivated, not the brewer's yeast sold for brewing.... 

Ed


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