proofing yeast

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Mark Thorson 12 years ago

I need to add yeast to cut bananas to make food for my Drosophila fruit flies. Currently, what I do is combine 1/2 teaspoon calcium propionate,

3 teaspoons cream of tartar, 2 tablespoons water, and 1 teaspoon yeast in a jar, give it a good shaking, and set it aside while cutting up the bananas. After the bananas are cut up into tiny cubes, I give the jar another good shaking, then pour over the bananas and mix by hand for about
30 seconds. During this mixing, it seems like a lot of liquid comes out of the bananas. Then, I spoon it into the cups where the flies will live.

Until recently, I used a whole package of yeast, which is about 2 teaspoons. I've been battling problems with bacterial overgrowth, and cutting the yeast back to about half has helped a lot. I tried lower amounts, but that seemed to hurt the production of flies.

Giving the jar two good shakings seems to have helped. My theory is that the first shaking mixes the ingrediants and wets the granules of active dry yeast. The time delay while I cut up the bananas allows the water to soak into the granules. Then, the second shaking breaks up the now softened granules and distributes the yeast more thoroughly.

There does seem to be some yeast activity which starts in the jar, even though I've added no sugar or starch. The first food the yeast get should be the liquid from the bananas.

I'm still not satisfied with my results. If I use the whole package of yeast, I lose more cups to bacterial overgrowth, but the best cups produce more flies. If I use half the amount, it seems like the best cups produce less, but I get fewer bad cups.

I'm thinking that maybe I'm not handling the yeast right before adding it to the bananas. Maybe I should add sugar or flour to the yeast at the jar stage, so they'd get started eating earlier. The cream of tartar is a buffered acid which helps to suppress bacterial overgrowth. Calcium propionate is a mold inhibitor which also helps to suppress bacteria. The water is always room temperature bottled water, not tap water.

Any of you yeast-proofing experts out there have any suggestions?

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Sqwertz 12 years ago

Call me bananas for asking the obvious, but why are growing fruit flies?

-sw

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jmcquown 12 years ago

I'm glad I'm not the only person who wondered about why he's feeding fruit flies. Next thing you know he'll start a flea circus. :)

Jill

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Ophelia 12 years ago

I wondered that too??

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Nunya Bidnits 12 years ago

I'll hazard a guess that it's to feed some sort of reptile pet.

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Brooklyn1 12 years ago

Research labs grow fruit flies for medical experiments, etc. because the fruit fly's entire life cycle is only 24 hours.

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Sqwertz 12 years ago

Uh . You're trying to do all that, yet you're asking *us* how to grow a simple single-celled yeast?

Call me skeptical.

Supposing you get that far, how do you capture the sepiapterin? Do you get the flies to pee into little tiny cups?

=sw

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Mark Thorson 12 years ago

I'm growing a mutant strain that makes sepiapterin. Sepiapterin is a precursor for tetrahydrobiopterin, which is an essential cofactor for the enzymes that perform the rate-limiting step in the synthesis of most of the major neurotransmitters in the brain (dopamine, epinephrine, norepinephrine, serotonin, melatonin, and nitric oxide).

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Cheryl 12 years ago

I wondered too unless the fruit flies produce something exotic.

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Cindy Fuller 12 years ago

It's much longer than that, even in the wild. I did a fruit fly genetics experiment in high school. They're pretty precocious critters. They're ready to mate within 8 hours of coming out of the pupae.

Cindy

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proofing yeast

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