Yeast propagation slants

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May 1, 2008
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I use 20ml autoclaveable vials to make slants for yeast propagation. The method I currently employ is to add sterile wort to the vial and shake it until the yeast is in suspension. I than add the contents of the vial to about 50ml of wort to begin my steps for a starter. My question is can I reuse the agar in the vials? I've recapped the vials and let them sit to see if the culture would grow again but it doesn't. Could I just re-inoculate the slants from the started I just made or is there not enough food left for a new culture? If not, could I reclaim the agar, add more wort, and re-autoclave it to sterilize it and make new slants? I know agar is cheap so the savings is minimal but I like to minimize waste wherever possible. Plus, if I can re-inoculate them that would save a lot of time. How much 1.020 agar is needed for up to 6 months of storage? Maybe I can make 10ml vials and waste less?

Feb 24, 2013
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New Brighton
This is certainly not my area of expertise, but when should that stop me from trying???

It seems like if you autoclave them after you add more wort, they would have to be sterile again. The thing I'm not clear on is whether having any potential "waste" yeast from your last batch might cause issues with your new inoculation? Would that old dead yeast become some kind of food that would be bad for the new yeast? Could it contribute bad chemicals or cause the new yeast to mutate or grow in a non-desirable way?

Would love to hear what someone who knows something thinks.