Nan's Nook : Archives : Contams : Yeast
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By Herb Smith (Smkindahrbge) on Tuesday, October 16, 2001 - 02:25 am:

I mix the Brown Rice Flour (BRF) and Vermiculite and Water in the proportions indicated in the archives. Then I take however many 1/2 pint jars I have available, usually about 10, put a spoon of vermiculite in the bottom, then fill to the top measurement mark with substrate, and top off the remaining 3/4 inch of the jar with vermiculite, put on lids, top with foil.

Then I Boil them for an hour or two, let them sit overnight, take them out of the pot until I feel like preparing a syringe to innoculate with. I've had them sit in storage for up to 3 weeks, and only one so far has ever grown any mold (indicating that it was not sterile).

I innoculate with Blue Meanie (a'la STP ripoff-central) mycelium solution, which I have recently used the last of to start another 10 jars. I had another jar of Honey Tek made with the same stuff, but yesterday all the mycelium mysteriously floated to the top of the liquid and now has visible gas bubbles in it, so I imagine that one's terminally ill with something.

Anyway, I inoculate the jars in the Oven, put the foil back on, put them under my bathroom sink, where the a/c from my less frugal neighbor's apt keeps the temp under 86 all the time (Dallas). It is usually around 80, never over 84 or under 78.

Anyway, I let them sit in there for about 4 or 5 days, then they start to show mycelial growth. Before day 14, about 1/2 of them will be 3/4 colonized, the other half stopped at about 50%. No green blobs, nothing but substrate and thick White Fuzz. Most of them stay exactly like that, maybe one or two keep growing to 80 or 90%, then stop.

Getting towards the end of week 3, the still exposed substrate starts to grow what looks like more mycelium, but with brown rice powder embedded in it. It gets fluffier, but it never gets thick and it never turns white. I have one that I started in early August that still looks the same, but the mycelium has shriveled up and stuck to the substrate, I guess dead.

My final attempt (due to broke student syndrome) was to put them all in a tupperware box with a HEPA filter. I'm thinking that I should try B+ next time.

By Nan (Nanook) on Tuesday, October 16, 2001 - 03:45 am:

It sounds like a yeast contam. Fizzling Honey Tek tells me you have it in your jars too probably. Yeast in jars is not really a visible contam, mycelia simply refuses to colonize even tho the substrate looks normal. Under the sink is a bad place to incubate: contam central.

Skip honey tek, get everything clean, go straight PF tek using his syringes... And find a cleaner place to store them.

Posted by: glasshoppa Dec 01 02, 03:39 PM GMT
From the archives, per Nan:

The most common reasons jars stall: incubation temps rising and falling ... lack of moisture; yeast contam which is not visible to the eye.

More information please on this YEAST CONTAM! I've been having problems with slow/stalled growth, and I'm wondering if this could be my problem. Temps are right, no *visible* contams. What sterilization temps does it take to kill yeast spores? How common are they? At what stage would they most likely be introduced? Inoculation? Does it stink? How could I verify the presence of yeast?

Posted by: Nanook Dec 01 02, 05:00 PM GMT
Packing a PF jar too tight will also cause this problem.

Yeast contam is generally introduced after sterilization, yeast is not that hard to kill... Just a few minutes at 212 degrees will kill yeasts.

After yeasts get developed in substrate they will produce odor. Usually yeast contammed substrate simply does not colonize. So if the jars are not too tightly packed, and they have not dried out... yeast can be a suspect.

On another note... tape will stall jars. If you use tape, remove it and flip the jar to drain out the pooled CO2 which can stall them.

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