A Quick Update

I have had very little time to do experiments, so there’s nothing really new to post. I finally had a chance to make plates this past weekend so I am hoping to get some new things done soon. I had several plates go moldy after storing them in a plastic bag at room temperature, so I started keeping them in the fridge until ready to use.

I also plan on having some vials of DCY01 at the March DC Homebrewers’ meeting. Let me know if you are interested. Scratch that, I won’t be able to make it to the meeting.


7 thoughts on “A Quick Update

  1. bkyeast

    Try closing the plates immediately after pour and then letting them sit at room temp (covered) for a few days to dry up a bit. That’s what I started doing and I have about 0-2 our of 40-50 plates go moldy or grow some wild bug.
    I’ve been on a bit of a “break” as well – ran out of my old plates and making new ones turned into a disaster due to incredibly dirty agar I bought. Waiting for an agar that I know is good now…

    1. DC Yeast Lab Post author

      At the moment I’m pouring the plates prior to running them through the pressure cooker. I think this may be part of my problem, since I end up with some of the medium as liquid on the sides of the glass dishes, probably from the boil inside the cooker. This was the first time storing them upside down and inside a bag, so while that stuff eventually dripped down the sides and dried up it probably didn’t happen this time. It was pretty evident in this case with the mold growing in the gap between the lid and the plate while upside down.

      I’ve been meaning to try the standard approach. Perhaps the next time I make plates I will try that instead. I shied away from it worrying about airborne contamination but that may have backfired…

      Dirty agar? That sucks! I ended up buying more of the stuff from Whole Foods, since I find using just a bit more (maybe 10%) than is indicated works fine. I’m not sure I’m saving any money versus the lab-grade type but at least I can get it locally.

      1. bkyeast

        Oh man, I see. You’re not the first one who told me about this approach so I didn’t fall off the chair when I read this. Seriously the way plates are poured is you autoclave or pressure cook the agar in a flask or bottle or jar or something, let it cool to around 50*C and pour into the plates. Do it near a flame so that it creates an air flow that would prevent stuff floating in the air from falling into your agar. You open up your plate, pour, and close. After that, you open up the plate, go over it quickly with a flame (like blowtorch) to get rid of bubbles, and close. Normally in the lab you would leave them open to let them cool, but that’s because the medium is usually with antibiotics so bacteria that get on it will not live and mold will grow very slowly since they are then immediately refrigerated. Not to mention air filtration or some people do it in laminal flow hoods that prevent anything from falling into the cooling plates. Doing it at home, however, is not as easy so I find it best to just pour, close immediately and then let them dry off for 4-7 days to get rid of all that condensation plus let anything that may have fallen into the plate grow. Usually nothing grows, but once in a while some mold pops up and I just toss the plates into the trash. After that they can be stored in a sealed bad for weeks or in the fridge for months. I feel like I should do a “home-brew plate preparation” with pictures on my blog lol.

  2. DC Yeast Lab Post author

    Ha, I’m glad you are not injured due to my stupidity because that’s probably not the last time you’ll encounter it. It’s the result of the echo chamber effect, i.e. enough well-intentioned people recommend this method that eventually it becomes the “right” way to do it for a good number of people. It’s one of those things that seems to make good sense until you have problems like I did. So, yeah, if you had the time writing a post on the correct way to prepare plates would actually be quite good. There’s so much wrong info out there, and it’s something I’m very actively trying to avoid on my blog.

    I work on my plates flanked by two alcohol lamps burning quite hot so I should have decent upward air flow around the work area. I left a clean plate open for a few minutes between the lamps and after a week nothing had grown on it.

  3. bkyeast

    Good. Alcohol lamps or gas burners help. Having a hood, even without laminal flow, is also helpful (at least you can breathe easy 🙂 ). I guess I’ll do a how-to on home plate pouring.

  4. jaapie

    One advise is also to keep the plates in a ziplock bag, in tinfoil. In that way it keeps the condensation out. I was thinking of doing the same thing, writing a post about pouring plates at home 🙂 .

    What I do is steep some hops in the water I will use for the plates to get some antimicrobials in. Also lowering the pH helps. Another tip is if you have some old antibiotics lying around, to use them for these kind of experiments.. it wont help against the fungi, but you will keep bacteria at bay.

    1. DC Yeast Lab Post author

      Hi jaapie, thanks for the comment. I have seen your posts in the wild yeast thread on HBT. Very cool stuff there and on your blog. I admit I am very curious about your Pichia strain even though it sounds rather revolting 🙂

      The good news is I switched to making plates using the traditional method. I poured after the media had cooled down a bit and have not yet seen any sort of mold or bacterial contamination. I have barely had any time to work on this stuff but right now I am experimenting with two new strains. Plating them has been straightforward, and my media has not gotten mushy like in the past. Seems I am moving in the right direction. I had not thought of using tin foil to wrap them, so thanks for that tip.

      That’s cool about using antibiotics. I had wondered if something like that was possible, but then again I don’t really have any lying around. I also thought about lowering the pH, but not on the solid media. At some point I will make some acidified wort to see if I can pick up some sort of airborne yeast while hopefully skipping some of the enteric bacteria. Actually, I’ve been leaning towards using some leaves or inedible fruits from trees nearby, which would already have lots of bugs on them. Since I plan to isolate the bugs before using them I think I’d be OK even with inedible plants.


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