Wednesday, August 26, 2009

Making Plates and Slants

I realized the other day that I've got a couple of yeast samples hanging out in the fridge that I want to plate out and isolate. Since I recently used my last plate to isolate the Whitbread strain its time for me to make some more plates.

You can buy pre-poured plates at but I like to pour them myself. I mix up a solution of water, malt extract, and agar and boil it up. Be careful because this solution loves to boil over and I made a mess of the inside of my microwave the last time I did this :)

Right now I have plastic plates so I am not able to autoclave the plates and technically my agar mix is not sterile with boiling alone. The plates came pre-sterilized and so far I haven't had a problem with my boiled media into my pre-sterilized plates. At some point I would like to invest in some reusable and autoclavable glass plates.....

Once the boiled media has cooled down enough for me to handle the glassware I either pour or use a syringe to fill my plates. They gel up pretty quickly. I seal them up and will keep them out at room temperature for several days to a week to watch for any growth. If anything grows I know that I have some contamination. If they stay blank I bundle them away into the fridge for storage.

There's a lot of information about these procedures out there on the Internet. One of the sites that I found helpful was the BrewKaiser

I can't wait to get my new plates set up so I can add to the stable. One of my projects is to try and recover yeast from a 15 year old BarleyWine. I'm pretty interested to see what if anything has survived in there for so many years. If I do manage to recover anything it will also be interesting to see if it looks like I am getting a single isolate or more than one.....


  1. Have you tried malto goya? It is a malt drink that is basically unfermented beer. I hear it makes good starters and I bet it would work mixed with agar. Just alcohol and flame the top before opening.

  2. Interesting thought Scott. I would be worried about preservatives that they put in it to prevent fermentation in the bottle but if you could use it for starters I would think it would work as an agar plate nutrient. Maybe we should try this some time....

  3. used petri dishes are pretty cheap off eBay. I use a pressure canner as the poor man's autoclave.