Picture of Cook your own microbial growth plates
The goal of this hands-on project was to make and validate microbial growth plates with ingredients and tools commonly found in a kitchen.

I performed this with my first year bachelor students in dietetics and nutrition.

By making these plates the students get a better understanding of what microbial organisms need as an energy and nutrient source.
Also will they have to perform standard methodes and practices (working sterile, waste managment,...) applied to microbiology labs in order to achieve the goal.
By interpreting the results students will learn to analyze and be critical. They will also learn a bit more about differential (growth) behaviour of microbes.
By using common kitchen ingredients and tools, microbiology is taken out of the lab and placed into the dietician's world. I hoped by doing this microbiology would become less abstract and more fun to them.

I tried this project with bachelor students in dietetics and nutrition, but I guess it is suited for other students as well.
This is a low-cost project that can be performed in any basic kitchen.
My students were enthousiastic, it was fun to do!

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Step 1: Ingredients

Picture of Ingredients
dry yeast.jpeg
We decided to make a microbial growth plate based on the growth plate YPD routinely used to grow yeast in research labs.
YPD consists of 1% yeast extract, 2% peptone and 2% glucose.
Therefore we used 1% dry yeast, 3% milk and 2% sugar in our growth medium.

As solidifying agent we used gelatin (10%) instead of agar.
We also added salt (0,9%) since we want to grow bacteria on our growth medium as well.

kdaugherty1 month ago
I have pulled yeast from beer multiple times. Your best bet though is to make a yeast starter first, than pull from the starter to the growth plates. Of course you have to use beers that have been bottle conditioned( bottle with yeast to carbonate it.)

Lots of tutorials from us beer makers if you look up making beer/yeast starters.
how about SBA? ;) Just kidding. thanks for the tutorial and I am planning on saving this for my future kids!!! First to try this with my 9 y.o. sister <3
drdan1522 years ago
Very cool...will help me to be more cultured...haha get it...culture.
waldosan2 years ago
i've been looking for a way to make petri dish medium at home, this process seems a lot easier than buying the actual agar and cooking it up. what i want to do is keep a running colony of penicillium. my hypothesis is that keeping a running colony will allow the penicillin made from the mold to be effective against newer strains of bacteria like staphylococcus.

i don't have a pressure cooker though, would it be possible to sterilize the jars in a regular boiling pot of water over the stove?

i also have a propane stove at my house so it seems like i could inoculate the dishes there in the presence of the flame however i was wondering what being in the presence of a flame actually does? does it just move the air away from where you're working or does it actually sterilize the air from the heat?

finally your method for getting yeast from the beer won't work because the alcohol in the beer has already killed off the yeast. it's shed it's mortal coil and now it's body adds a grainy flavor to the beer that it made.
EhBmicrobio (author)  waldosan2 years ago
Hi Waldosan,

I've a protocol for the isolation of Streptomyces from mud. Streptomyces is known to synthesis antibiotics as well. I tried it out last year with students, and it worked out fine. I'll try to post it later (busy period right now: exams).

If you don't have a pressure cooker, you can try the process called tyndallization. I've never tried it, but it would be great to know your experience if you decide to try it out!

The flame is necessary to create a sterile environment. This will prevent contamination with other micro-organisms.

I've already isolated yeast from Westmalle, but by using YPD plates. Though it didn't always work. Most of the yeast in the beer is indeed dead.
tyndallization seems like the best way to go for that thankyou, I'm guessing it could be done in a big pot, those big ones that can make a noodle salad for an army.

exams, i don't miss those i won't lie...

do we know if the same people who are allergic to penicillin are also allergic to the streptomyces antibiotic? or are there common cases of being allergic to one and the other?

this makes me want to get some of those immortal cells that they always use instead of human testing...