Introduction: Preparing Agar Petri Dishes - for Growing Mycelium

Hello Fellow Scientists, or amateur scientists in my case.

I am experimenting with growing mycelium (a mushroom material) which you can see here , and I am pretending to be a scientist by developing better ways to control the growth of such an exciting material. I have read a lot about liquid cultures so I decided to grow some mycelium in petri dishes in a very basic way as the first step to grow the liquid culture (hopefully I can upload that when I have successfully made it).

You will need:

A Glass jar

Electric scales

Pressure cooker or a large pan with lid - the latter will take longer

Petri Dishes

Sharp knife


Dry Yeast

Malt syrup


I am posting this from a very non-scientific stand point, I am not a scientist and I am sure there are lots of other people similar to me who want to try experiments but don't have all the equipment. This is a test to see if it will yield results without the very precise nature of a laboratory process, to help all the budding scientists.

Step 1: Measure the Ingredients

Measure out the ingredients to make 500ml, this will fill about 8 - 10 petri dishes, as follows, using the electric scales:

12g agar-agar

10g malt extract

1g dry yeast

500ml drinking water

Screw the lid on the jar and shake well to make sure all the ingredients have combines well, make sure the malt extract is diluted as it can get stuck to the jar, depending on what order you put the ingredients in - water first helps the extract not sticking.

Step 2: Sterilise

Now place the jar into the pressure cooker or the large pot with water to the 2/3 level of the jar.

Get the lid locked and put the cooker on a hotplate. Sterilise for 45 minutes, counting from the moment as the pressure gauge reaches its highest stage (for household pressure cookers). If you've got a professional pressure steriliser at your disposal sterilise at 121°C/ 250°F/ 15 psi/ 1.05 bar.

If you do not have a pressure cooker then you should boil the jar on the stove for around 2 hours.

When you have reached the correct time, remove the pot from the heat and let it cool.

Step 3: Fill Your Petri Dishes

When the jar has cooled down enough for you to hold it take it out of the pot and give it a good swirl to get the sediment from the bottom fully combined with the liquid. The surface you do this on should be clean and sterilised with alcohol spray.

Lay your petri dishes out, keeping the lids on until the last minute. One dish at a time, take the lid off and pour in the sterilised liquid until the dish is about 1/2 - 2/3 full, place the lid back on as quickly as possible.

Repeat with all the liquid and dishes.

Allow to cool in room temperature for around 2-3 hours or until the mixture has solidified.

Step 4: Adding Mushroom Chipping to Grow Mycelium

This is an additional step, ignore it if you already know what you want to do with the petri dishes which doesn't involve mycelium. Otherwise, this step explains how to add the mushroom to the dish to begin the growing process.

Take a sharp knife, to sterilise it hold it over an open flame until it goes red hot, of course be careful not to burn yourself or melt any not metal parts of your knife. Remember it is extremely hot for a little while after so do not touch it out of curiosity with bare skin, if you need to test if it has cooled then through a paper towel is best.

When cooled, take the mushroom and slice a few pieces of the stem into the dish, trying not to let any dust into the dish by only taking the lid off to place the piece on the mixture.

When you have the pieces on the agar mixture, put the lid back on and store the dishes in a warm and dark place, around 24 degrees should be good. Mycelium will start to form in a few days.