Growing Agar

The advantages of knowing how to go around nutrient agar are immense, and knowing how to prepare your nutrient agar will help you grow your mushroom efficiently. The knowledge of nutrient agar is necessary because it creates an enabling medium to save and propagate cultures. With this knowledge of agar, you’ll be able to make different types of spawn and other liquid cultures. This article will provide you with an explicit way of understanding how to prepare agar cultures for home and other small-scale production of mushrooms.


Although different recipes are in availability for the preparation of agar mix, they still follow the same procedures. These recipes include Potato dextrose agar PDA, Dog Food Agar DFA, and Malt Yeast Agar MYA. Your agar becomes more nutritious when you add some amount of food-rich ingredients to it, and in that way, your mushrooms' yield will turn out fine.

For every 1L of water your requirement for mix up:

  • 20g agar
  • 20g extract of malt, most used is barley
  • 2g of nutritional yeast

The truth is that finding local agar might prove a bit difficult, but online agar sources are there on your phones. You will also find some groceries that sell agar blocks which after purchase you’ll need to first grind before you can use it for your mix. For malt extract, you can check your local breweries while for the nutritional yeasts, visit some of the grocery stores that sell organic ingredients. To make your work easier, you can also go for an already mixed Malt Extract Agar and just add it to water. You’re also free to modify the mixture anyhow you want it, but take care not to add more than necessary water. You can use the following as directions:

1L of water for about 33-35 Petri dishes.


For your mixing, get hot tap water, don’t use cold water for your mixing. This is important because cold water will make your dry ingredients float immediately when you pour them inside the water, and this will make it difficult for you to properly mix them. Sterilizing your agar mix for some 45 minutes is also advised so that your mixture will be free from all contaminants. For an effective sterilization process and pouring, a whisky bottle that has a lid is recommended, and you achieve this by driving a hole on the lid. The hole acts as a filter which allows the agar to get access to sterile gas to cool down after sterilization. The lid should be covered with tin foil before placing it in the pressure cooker.

The major challenge sterilizing your agar inside a pressure cooker poses is that if care isn’t taken, everything could get boiled up. This happens when the water that you have outside the sterilizing bottle cools off before the one inside does, this makes the agar boil beyond the required level which could be bad for your agar.  But you can surmount this mountain by making sure your pressure cooker has more than enough water, which will help the cooling-off rate. For better results, place the agar bottle within the same level as the surrounding water in the pressure cooker. With this method, you’ll avoid the unpalatable boiling over.


Cooling off your agar after sterilization is very necessary, this will allow you to be able to work on it. But make sure you also don’t allow it to over cool, it still has to remain warm so a stop can maintain its liquid form. Cooling down shouldn’t take more than a few hours. You can use those hours of cooling down to put the place you intend to place your plates in order. You also need to adequately sterilize that area very well, remember you’re working with agar. Eliminate every potential agent of contamination that could put your entire mushroom growing system in jeopardy. Your breath or fingernails need to be seen as potential contaminants, in the light of this, you’ll be very careful when handling your materials. So ensure you wear things that will prevent your hands and breath or any other contaminants from getting to your Petri dishes and other sensitive parts of your growing project. Encourage wearing of face masks and other personal protective equipment.

It’s more assured to use either SAB known as a still air box or laminar flow hood. to prevent contamination. The latter is much better to use in case you want an environment that’s free of contaminants. However, without the use of either of these two, you can be sure that your plates are not in any way secure. SAB means a lid with holes driven on it. Everything that enters this SAB must be sterile and the inside of the SAB itself must have been cleaned with alcohol. A flow hood can be used by first turning the system on before you introduce all that you want to put inside. This helps to eliminate anything that could potentially harm your project. Also, clean its surface with alcohol and set the system in place.


The next step to carry out is to begin to stack the plates inside your SAB or flow hood to make sure you maintain sterility while doing this. Your best option of material to use for this arrangement could be Petri dishes. I said this because they usually come in a kind of pre-sterilized form. These disposable Petri dishes should be cleaned very well before you cut the bag open. Afterward, put them inside in about 4 stacks. Next is to open the lid after you must have taken the tinfoil away from the agar bottle. A laminar flow hood would require you to first make sure that the mouth of the bottle is exactly in the flow hood. Begin to pour the dishes into the flow hood in a rhythmic manner. Add sufficient agar to fill up the base of the dish. After you’ve poured in the agar, don’t immediately close the lid, leave it open for some while. It’s paramount that you don’t allow your hand to enter into the dish, this is because your hand could harbor agents that can be potential contaminants.

Leaving your dishes to cool down after pouring them is recommended. Your flow hood should be left on while cooling, thus preventing your system from coming in contact with diets and also aiding fast cooling.


The overall cooling and solidification processes shouldn’t last for more than 1 hour, after which you start to see condensed portions of your dishes on the top of your plates. When this comes up, don’t be in despair, everything is under control because they’ll eventually disappear after some while. When you get to this point, you can either choose to use them to prepare your agar work or probably keep them for later use. Remember contamination can happen at any time, so endeavor to seal the edges up. What works best here is laboratory-made parafilm. This parafilm helps your agar to breathe, and at the same time prevents it from contaminating agents. Just get about a 3-5 inches parafilm, peel, and stretch it over your Petri dishes, enough that it would cover the entire plate. Then your agar is ready for storage without any hitch.

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