Black Agar - How to make activated carbon agar plates for mycology

Black Agar – How to Make Activated Carbon Agar Plates

What is ACMEA, AKA “Black Agar”?

Black Agar is a variation of Light Malt Extract Agar (LMEA) used in mushroom cultivation. By adding activated charcoal powder to the traditional LMEA mix, you get a darker, black growth medium. Many cultivators, including myself, prefer black agar because it seems to promote stronger and faster growth. However, these observations are anecdotal, and more research is needed to confirm this.

Black Agar is also known as Charcoal Agar, Dark Agar, or Activated Charcoal Agar, ACMEA.

Benefits of Black Agar

Black Agar offers several potential advantages in mushroom cultivation:

  • Visibility: The contrast between the black agar and white mycelium makes it easier to monitor growth.
  • Strength & Speed: Many cultivators, myself included, have observed seemingly stronger and faster mycelial growth on black agar. This could be due to the porous nature of activated charcoal, which provides more surface area for the mycelium to colonize.
  • Reduced Contamination: Anecdotally, black agar appears to have less contamination compared to traditional LMEA. This might be related to the presence of activated charcoal, which has known filtering and adsorption properties.

Ingredients

Ingredient Ratios

WaterAgarLMEACPlates
250 ml5 g7.5 g~1 g~10
500 ml10 g15 g~2 g~20
1000 ml20 g30 g~4 g~40
1500 ml30 g45 g~6 g~60
2000 ml40 g60 g~8 g~80

Step-by-Step Black Agar Preparation

Preparing Black Agar is similar to making Light Malt Extract Agar (LMEA), with the addition of activated charcoal powder. Here’s how to make 250ml of black agar.

How Long Will it Take?

  • Preparation: 10 mins
  • Cook time: 30 mins

Dry Ingredients

  • Measure out the dry ingredients using a digital scale:
    • 5g Agar-Agar
    • 7.5g Light Malt Extract (LME)
    • ~1g activated charcoal powder
  • Add these to a glass container.

Boiling Water

  • Measure out 250ml of boiled water and pour it into the container with the dry ingredients.

Dissolve

  • Stir until the dry ingredients are completely dissolved. Using a magnetic stirrer can help ensure a thorough mix.

Protect Lid

  • Secure a cap on the container and cover the top with foil to prevent steam from entering during pressure cooking.

Pressure Cooker

  • Place the mixture in a pressure cooker or autoclave. Seal the lid and begin cooking.
  • “You can place empty jars around the agar mixture to prevent it from tipping over.”

Cook at 15 PSI

  • Pressure cook the mixture for 30 minutes at 15 PSI.
  • Be mindful of overcooking, as the sugars in the malt extract can undergo Maillard reactions with the amino acids, potentially affecting the medium.

Depressurize

  • Once the time elapses, turn off the heat and allow the pressure cooker to return to zero PSI before opening the lid. When ready, remove the agar and place it in your work area.
  • “Don’t leave the agar in the pressure cooker for too long, or it will begin to solidify.”

Monitor Temperature

  • Allow the mixture to cool to around 115-125°F (46-52°C) before pouring. Use an infrared thermometer to monitor the temperature.
  • If it cools too much, it will begin to solidify.

Ready to Pour

  • Pour your mixture into petri dishes. Follow the sterilization protocol for this part. It’s a good idea to prep while the agar mixture is cooking.

Tips for Success with Black Agar

Handling Activated Charcoal Powder

  • Activated charcoal powder is very fine and can create a mess. Here’s how to manage it effectively:
    • Prepare your workspace: Lay down newspaper or a disposable tablecloth before handling the powder, as it can easily spread and stain surfaces.
    • Transfer to a plastic container: The powder typically comes in a bag, which can cause a cloud of thick black dust when opened. Consider transferring the powder into a container for easier and safer storage.

Other Tips

  • As with LMEA, pour your agar plates in a sterile environment and store them properly to minimize contamination risk.
  • Experiment with different amounts of activated charcoal to determine what works best for your specific strains.
  • While my observations and those of other cultivators suggest some advantages to using black agar, these remain largely anecdotal, and further research is needed.

Note: The ingredient ratios are the same as for LMEA, with the addition of activated charcoal powder. Start with 1 gram of activated charcoal per 100 ml of water, and adjust as necessary based on your observations.

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