‘Monotub (Bulk) Method’ for growing mushrooms

Monotub (Bulk) Method: The monotub method is commonly used for larger-scale mushroom production. It involves preparing a larger quantity of substrate using ingredients like coir, vermiculite, and grain. The substrate is sterilized and then mixed with already prepared grain spawn. The mixture is placed into a large tub or container, known as a monotub, and allowed to colonize. Once colonization is complete, fruiting follows, with proper environmental conditions maintained.

‘Grain spawn’ acts as a nutrient-rich medium for the spores to germinate and form mycelium, which eventually leads to the formation of fruiting bodies—the mushrooms themselves.

The ‘substrate’ acts as a nourishing matrix, supporting the mycelium's development and ultimately giving rise to the flourishing, harvestable mushrooms we seek.

Here is a high level overview of the primary steps involved. Below this is the ingredient list and detailed steps - the full recipe:

Prepare the Grain Spawn:

  • Sterilize and inoculate the chosen grain with mushroom culture or spores using a pressure cooker and mason jars.

  • Allow the jars to incubate until fully colonized for a couple of weeks.

Prepare the Substrate (once jars are fully colonized):

  • Hydrate and prepare the substrate mixture using coir, vermiculite, and gypsum. This requires a cooler.

  • Layer the bottom of a plastic tub with substrate.

Inoculate with Grain Spawn:

  • Break up the colonized grain spawn from the jars into small pieces.

  • Mix the grain spawn into the substrate in the mono tub.

Substrate Colonization:

  • Move the tub to a location with indirect light, maintaining temperature typically around 70-75°F (21-24°C), with proper air exchange, and moisture levels. Regular spraying and an attentive eye are required for this step!

Fruiting:

  • Mushrooms begin to develop and grow.

  • Humidity must be maintained via regular spraying for this step!

Harvesting:

  • Harvest mature mushrooms by gently twisting or cutting them at the base.

Drying & Storage:

  • After harvesting, gently wipe the mushrooms base to remove any dirt or debris you don’t want to ingest.

  • Depending on your preference, you can dry the mushrooms using a food dehydrator or other drying methods.

  • If using a food dehydrator, set it to a low temperature (around 130-140°F or 55-60°C) and dry the mushrooms until they are cracker-dry.

  • This process typically takes several hours.

  • Properly dried mushrooms can be stored in an airtight container in a cool, dry place for long-term storage.

Ingredients for preparing the grain spawn:

  • 5 quart-sized mason jars

  • masking tape

  • aluminum foil

  • 200g Rye grain per quart jar (source from a health food store, Amazon, or farmer supply store - horse feed)

  • spore syringes (1 cc per 1 quart mason jar)

  • Alcohol disinfect wipes or similar

  • lighter

Steps for preparing the grain spawn:

  • Add the rye grain and 220ml water to each mason jar.

  • Secure tin foil like in the image secured with masking tape. You will have 4 inoculate sites for even mycelium growth.

  • Pressure cook at 15 PSI for 90 minutes, then let cool completely at least overnight. Note: elevate the jars to avoid direct contact with the pressure cooker by user a rack or the lids from the pressure cooker. Add water as instructed by the pressure cooker manufacturer, usually a couple of inches to ensure the pressure cooker does not run dry.

  • When grain is completely cool, inoculate with the spore syringes. 1CC per quart jar.

    • NOTE: Contamination will ruin your work, be very careful here! Keep the jars in the pressure cooker and move them to a room with little airflow and do this step without the air conditioning running or any fans on. When ready, put on gloves and disinfect them with alcohol disinfect wipes. Disinfect the lighter. Wipe the jar lids with alcohol disinfect wipes. Attach the needle to the syringe. Use the lighter and heat the needle tip until it glows red. Let it cool for a second, then inject the spores in the jar. Before moving on to a new jar heat the needle tip again. After inoculation cover with fresh tape.

  • Incubate in a DARK, warm environment 75-80F undisturbed like in a closet for 2-3 weeks until the jars are white - completely mycellium growth. You are now ready for the substate and preparation of the monotub.