1) Substrate preparation.
The substrate is the mushroom's food. In cultivated mushrooms, we generally distinguish between compost or bed mushrooms (Button mushrooms, Blue-foot mushrooms, Shaggy Ink Cap, ...) and lignivorous mushrooms that decompose wood and more broadly ligno-cellulosic materials (Oyster mushrooms, shiitakes, King Trumpets, ...).
Oyster mushrooms, for example, can be cultivated on cereal straw or on wood (logs, chips, sawdust).
The substrate preparation includes possible grinding, mixing with different materials, moistening, and usually pasteurization/sterilization. This process eliminates some of the microorganisms naturally present in the substrate that would compete with the chosen mushroom.
Pasteurization is generally done by heat through soaking in water at 75° for 1 hour, for example, or by steam. It can also be done by soaking for 12 hours in a cold water bath with slaked lime. The sudden change in pH (10-12) will eliminate some competitors and create a more favorable environment for the development of oyster mushroom mycelium.
2) Inoculation.
Inoculation, or larding... Somewhat barbaric terms that simply mean the inoculation of the substrate. The seeds or the « mushroom spawn » generally consist of grains or sawdust colonized by mycelium.
The production of spawn is the most delicate step in mushroom cultivation because it requires very high standards of cleanliness and sterility. Spawn is therefore generally produced in laboratories that sell and offer different varieties.
Each producer has their own inoculation technique. The more seed you use, the lower the risk of contaminations. But by using less seed, you can make more substrate and harvest more mushrooms.
The more a substrate is suited to the mushroom and well pasteurized, the less mycelium will be needed. Conversely, a substrate that is poorly or not pasteurized significantly increases the risk of contamination. That is to say, the appearance of other microorganisms (bacteria, molds) and therefore the inoculation rate will be higher.
The inoculation rate is the ratio between the weight of wet mycelium used and the wet substrate. Thus, an inoculation rate ranging from 1-2% is counted under laboratory conditions to a rate of 20% for outdoor cultivation, for example.
3) Incubation
This is the stage where the mycelium colonizes the substrate. It goes from grains distributed in the substrate to the straw or wood sawdust. To do this, it will produce a multitude of enzymes specific to each variety and each substrate.
At this stage, its metabolism will release heat and produce CO2. The higher the inoculation rate, the faster the colonization and the lower the risk of contamination. Indoors, the optimal incubation temperature is between 20 and 25°C. In nature, it can be cooler, and the incubation period will then be extended.
Example: indoors at 22°C, oyster mushroom mycelium colonizes a straw substrate in about 2 weeks and a sawdust substrate in about 3 weeks.
4) Fruiting
Most mycelia produce their fruits ("mushrooms") following stress which can have different origins: temperature drop in autumn, physical stress when a branch falls to the ground or soil is trampled, attacks by bacteria or other organisms, complete colonization of the substrate, competition with other microorganisms, changes in light, oxygen level variations, etc.
Oyster mushrooms, for example, fruit automatically as soon as they have finished colonizing their substrate, whereas morels generally need a particular stress to trigger fruiting and the appearance of their coveted fruits.
Fruiting requires a very high humidity level for the mushrooms to develop properly.
5) The harvest
After the effort, the comfort. The number of harvests on a substrate depends on the variety, the substrate, and also the producer who decides whether to keep the substrate longer or not.
The productivity decreases with each harvest, so producers generally do 2 to 3 harvests on a substrate, but we have already produced up to 8 harvests on a wood sawdust substrate.
The quantity also varies depending on the variety, substrate, and producer, but it is estimated that oyster mushrooms generally yield between 15 and 25% fresh mushrooms compared to the initial wet substrate, over 2-3 harvests.