Mushrooms can be grown on several substrates. They use mycelia to colonize the substrate and degrade its biochemical components, then siphon away hydrolyzed organic compounds as nutrients.
Unlike plants, mushrooms cannot photosynthesize. But they can be cultivated from spores or tissue culture. A sterile mushroom lab is necessary for these operations, especially one directing a constant flow of HEPA-filtered air.
Substrate
The substrate is the material in which mushrooms grow. It can be anything from logs and stumps to compost and straw. It must be prepared for spore inoculation and contain the right mix of nutrients. Many mushroom cultivators use agriculture byproducts like wheat or rice straw, coffee grounds, sawdust and grain hulls to create their own custom blend of substrate. Once the substrate is ready, it must be pasteurized or sterilized to remove competing microorganisms, which can prevent fungi from taking root and growing.
When a spore lands on the substrate it germinates and forms hyphae. Hyphae are a network of branch-like structures that connect cells and transport materials across the substrate. When hyphae are fully mature they produce fruiting bodies. The fruiting stage is a thrilling episode in the mushroom life cycle. The previously invisible work of the mycelium culminates in the mushroom formation above the substrate surface. The mushrooms are then harvested.
Mushroom cultivation relies on the right combination of temperature, humidity and substrate to encourage the development of a healthy mycelium. The process involves a variety of techniques ranging from wild harvests to outdoor log inoculations to indoor trays and bags. Each technique carries a set of pros and cons.
The most important step in the process is substrate preparation. The mushroom cultivator must choose a substrate that is suitable for the desired species of mushrooms. Ideally, it will be made of a carbon-rich material that is compatible with the fungus. This material should also be available at a reasonable price, and it should be easy to transport and store.
Pasteurization is a popular method of substrate preparation because it reduces the risk of contamination from bacteria and other microorganisms. However, it does not completely eradicate other organisms, such as viruses, fungi and mold spores. These organisms can compete for water, nutrients and energy with mycelium and interfere with their growth.
To avoid contamination, some cultivators use a double-bagging technique. They use a clean bag to transport the substrate and a second bag that is inoculated with a mushroom-safe spore mixture, such as agar tissue or liquid culture. Once the spore mixture is inoculated, it can be transferred to the substrate and sealed for further development. This practice, known as through-spawning, significantly reduces the time it takes for a colony to establish itself.
Inoculation
The inoculation process is the step that starts the mushroom cultivation journey. The goal of the process is to get the mycelium, the root-like structure that enables mushrooms to grow, to colonize a substrate. Once the mycelium colonizes a substrate, it can produce fruiting bodies under the right conditions. This whole process can take up to a year.
There are several different methods of inoculation, but they all have the same basic steps. Spores or mycelium are injected into a pasteurized or sterile substrate. The mycelium then spreads out over the substrate, secreting digestive enzymes that break down the lignin, cellulose and hemicellulose of the substrate. The resulting product, called primordia, eventually enlarges and matures to become a mushroom. The mushroom then releases spores to start the process all over again.
To grow mushrooms successfully, it is important to have a clean culture. This means that the spawn must be sterile, as well as the substrate and inoculation tools. Using a laminar flow hood is one way to ensure that all preparations are sterile. This can be expensive for a beginner, but it more than pays for itself in contamination prevention and in time saved.
When starting out, the easiest way to get a pure culture is to purchase ready-to-inoculate spawn from a certified supplier. Once familiar with the process, however, it is recommended that each cultivator create their own sterile spawn. This is the most cost-effective way to cultivate mushrooms.
This involves creating a nutrient-rich liquid medium in a Petri dish and then inoculating it with spores or mycelium. The resulting spawn is then transferred to a grain substrate and allowed to colonize. Once the spawn is fully mature (denoted as G1) it can be used to inoculate a number of grain-filled jars. This will generate another generation of spawn that is then ready to inoculate bulk substrates like straw, wood or compost.
Aside from the challenges of a pure culture, a growing cultivator must also contend with environmental factors, including temperature, humidity, CO2, airflow and lighting. Mushroom cultivation is a complex endeavor that requires an experienced eye for detail in each step.
Growth
Mushroom cultivation is a fascinating and complex process. Ultimately, cultivators use mycelium (the fungal root-like structure) to promote mushroom fruiting, and to create an environment that allows mushrooms to grow. The cultivation process includes many steps, and each operation is different depending on the needs of the mushroom farmer. But the overall goal is to produce a quality product. The main steps of mushroom cultivation are substrate preparation, pasteurization/sterilization, sterile transfer / inoculation, fruiting, harvesting, disposal and cleaning. There are many methods and techniques for growing mushrooms, but most involve harnessing the growth of mycelium, a process that is similar to directing ocean currents.
Spores that land on a suitable surface will germinate to form hyphae. When two sexually compatible hyphae fuse together, they form dikaryotic mycelium, the root-like body of the fungus. The dikaryotic mycelium secretes digestive enzymes to break down its substrate, and, under the right environmental conditions, it will enlarge until it forms a fruiting body called a mushroom. Once a mushroom is mature, it will release its spores, and the cycle starts again.
Throughout the fruiting phase, mycelium growth should be regulated to slow down and redirect it towards fruit production. This is referred to as induction. Some common induction strategies include spraying the substrate with water, lowering temperatures, and decreasing nutrients.
The final step in mushroom cultivation is to harvest the mature mushrooms and process them for sale. The most common mushroom harvested is psilocybin-containing lion’s mane (L. edodes). Several processes are used to preserve mushrooms, including vacuum cooling, cold storage and freezing.
The growth process begins with preparing the substrate, which may be any material that will support spore germination and mycelium growth. Various treatments are available to prepare substrate, including pasteurization, sterilization, lime bath, peroxide bath and cold fermentation. The choice of substrate depends on the type of mushrooms to be grown, and beginner growers should purchase ready-made spawn from a supplier until they become familiar with the germination and cultivation process. Eventually, every mushroom cultivator should learn how to make their own spawn, and this will save them money in the long run.
Harvest
Mushroom cultivation involves a complex dance between humans and fungi, wherein cultivators use numerous techniques (known in the mycology community as “TEKs”) to harness the growth of mushroom mycelium, the nutrient-rich foundation that promotes fruiting bodies. Cultivators must master substrate preparation, pasteurization / sterilization, sterile transfers & inoculations, growth management, and harvesting.
When spores or tissue culture land on a nutrient-rich substrate, they germinate and form “hyphae.” If they are sexually compatible with one another, the hyphae fuse to become dikaryotic “primordia” that enlarge to create a mushroom cap. Once mature, the mushroom caps sporulate to release spores back into the environment, repeating the cycle. During this process, cleanliness is paramount – like stirring up a well-written mystery novel, the mushroom media must be thoroughly stirred to ensure that all of its ingredients are dissolved and distributed evenly.
