Fungiculture

Fungiculture is the specialized practice of cultivating fungi, such as mushrooms. This process yields various essential products, including food, medicine, and construction materials.

While humans practice this for industry, the term also describes how animals like leafcutter ants and termites grow fungi. Unlike plants, which use photosynthesis to convert carbon dioxide into carbohydrates using sunlight, mushrooms derive all energy from their growth medium. This medium is called a substrate. Fungi require high humidity, often between 95% and 100%, and specific moisture levels in the substrate. They reproduce via spores rather than seeds. Because spores can easily be contaminated by airborne microorganisms, professional growers often use mycelium, which is an actively growing fungal culture, to start their crops.

To begin cultivation, growers perform inoculation. This involves placing mycelium onto a sterilized substrate, such as rye or millet grains. These inoculated grains are known as spawn. Spores can also be used for inoculation, but they are much more difficult to manage. Because they are easily contaminated, spores are typically handled only in laboratory settings using a laminar flow cabinet. Once the spawn is added, the mycelium begins to grow through the substrate. This process transforms raw natural ingredients into mushroom tissue, specifically a carbohydrate called chitin.

One traditional method of fungiculture is outdoor log inoculation. This technique has been used for hundreds of years and is still used today for species like shiitake and oyster mushrooms. For shiitake production, growers use hardwood logs, such as oak, American beech, or sugar maple. They avoid softwoods because the resin in those trees can inhibit fungal growth. The process involves drilling holes into 1-meter hardwood logs and filling them with shiitake mycelium. The holes are then sealed with hot wax. The logs are placed under a forest canopy to incubate for 12 to 15 months.

To trigger fruiting, or pinning, the logs are soaked in water for 24 hours. This method is seasonal and unpredictable, so it accounts for less than 5% of commercially sold mushrooms.

Modern commercial mushroom farming often occurs indoors using trays. This method was first developed in caves in France, which provided stable temperature and humidity. In the late 1800s, this technology reached the United Kingdom through quarrying near areas like Bath, Somerset. By the mid-twentieth century, large-scale production moved into purpose-built, windowless buildings. Indoor growing allows farmers to control light, temperature, and humidity while excluding pests. The most common commercial species is Agaricus bisporus, which includes button, crimini, and portobello mushrooms.

The cultivation of Agaricus bisporus involves six distinct stages. First is Phase I composting, which lasts 6 to 14 days to regulate water and nitrogen levels. Phase II involves further composting or pasteurization, a heat sterilization process that lasts about two hours to reduce harmful microbes. The third stage is spawning and growth, lasting 14 to 21 days, where the starter culture propagates through the substrate. Fourth is casing, which takes 13 to 20 days and involves adding a top dressing to the substrate to induce pinning. Fifth is the pinning stage, lasting 18 to 21 days, where recognizable mushroom shapes form. Finally, the cropping stage consists of repeated 7 to 10-day harvest cycles.

Pinning is considered the most difficult stage for a grower. It requires precise management of temperature, humidity, light, and carbon dioxide (CO2) levels. During the vegetative growth phase, mycelium is often sealed in a gas-resistant plastic barrier to trap CO2 produced by the growing fungus. To trigger the formation of primordia, or mushroom pins, the grower must reduce the CO2 concentration from about 0.08% to the ambient atmospheric level of 0.04%.

This change in the environment signals the mycelium to begin forming the actual mushroom structures.

Substrates used in fungiculture can include many different materials. Common bulk substrates include wood chips, sawdust, straw, manure, corncobs, and even recycled paper or coffee grounds. Oyster mushroom farming is expanding rapidly because it can use substrates like wheat, paddy straw, or used coffee grounds. This type of farming requires less space and can offer higher profit per unit than many other crops. However, growers must protect their crops from pests and diseases. For example, sciarid or phorid flies can lay eggs in the substrate, leading to maggot infestations. Bacteria and molds, such as Trichoderma green mold, can also cause significant crop losses if hygiene is poor.

Various fungi are cultivated for different global needs. Pleurotus species, which include oyster mushrooms, are the second most important mushrooms in world production, accounting for 25% of the total. Lentinus edodes, or shiitake, makes up 10% of world production and is widely grown in Japan, China, and South Korea. Other notable examples include the winter mushroom (Flammulina velutipes) and the fungus used to create mycoprotein for meat analogues. From large-scale industrial trays to small indoor kits, fungiculture remains a vital way to turn organic waste into valuable resources.