Fungi are eukaryotic organisms, including mushrooms, molds, and yeasts, that are genetically distinct from plants and animals. Unlike plants, fungi lack chlorophyll and cannot perform photosynthesis, making them heterotrophs that absorb nutrients from their environment. Their cell walls are composed of chitin, unlike the cellulose found in plant cell walls. Controlled cultivation requires meticulously managing the environment to encourage desired fungal growth while excluding contaminants.
Establishing a Controlled Environment
Contamination prevention is the most significant hurdle in successful fungal cultivation, as mold spores and bacteria are ubiquitous. Cultivating fungi requires a dedicated, clean workspace where airborne particles and microorganisms can be minimized. This clean space, often a still-air box or small room, prevents foreign spores from settling onto the nutrient-rich growth medium during preparation and inoculation.
All tools, containers, and work surfaces must be sterilized immediately before use to eliminate competing organisms. A 70% isopropyl alcohol solution disinfects non-porous surfaces and metal tools. Metal instruments, such as scalpels or tweezers, can also be heat-sterilized by briefly heating them until they are red hot, a process that incinerates microbes.
Temperature and airflow are other environmental factors that need regulation. While optimal incubation temperatures vary by species, 70–80°F (21–27°C) supports the growth of many common fungi. Minimizing air movement prevents drafts from introducing contaminants when the culture is briefly exposed to the air.
Preparing the Growth Medium
Fungi require carbon for energy and nitrogen, supplied by a nutrient-rich growth medium, or substrate. Commercial cultivation often utilizes complex, pre-mixed mediums like Potato Dextrose Agar (PDA) or Malt Extract Agar (MEA). The agar component solidifies the liquid nutrients, creating a stable surface for the fungal mycelium to colonize.
For simple home observation, a basic nutrient source can be prepared from common household items. A simple broth made from boiling vegetable scraps or a mixture of gelatin and sugar provides the necessary carbon and nitrogen compounds. This liquid medium must be heated sufficiently to kill existing microbial life.
The prepared solution is poured into containers and allowed to cool and solidify if using a gelling agent. The containers must be immediately sealed to maintain sterility until inoculation. The substrate must be moist but not saturated, as excessive water can lead to anaerobic conditions that inhibit fungal growth and encourage bacterial contamination.
Inoculation and Monitoring
Inoculation introduces the desired fungus onto the growth medium within the sterile workspace. The initial fungal material, known as spawn, can come from microscopic spores collected on a spore print, or a small piece of tissue from a mature fruiting body. A sterile tool, such as a needle or cotton swab, is used to gently transfer this material onto the solidified medium.
Once inoculated, the culture is moved to an incubation area where it grows undisturbed. Environmental conditions must maintain the species-specific temperature and humidity for the mycelium—the vegetative part of the fungus—to colonize the substrate. Mycelial growth typically appears as a white, cottony network spreading across the surface.
Monitoring involves observing the culture’s development. Observers should note the rate of growth, the color and texture of the mycelium, and the appearance of contamination. Contamination often presents as green, black, or pink fuzzy spots of mold. Most mycelium requires darkness during colonization, but some species need a light cycle later to trigger fruiting body formation.
Handling and Disposal
Working with cultivated fungi, particularly molds, requires specific precautions against potential health risks. Fungal spores can be highly allergenic, and some species produce mycotoxins that may be harmful if inhaled. Wearing personal protective equipment, including disposable gloves and a respirator-style face mask, minimizes direct contact and inhalation of spores during handling.
The primary safety concern arises at the end of the experiment or if contamination is observed. The entire culture, including the container and the growth medium, must be rendered biologically inactive before disposal. This involves sealing the contaminated container to prevent the release of spores into the air.
A simple method for deactivation is to treat the sealed culture with a strong disinfectant, such as a 10% bleach solution. The bleach should be introduced into the container and allowed to sit for several hours to sterilize the contents. The unit is then disposed of in household trash, ensuring cultivated organisms cannot spread spores outside the controlled environment.