The fungus is grown in vats using glucose syrup as food. A fermentation vat is filled with the growth medium and then inoculated with the fungal spores. The F. venenatum culture respires aerobically, so for it to grow at an optimum rate, it is supplied with oxygen, and carbon dioxide is drawn from the vat. To make protein, nitrogen (in the form of ammonia) is added and vitamins and minerals are needed to support growth. The vat is kept at a constant temperature, also optimized for growth; the fungus can double its mass every five hours.
When the desired amount of mycoprotein has been created, the growth medium is drawn off from a tap at the bottom of the fermenter. The mycoprotein is separated and purified. It is a pale yellow solid with a faint taste of mushrooms. Different flavors and tastes can be added to the mycoprotein to add variety.
A reproducible mutation occurs after 1,000 to 1,200 hours of cultivation in F. venenatum which greatly reduces the hypha length in the organism, which is considered unfavorable for production. Under normal conditions, this mutant strain will rapidly displace the parent strain. Replacing ammonia with nitrate as the source of nitrogen, or supplementing ammonium cultures with peptone, prevents this mutant strain from overtaking the product but will still develop. Alternatively, the appearance of the mutant can be delayed by varying selection pressures such as nutrient concentrations or pH levels.