Fusarium venenatum

What the fungus is

Fusarium venenatum is a filamentous fungus that grows as a fine, branching mycelium. The food ingredient is not the fungus as found in nature but mycoprotein, the edible biomass harvested from a controlled fermentation of the strain A3/5. Its strain name was once given as F. graminearum A3/5, which shows why the species name alone does not identify a production organism.

As a food, the biomass is a fibrous, meat-like protein. Its texture depends on the mycelium, and the production process is designed to keep the hyphae intact.

Development of the process

Rank Hovis McDougall set out in 1964 to develop a food from starch, and its screening programme selected the fungus. The first production used starch-based feedstock, which was a cereal-processing by-product. The Marlow Foods process later used glucose.

The fermenters came from earlier industrial work. The first production vessel, of about 40 cubic metres, was originally built by ICI to grow a bacterium for animal feed. Later plants were much larger, at about 155 cubic metres each.

How it is grown

Production runs as a continuous flow culture in an air-lift fermenter. The culture is run as a glucose-stat at a dilution rate of about 0.17 to 0.20 per hour, which keeps glucose in excess. Nitrogen is supplied as ammonia. Continuous culture gives much higher productivity than a batch process, which is why the process was built this way.

Highly branched colonial mutants arise during long runs and change the texture, making the product more friable. Fermentations are therefore usually ended within about 1000 hours of starting continuous flow.

Safety and mycotoxins

Some Fusarium species produce mycotoxins under nitrogen limitation, and certain F. venenatum strains, including the production strain A3/5/3, have done so under severe nitrogen limitation. The production conditions contain excess nutrients, and tests every 24 hours, sensitive to two parts per billion, have been negative. Producers and regulators rely on those tests rather than on the species name.

The safety of the mycoprotein product depends on the strain and on the production controls, not on the species alone. This page does not give a general safety verdict for the fungus outside the production process.

Notes

The sources differ on where the original soil isolate was found, and the page does not give a year for the isolation. The protein-yield comparisons and carbon footprint figures found in secondary material were not checked against primary studies and are not used here.