Biology

The domestication of cheese fungi

Fermented cheeses such as Camembert or blue cheeses such as Roquefort, base their flavor and texture on the mushrooms that grow in them. Although it sounds simple, it raises big questions for microbiologists.

Penicillium molds are usually used in the fermentation of this type of cheese, and yet when they are wild in nature they are toxic. The next question is, how come there are domesticated species of mushrooms used to make cheese?

In a study published in the journal mBio , the findings suggest how this step could have been taken, not only in fungi that aid in the production of cheeses, but also in other foods.

Rapidly Evolving Mushrooms

Microbiologists have found that the evolution of fungi from a wild strain to a domesticated strain is very rapid – just a few weeks. The discovery was accidental when they were studying a colony of Penicillium , a wild-type bluish fungus that spoils cheese and other foods. Its smell according to Wolfe (the principal investigator of the study) is very similar to that of a wet basement.

Over time, microbiologists noticed changes in some of the laboratory plates that contained this fungus. Before long, the foul-smelling, blue-colored fungus stopped producing toxins. The cultures lost their bluish hue and turned white. Even its smell had changed to fresh grass, becoming very similar to another Penicillium well known to cheese lovers: Penicillium cammberti , the Camembert cheese mushroom.

This fact aroused great curiosity and gave a new avenue to study. To study this evolution in real time, Wolfe (responsible for the study) and his collaborators collected mushrooms from a cheese cave in Vermont that had been colonized by wild Penicillium strains that were not suitable for food production.

For testing, they seeded this mold on lab plates with cottage cheese. In some plates the wild mold was grown alone and in others it was grown together with other microorganisms that compete with Penicillium in the colonization of the cheese.

After one week, the molds were blue-green and fuzzy, which would be expected in their normal development, unchanged in all tests. However, after three to four weeks, the plaques where the fungus was growing showed only changes in appearance.

The domestication of cheese fungi
The domestication of cheese fungi

After this step, the mold populations were transferred to new dishes containing curd cheese with the result that in 30-40% of the samples the mold looked increasingly like P. camemberti. In some cases it became whiter and smoother and in others less diffuse.

In cases where the fungus competed with more microorganisms, the wild strain did not evolve as quickly.

In follow-up analyzes, they tried to identify which genomic mutations had led to this rapid evolution, but no obvious cause was found.

This discovery therefore opens up new questions. If this mechanism is genetic or not, if there is something in the environment in which the cheese is grown that activates an epigenetic switch or how stable this modification is.

The origin of fermented foods

Researchers suspect that the microorganisms used in most fermented foods, including cheese, but also beer, wine, sake, and others, were inadvertently domesticated and developed different flavors and textures in reaction to cultivation in a food environment. .

Wolfe says his laboratory study suggests that wild strains could be intentionally domesticated to produce new types of artisanal foods, such as American cheeses: “The mushrooms used to make American camembert are French” (…) “But maybe Maybe we can go out and find wild strains, take them to the lab and tame them. We could have a new and diverse approach to making cheese in the United States. “

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