Cheese mould, a new sanitary sterilizer?

Since the days of the ancient Romans, humankind has relied on mould to craft pungent, tasty blue cheeses like roquefort, gorgonzola and stilton.

Now, researchers have harnessed that edible fungus, Penicillium roqueforti, to create a self-cleaning foil that contains an embedded mould that eats away at food spilled on it.

The product is still rudimentary – it took the mould two weeks to digest half a teaspoon of sugary broth.

But it is one of the first times scientists have combined living organisms and a material component. The researchers foresee complex future applications such as weaving toxin-producing mould into fabric to create a self-sterilizing surface.

The research team, from the Swiss Federal Institute of Technology in Zurich, has published its findings in the Jan. 3 issue of the journal Proceedings of the National Academy of Sciences of the United States of America.

The project’s inspiration was the French cheese camembert, said one of the researchers, Lukas Gerber.

A soft-ripened cheese, camembert has a white, downy rind – or as the research paper calls it, “a living, functional biomaterial.” The rind, which is inoculated with the Penicillium camemberti mould, acts both as a ripening agent and a protective surface against other micro-organisms.

“Now, we want to take such a function from a living body and incorporate it into an artificial material,” Mr. Gerber said in a telephone interview. “It’s the first time [people] have designed a flat surface combining these two domains, the plastic and the micro-organisms.”

The foil they created was like a three-layered sandwich, with two polymer films encasing a thin coating of gelatinous culture holding the fungi.

The layer at the bottom was made with polyvinyl chloride, the material used in plumbing pipes and fake leather. The fungi, suspended in an agar mixture, were spread on that layer, then covered by a porous polycarbonate plastic membrane.

The researchers analyzed two sizes of the self-cleaning material, one about the width of a dollar coin and the other as large as a sheet of letter paper. A sugary broth made from potatoes was dropped on the samples. Within 14 days, the fungi consumed the spill until the sugar dropped “below detection limit,” Mr. Gerber said.

“That was cool; that was what we expected.”

Once the food was consumed, the fungi switched to a dormant state until another spill activated them.

As long as the material was kept from severely drying, the Swiss Federal Institute of Technology mould remained active, even after the foil was rubbed with alcohol hand disinfectant or scrubbed with dishwashing soap.

This showed that the material had a shelf life and might survive standard hospital washing routines.

The research opens the door to future applications that combine the benefits of micro-organisms with flat surface materials, Mr. Gerber said. For example, penicillin-producing fungi could be used to create antibacterial fabric that would generate antibiotics only in the presence of germs. Or large surfaces such as skyscraper facades could be coated with algae, which transform carbon dioxide to oxygen, to improve air quality.

“We wanted to show how easy it is to combine micro-organisms and polymer science,” Mr. Gerber said.