Geoff Gadd, a professor of biology at the University of Dundee in Scotland, learned that when he puts the mold in a container with urea and manganese, a mineral called manganese carbonate will form around the spindly arms of the fungus.
The trick works because mold secretes the enzyme urease, which breaks down urea (a nitrogen-rich compound that’s commonly found in fertilizers and urine) into carbonate and ammonium. Carbonate is negatively charged and can bond with positively charged metals like manganese. And the ammonium? “That’s what they [the fungi] are eating,” Gadd tells me.
When this mass of mold and manganese carbonate is heated up, it’s transformed again into manganese oxide, which is a common ingredient in rechargeable batteries.
The resulting mass of manganese oxide retains the skeleton shape of the fungus. This is what it looks like this under an electron microscope — a bit like the petrified roots of a houseplant. It’s kinda cool.
Here’s an even closer look. Here you can see how the carbonate forms around an individual fiber of the fungus.
Once Gadd and his team were able to create the manganese oxide, they were curious whether it could be used in a practical application. Batteries came to mind. Manganese oxide is commonly used as the cathode in rechargeable lithium batteries (the type likely powering your cellphone).
In their paper recently published in Current Biology, they find their battery retained 90 percent of its charging capacities after 200 power-and-drain cycles. That’s comparable to the batteries you can buy on store shelves.
It’s a neat trick. But what’s the point?
Gadd stresses this is just a proof of a concept. “Someone asked me when we can buy fungal batteries on Amazon,” he says. “It’s going to be awhile.”
The bigger picture of Gadd’s work is about finding biological processes to clean up pollutants or accumulate trace amounts of elements in a usable form.
In other research, Gadd has used fungi to trap lead, a very toxic metal, in a safer mineral form. He’s also shown that mold can turn uranium into uranyl phosphate, which is less dangerous for humans and the environment. He’s currently working on ways to collect cobalt and selenium, rare and expensive metals, with biological processes as well.
“There have been world declines in metal and mineral resources, and many of these resources are in the hands of just a few countries,” Gadd says. “We have to be looking into ways of recycling or reclamation.”
And bread mold is a promising start.