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Scientists Engineer a New Mold-Burger

Petri dishes in gloved hands.
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Moldy burgers are more popular than ever.

Despite the unappealing origins of the fake meat, burgers derived from different fungi species have become supermarket staples in recent years thanks to rising consumer interest in environmental sustainability and meat-free lifestyles.

Now, a new pretend-patty is set to join these products on the shelves.

Using the genetic editing tool CRISPR-Cas9, researchers at the University of California, Berkeley, have engineered Aspergillus oryzae mold (also known as koji mold) to better resemble the color and flavor of beef.

The findings were published in Nature Communications.

Cheating meat

Koji mold is used in east Asia to ferment sweet potatoes into sake and soybeans into soy sauce and miso.

Given this existing function in human cuisine, the Berkeley researchers – and their colleagues from the Joint BioEnergy Institute, United States, and the Novo Nordisk Foundation Center for Biosustainability, Denmark – thought it would be a worthy
candidate for a new fungi-derived alternative meat.

The team used the novel CRISPR-Cas9 gene editing tool to first boost the mold’s production of heme – an iron-based molecule abundant in animal tissue that is partly responsible for the distinctive flavor of meat.

Next, to make the artificial burger that little bit healthier than the real thing, the team dialed up production of ergothioneine, an antioxidant found in fungi associated with cardiovascular health benefits.

After these changes, the once-white fungi turned red. After removing the excess water, a sample of the fungi mass was shaped into a patty, then fried into a “tempting-looking” burger.

Although the koji burger isn’t the first to be produced from edible fungi, the researchers behind the new “meat” say their design overcomes prior limitations of other products.

“Most current products are based on a small group of naturally occurring fungi, which have inherent limitations in their sensory appeal, nutritional value, and industrial performance,” Vayu Hill-Maini, a researcher at Berkely and co-author of the paper, told Technology Networks in an email.

“We sought to expand beyond this limited biodiversity through the use of synthetic biology, programming the molecular composition of the edible mycelium to better suit current human needs and preferences,” he added.

“We use sophisticated genetic tools to alter molecules in the biomass for sensory appeal (heme) or nutritional value (ergothioneine), demonstrating for the first time how contemporary biotechnology can be used to enhance fungal foods.”

Hill-Maini’s next objective is to make the koji fungi more appealing by tuning the genes that control the mold’s texture.

“We think that there’s a lot of room to explore texture by varying the fiber-like morphology of the cells,” he said in a statement. “So, we might be able to program the structure of the lot fibers to be longer which would give a more meat-like experience. And then we can think about boosting lipid composition for mouth feel and further nutrition.”

“I’m really excited about how can we further look at the fungus and tinker with its structure and metabolism for food.”

Vayu Hill-Maini was speaking to Leo Bear-McGuinness, Science Writer for Technology Networks.

Reference: Maini Rekdal V, van der Luijt CRB, Chen Y, et al. Edible mycelium bioengineered for enhanced nutritional value and sensory appeal using a modular synthetic biology toolkit. Nat. Commun. 2024. doi: 10.1038/s41467-024-46314-8