Space & Innovation

The Future of Sustainable Fashion: Mushroom Leather and Synthetic Spider Silk

Bolt Threads is bringing sustainable materials out of the labs and onto the runways.

Bodysuit designed by Stella McCartney using Bolt Threads biofabricated silk. | Bolt Threads
Bodysuit designed by Stella McCartney using Bolt Threads biofabricated silk. | Bolt Threads

Ask any gathering of chemists and they'll tell you: Spiderwebs are weird. Made from chains of proteins, spider silk can exhibit tensile strength that is proportionately stronger than steel, yet they're highly stretchable and even edible.

Mushrooms are even weirder. On the cellular level, mushrooms are fundamentally different than other life forms and have unique medicinal properties. And they have their own classification that is neither plant nor animal.

A California-based company is finding novel applications for both mushrooms and spider silk by developing ecologically friendly textiles. If all goes well, the company, Bolt Threads, will soon be providing entirely news kinds of apparel for the 21st century.

Bolt Threads was launched in 2009 by chemist Dan Widmaier, building on his research at the University of California, San Francisco. The company's first bioengineered material, Microsilk, is a synthetic spider silk — without the spiders.

“We study silk proteins found in nature to determine what gives them their incredible properties and create Microsilk through bioengineering techniques,” Widmaier told Seeker.

Microsilk is designed to mimic a particular kind of spider silk known as dragline silk — the stuff spiders extrude to make their webs. The manufacturing process is surprisingly similar to brewing beer, Widmaier said.

“To create Microsilk, we wholly engineer and produce silk protein, primarily using the ingredients of sugar, yeast, and water,” he said. “We develop proteins inspired by natural silks by putting genes into yeast. From there, using our proprietary technology and a fermentation process, we can turn the protein into a fiber following a wet-spinning process.”

The Mylo Falabella | Bolt Threads

The fiber can then be built into silk strands that can be knitted or woven into apparel and other materials. In 2017, Bolt Threads debuted its first commercial products — a high-end silken necktie and a skullcap hat — in limited runs. The company also produced a one-off, gold-colored dress, in collaboration with designer Stella McCartney, which was shown at fashion shows last year. McCartney is currently presenting a new Bolt Threads prototype outfit at the London exhibit Fashioned from Nature.

Earlier this month, Bolt Threads announced a new partnership with New York startup Ecovative to manufacture Mylo, a synthetic leather made from mycelium, the underground root structure of mushrooms.

Under specific growing conditions, mycelium self-assembles into a supple material that looks and feels like animal leather, Widmaier said.

“We're currently growing Mylo in Ecovative's facilities in New York, as well as exploring additional facility options for continuing to scale up the process,” he said. “We're simultaneously working on process optimization at our labs in Emeryville (California).”

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The first Mylo handbags will go be available for pre-order in June through the company's website. Bolt Threads is also developing retail partnerships with Patagonia and the online retailer Best Made Co., which Bolt Threads acquired earlier this year.

The company is currently focusing on relatively high-end products — retail price for that limited run hat was around $200, and the necktie was $300. The company has yet to set a price for the Mylo handbags, but said it will be equivalent in cost to premium leather bags.

The ultimate goal, Widmaier said, is to ramp up production and gradually expand into several new lines of Microsilk and Mylo products at various price points. By making silk without spiders and leather without animals, Bolt Threads hopes to establish a new and sustainable approach to manufacturing apparel and other accessories.

“The textile industry at large hasn’t achieved major innovation in decades,” Widmaier said. “We hope to create innovative materials that are better for our planet.”