Bolt Threads and Spider Web Clothing

May 15. 2020. 6 mins read

They say clothes makes the man, a proverb that means you should dress to impress. In the Age of COVID-19, many of us have stopped wearing pants, but that doesn’t mean we’re not interested in some of the cool technology coalescing around clothing. You’ve probably read or seen some of the smart fabrics that can track your heart rate, respiration, and even your muscle development. Functional fabrics are particularly finding inspiration in the natural world, a science known as biomimicry. From sharkskin-inspired swimsuits to Velcro modeled on hooklike burs, companies are recreating and repurposing Mother Nature’s design for commercial products. And thanks to innovations in synthetic biology, startups like Bolt Threads are giving us spider web clothing without the spiders.

So What’s So Great About Spider Silk?

Spider silk has some amazing properties, such as being incredibly strong and lightweight. Take the Darwin’s Bark spider, for example, which was not discovered until 2009. It can create silk strands that extend up to 82 feet that are built out of the toughest biological material ever studied – about 10 times stronger than Kevlar. Then there’s the golden orb spider which weave’s a silk web of such strength that it can even catch birds. Over the years, researchers have been untangling the protein-based fiber’s structure down to the molecular level, leading to new insights and the potential for eventual commercial uses. 

Some of the far-out applications include harnessing spider webs for robotic muscles and even a real-world web-slinging contraption that the U.S. Navy is developing to ensnare enemy vessels. Near-term uses could include spider-sticky bandages in the biomedical industry and more durable alternatives to safety equipment like seatbelts and parachutes. The often-used comparison of a spider’s web being stronger than steel refers to tensile strength that’s as strong as steel at a fraction of the weight.

The problem is that it’s pretty hard to use actual spiders. You can’t exactly milk them like cows. There’s also the fact that they’re naturally territorial and cannibalistic, so any attempt to farm them would likely lead to an amount of arachnid carnage not seen since Bilbo Baggins visited Mirkwood Forest. So if you want to swing like Spiderman, you need to figure out a way to replicate the material in a lab.

Spinning Spider Webs with Yeast

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That brings us to Bolt Threads. Founded in 2009, the Emeryville, California startup has taken in a whopping $213 million in funding so far to create synthetic spider silk using genetically modified yeast cultures, which sounds nearly amazing as getting bitten by a radioactive spider. Investors include Fidelity, Baillie Gifford, Temasek Holdings, and Peter Thiel’s Founders Fund, among others.

Bolt Threads is using a form of synthetic biology, also called synbio, which applies engineering, design, and computer science principles to biology, usually at the cellular level. Often there is a high level of automation – and sometimes artificial intelligence – to replace the manual labor of yesterday’s laboratories. In one sense, synbio is about turning microorganisms like bacteria or yeast into biological machines, which is why we usually cover this topic under nanotechnology. In fact, we profiled Bolt Threads previously in our list of startups developing nano clothing technologies.

Like food companies producing certain kinds of alternative dairy and fake meat products using fermentation technology, Bold Threads inserts certain genes into yeast that feed on corn-based sugar to produce large quantities of silk proteins. But not to worry: The company’s overpriced Microsilk fibers are not genetically modified themselves. After fermentation is complete, the silk protein is purified from the yeast, and the remaining yeast cells are destroyed by the same methods used to pasteurize milk.

The company says its Microsilk offers not only better performance in terms of durability but it’s also eco-friendly. Depending on which pro-environment website you check, it can take hundreds, if not thousands, of gallons of water to produce one cotton T-shirt.

A Mushrooming Business

Bolt Threads appears to be positioning itself as some sort of eco-chic apparel maker. A few years ago, it debuted its first piece of spider web clothing – a synthetic silk tie that retailed in the neighborhood of $300. More recently, the company has unleashed its war chest of money to develop a non-animal leather product line that’s made from mycelium called Mylo, which can be produced in days versus years. The startup is able to control the mycelium’s growth conditions to produce a substrate that can be cured and tanned into a soft, supple material that looks and feels like leather.

Credit: Bolt Threads

Despite its millions in funding, Bolt Threads took to Kickstarter to help fund the project, offering a handbag to those who donated $400 or more. 

Super cool and all that, but those price points need to come way down if this will ever achieve more than just over-priced designer handbags for ESG types. We get it: The company is trying to showcase what you can do with these alternative materials in order to save the planet, in the same way other startups are going after the alternative protein market with microbes, fungi, and seaweed.

But then Bolt Threads went all Gwyneth Paltrow Goop on us last year when it introduced a new material called B-silk protein that it produces in the same way as Microsilk. As the company explained in a blog post: “Knowing the rich history of silk in biomedical engineering and tissue regeneration, we naturally wanted to explore whether our silk proteins might be beneficial in skincare.” Yes, saving the world one moisturizer at a time. Bolt Threads launched a whole new company, Eighteen B, named after the protein’s repeating molecular structure of 18 amino acid segments. The core ingredient in its lotions and potions is B-silk protein. Fast Company wrote a whole article on it, explaining how silk proteins act as a barrier to protect hair follicles and skin. If you’ve ever walked through a spider web in the woods, it doesn’t really feel that soothing to us.

An Expanding Spider-Verse

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In the same article on nano clothing technology, we also highlighted the work by Japanese startup Spiber. Founded way back in 2007, the company has amassed an equally impressive $246 million in funding and is a direct competitor to Bolt Threads. Spiber also uses fermentation technology to produce its Brewed Protein, a material that can be processed into a variety of forms, ranging from “delicate filament fibers with a silky sheen to spun yarns that boast features such as cashmere-like softness or the renowned thermal and moisture-wicking properties of wool.” It can also be processed into resins closely resembling tortoiseshell or animal horn for the Big Game Hunter in your household. In other words, the company has also gone down the runway of haute couture, enlisting famed Japanese fashion designers like Yuima Nakazato to feature Brewed Protein in their apparel lines. Spiber announced it will open a mass production facility in Thailand by next year with an annual capacity of several hundred tons.

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Yet a third company in the ever-expanding Spider-Verse of spider web clothing and cosmetics is AMSilk out of Germany. Founded in 2008, the company has raised more than $30 million, according to an article in Forbes. The startup also uses fermentation tech for its Biosteel fiber, but opts for using genetically modified E. coli bacteria for production. AMSilk actually sold off its cosmetics business last year to Givaudan, a Swiss manufacturer of flavors, fragrances, and cosmetic ingredients. That may signal that the company is focusing on developing different types of commercial and industrial materials based on its Biosteel fiber platform.

Credit: AMSilk

For instance, its synthetic silk polymers could be used as a coating for silicone breast implants to reduce inflammation after surgery. A couple of years ago, AMSilk inked a deal with Airbus to develop a new high-performance material that would use Biosteel fiber.

Update 05/12/2021: AMSilk has raised $35.26 million in funding to accelerate commercialization of its innovative and sustainable biotech silk materials. This brings the company’s total funding to $41.4 million to date.


We always knew that nanotechnology would lead to innovations in material science. We just never thought it would involve milking genetically tweaked yeast, bacteria, and silkworms to produce overpriced beanies and parkas. Still, we have hope that some of these companies will use their spidey powers for both profit and progress in areas like medical biotechnology and aerospace. Something has got to stick.


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