Bolt Threads: the silicon valley start-up making sustainable fabric from spiders and mushrooms

Silk from spiders and leather from mushrooms... Chloe Street speaks to Bolt Threads CEO Dan Widmaier about the innovative materials set to change fashion for the better, forever
Bolt Threads
Chloe Street6 April 2020

When a spider gets scared and drops down on a line, it releases a liquid stored in a little gland inside its abdomen that is spun as its dropping, instantly turning into a fibre.

This fibre, known as spider silk, has high tensile strength, elasticity, durability, and softness and, weight for weight, is stronger than any steel. It’s a material that’s excellent for web construction and ensconcing prey but also one that, when mass-produced, has myriad commercial uses: from surgical implements to skincare formulations and, perhaps most significantly, garment manufacture.

The tricky bit is producing it at scale. Farming arachnids, whose cannibal natures become evident when they are left alone together in cages, is not possible and therefore scientists have spent the last 50 years trying to create a spider silk mimic in the lab - a largely fruitless labour. Until recently.

Venture-backed Californian biotech start-up Bolt Threads has successfully developed technology to replicate the spider’s amazing silk-producing process sustainably and in a way that’s industrially scalable.

The company, whose headquarters are in Emeryville, develops proteins inspired by these natural silks which they then produce in large quantities through a process of fermentation, before isolating and purifying the silk protein, then spinning it into fibres, similar to fibres like rayon and acrylic. The resulting fabric, which Bolt Threads calls Microsilk, is a vegan alternative to silkworm silk that’s not only produced with less environmental impact than traditional textile manufacturing, but also has the potential to biodegrade at the end of its useful life.

Dan Widmaeir, Bolt Threads CEO

“We spent a lot of time initially with spiders under a microscope spinning silk, trying to work out what they are doing,” says Bolt Threads CEO Dan Widmaier, who co-founded the company with two fellow PhD scientists David Breslauer (who has a Bioengineering PhD and is now Chief Scientific Officer) and Ethan Mirsky (who has a PhD in Biophysics and is now Head of Strategy) in 2009.

The idea for the company came from the research Widmaier had done as part of his PhD in Chemical Biology at the University of California, San Francisco, where his professor had tasked him with the well-trodden challenge of trying to make the spider silk protein. “It was only 10 per cent of my studies but it turned out to be a very hard problem that was very engaging,” says Widmaier, “and as someone who’s personally very passionate about environmental issues, it felt like it had a lot of application for both need in an industry, as well as environmental good.”

At that time, most scientists were focussed on the use of the silk in medical devices (for which it’s a great material as the body doesn’t treat it as an allergen, and therefore doesn’t reject it), however Widmaier had already envisioned its wider applications in consumer products, and was excited to start on the path to production. “I graduated on a Friday and on Monday I was the first full time employee,” he recalls. “I had an empty lab bench and a box full of live spiders.”

Stella McCartney dress made using Microsilk, unveiled at the New York MOMA in 2017
Bolt Threads

The first 15 months were spent analysing the spiders which, much to the chagrin of the other scientists with whom Bolt Threads shared a lab, had to be let loose in order to make webs freely. “We would just feed them by throwing bugs in the web and what have you… our lab neighbours really didn’t like us.” Progress was slow, but eight years of study and 1000 different breeds of spider later and Bolt Threads had a working arachnid thread.

In 2017, Bolt bought New York-based lifestyle and clothing brand Best Made Co. to bring its materials directly to consumers through limited-edition runs and collaborations. In March 2017 it launched its first commercial Microsilk product, a limited edition run of £250 silk ties that sold out almost instantly. “It’s such a new technology, and has presumably a lot of promise to be a physical thing that people touch, feel, wear… but no one had ever demonstrated that before,” he says. “So we thought we are not just going to show something, we are going to sell something. The idea was to get the world to understand the technology was real and could work.”

Later that year Bolt Threads also unveiled its first collaboration with designer Stella McCartney, a dress made with Microsilk fabric, unveiled at the New York Museum of Modern Art’s exhibition titled, “Is Fashion Modern?” and last summer the collaborative partnership produced its second prototype, a biodegradable tennis dress, created with a Microsilk and cellulose blend. These prototypes have proven the possible commercial functionality of spider silk, but for now it remains significantly more expensive than its traditional silk counterpart. “Now we need to scale it,” says Widmaier, “we need to make it cheaper better, faster stronger… but it can work.”

The Bolt Threads labs tested approximately 1000 different species of mushroom
Bolt Threads

While there might still be a wait before Microsilk hits the fashion mainstream, the company has another biomaterial invention up its sleeve. It’s one that Bolt is already producing in massive quantities and could well turn the leather industry on its head. It’s called Mylo, and it’s made from mushrooms.

In 2016, Widmaier and his team developed a synthetic leather-like biomaterial made from mycelium, a network of thread-like cells that forms the underground structure of mushrooms. To make the Mylo, Bolt engineered the root systems of mushrooms to grow into an interconnected 3D network, which the scientists then process, tan, and dye into a finished leather-like material. Not only does the process take less time and use less resources than traditional or synthetic leather production, but Bolt supports traditional mushroom farmers and tanneries whose business is dwindling, teaching them to grow and treat Mylo instead. The final product is soft, durable, and looks and feels remarkably like traditional leather.

A sample of the Mylo leather
Bolt Threads

In April 2018, Stella McCartney created a prototype version of her Falabella bag using Mylo, unveiled at the “Fashioned from Nature” exhibition at the Victoria & Albert Museum in London. The first commercially available product made with Mylo debuted later that year when Bolt collaborated with Portland-based bag brand Chester Wallace to launch the Mylo Driver Bag, sold via Kickstarter. In March 2019, Stella McCartney surprised Bolt by debuting a one-of-a-kind mini pouch she made using Mylo, alongside a series of garments she had made using Microsilk at Paris Fashion Week.

A Stella McCartney bag made with Mylo
Bolt Threads

And Stella is far from the only fashion house to have shown interest. In fact, given the huge number of brands making products using real and synthetic leathers, Mylo is, according to Widmaier, already in “huge demand” given the burden that synthetic leathers and livestock-based products have on the environment. While Bolt’s fashion partners as yet remain undisclosed, Widmaier does reveal the company is on track to scale to a million square feet of factory capacity to make Mylo this year, and is prepared to go “well beyond that afterwards.” The first Mylo cloth is due to start rolling off the line this year, with mass-produced Mylo products set to be shoppable later this year or early next (depending, of course, on how the current coronavirus crisis pans out).

The Mylo Driver Bag by Bolt Threads
Bolt Threads

Despite having collaborated on these prototypes, Widmaier assures Bolt Threads has no intentions to become an apparel company. “We want to impact sustainability on a global scale,” says Widmaeir. “So we want the brands who are out there that people already love to use our materials to make their clothes instead of other stuff. We are happy to go out and demonstrate that it works, that consumers like it, but long term we don’t intend to produce garments.”

In fact, targeting the 2.5 trillion dollar fashion industry was simply a pragmatic choice for a science-based enterprise determined to make a positive environmental impact. “Where you tend to see things happen faster in the world is where you see consumer opinion has shifted and pulled things along faster,” explains Widmaier. “Consumer product is the one place you see that happen… So going into fashion made sense. We didn’t know a lot about it, we had to learn, but I think we all said that anyone who’s smart enough (slash dumb enough) to do a PhD in science then spend six years doing more university, has to love learning. And you have to be good at it. So it didn’t frighten us to have to go learn something new, it excited us.”

While the size of the fashion industry is clearly attractive, is Widmaier optimistic about its ability to employ better practices and transition into a more sustainable future I wonder? “I am very, very optimistic. I wouldn’t be doing this if I wasn’t… And the reason I’m optimistic is because at the end of the day, we all report to the same customer. At the end of the day the consumer decides what we are going to do…” One of the company’s guiding principles, he says, is that as the visible impacts of climate change – things that you experience as an individual on a day-by-day basis – happen more frequently, and we as a society notice them and connect them to climate, we are going to demand solutions. And it will happen en masse. “And if consumers demand solutions, whether you’re me supplying raw materials or a brand supplying finished product, we have to listen.”

“And its already happening,” he continues. “We are on this inevitable path – bad things will happen along the way: more forest fires, more bad hurricanes… we baked that pie ten years ago – but I think people are waking up to it and we may look back in 20 years and say fashion is the thing that began to make consumers change their mind, and showed them it was possible, that then drove the change across society that we needed.”

The Mylo Driver Bag, Bolt Threads
Bolt Threads

Whether fashion can have the power to incite such a seismic pan-industry shift remains to be seen; but one thing that is becoming increasingly clear is that when the world emerges from this unprecedented period of turmoil, the existence and future of entire industries will be called into question. And as one of the world’s most polluting, fashion will surely be one of them. A 2017 report from the Ellen MacArthur Foundation found that textile production alone emits 1.2 billion tonnes of greenhouse gases, while a garbage truck worth of clothing gets dumped in the landfill every second. Virus or no virus, to maintain the status quo has become untenable.

More than ever before we need companies that deliver innovative, beautiful and highly functional products made with renewable and biodegradable materials using sustainable practices. Bolt Threads, who have calmly and quietly grown from a group of three scientists with a box of spiders to a company that nowadays employs over 100 people and has secured over $200 million worth of investor capital, could well be one of them.

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