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From Spider-Infested Digs, U.S. Company Devises Way to Spin Silk—Sans the Spiders

June 29, 2015
by Chelsea Leu

In the beginning, David Breslauer’s office was infested with spiders—lurking in the corners, hunkered down on their webs, crawling up his arms. “I had one right above my desk, and it pooed on my computer like a pigeon,” he says. And these were large, long-legged beasties, too: Nephila clavipes, an orb-weaving species commonly used in scientific studies.

Which is, of course, exactly why they were roaming free. Breslauer, who got his bioengineering Ph.D. from UC Berkeley in 2010, is in the business of making silk—specifically, spider silk. He and his partners, two UC San Francisco Ph.D.s, have founded Bolt Threads, a company that is now making synthetic spider silk that’s chemically identical to the natural stuff, and they’ve built up an innovative process to produce it on an industrial scale. To pull this off, the three had to become intimately acquainted with the material they were trying to mimic. “We tried building spider cages, but these spiders were large, and they needed a lot of space to build their webs,” Breslauer says. So in 2011, their office became the cage. “I habituated to them surprisingly quickly,” he says, though the company later moved to its current headquarters in Emeryville.

David Breslauer

Spider silk, like all silk, is a type of protein. The material is highly valued not only for its famed strength but also because natural spider silk comes in a variety of forms. “Each spider spins about seven different types of silk,” Breslauer says. They produce an incredibly soft variety for egg wrapping; another type, called flagelliform silk, is incredibly stretchy like spandex. These varieties have evolved for spiders’ specific ecological needs, and also happen to be qualities we’d like in our clothing, too. (Spider silk Spanx, anyone?) Accordingly, scientists have been attempting to synthesize these silks for decades. But the process is surprisingly finicky, and no one’s come up with a good way to mimic it on a commercially viable scale.

Until now.

The techniques that Breslauer and his partners have developed allow them to tweak the process to create different types of silks—strong, stretchy, super soft. These threads, in the future, will go into creating truly designer clothing, bespoke down to the molecular level. “We tailor the amino acid sequences for the protein, we can add functional features into a silk fiber that you wouldn’t otherwise find, we get the performance benefits of all sorts of materials you find out there, but with a natural fiber,” Breslauer says. They’re hoping to have apparel products—clothing made from their fibers you can actually wear—out by 2016.

To create a custom fiber—say, a soft cashmere-like thread—Bolt’s scientists start by designing the protein they want to produce on a computer. Then, in the molecular biology lab, yeast is engineered to produce that protein, in thousands of tiny plastic wells that each represents a single experiment. Breslauer indicates what appears to be a giant petri dish speckled with beige dots—colonies of yeast. “There are millions of cells in that little dot, which we pick. Then, quite literally, we put a small sample like that in a vial,” he says. Then the yeast are transferred to the fermentation room to grow in glass vessels, nurtured on a steady diet of sugar, salt and water, and from there to hulking chrome tanks containing up to 300 liters of liquid.

After fermentation, silk protein sloshes around with yeast cells in an off-yellow slurry, which is centrifuged in a room called “recovery and separation.” The silk is then drawn out and purified. Breslauer pulls a canister of white powder out from a fridge, complete with a Bolt Threads sticker, and it looks a lot like whey protein. (Not a coincidence, he says. The same methods that are used to make edible protein powders industrially translate well to producing silk protein in large quantities.)

When dissolved, the powder forms a thick, molasses-like gel, which is then propelled through a metal disk dotted with tiny holes—a device called a spinneret, just like the ones in a spider’s abdomen. “It’s like a showerhead, or a Play-Doh spaghetti-making machine,” Breslauer says. The result is fine white thread: bona fide spider silk, no thanks to spiders.

The company’s eventual goal is to create custom, high-performance clothing for consumers, and their small design team in Portland is currently developing products for the textiles that will be woven from these fibers. Breslauer points out that the cloth produced by their process offers a variety of perks that regular textiles don’t. Since the fibers are chemically the same as those found in nature, they biodegrade, minimizing waste in the environment (unlike petroleum-derived synthetics like polyester or nylon, which can linger for years). Their process doesn’t require the natural resources that agricultural-based textiles like cotton use, and also doesn’t fall prey to inclement weather, bad harvests or other vagaries of nature.

“There’s a lot of sen­sa­tion­al­ism in the spider silk world. We wer­en’t go­ing to start talk­ing about ourselves un­til we felt like we could de­liv­er on our prom­ises.”

Breslauer is enthusiastic and highly articulate, perfect as the company’s idea guy. The three University of California–educated co-founders complement each other, he says, which made dividing up responsibilities easy. “Dan [Widmaier, the Bolt Threads CEO] had a natural inclination for business, and Ethan [Mirsky, VP of operations] had experience with which he could support Dan’s inclination,” he says. “I like making new things, discovering things, building things!” As chief scientific officer, Breslauer runs the R&D team, which develops new silks and protein polymers and engineers the yeast to produce these polymers. His role puts him in charge of the majority of the company’s nearly 50 employees, many of whom have science Ph.D.s of their own. “This is the sort of thing you could only do in the Bay Area,” he says.

Breslauer met Widmaier and Mirsky less than a decade ago, when all three were still graduate students. The two UCSF students were trying to produce silk protein, which Breslauer needed for his research on microfluidic devices that would convert protein into fiber. Eventually, they figured out that the technologies they had developed for their theses were useless on a commercial scale—“almost naïve,” Breslauer says. So they left academia together and set up shop in the private sector, determined to collaborate on something viable in the marketplace.

After the company incorporated in 2009, their first years were spent quietly building up their technology and expertise. “There’s a lot of sensationalism in the spider silk world,” Breslauer says. “We weren’t going to start talking about ourselves until we felt like we could deliver on our promises.” In order to eventually remove the spiders from the process they were developing, they first needed to become intimately acquainted with the types and mechanical properties of spider silk—which is where the spiders came in.

There’s none of that in the company’s current digs, a spotless, light-filled office in Emeryville. The only spider in sight is the eponymous one on the cover of Charlotte’s Web, which sits on a table in the Bolt Threads lobby among journals and trade magazines including Textile World, Textile Insight and Biopolymers.

That particular copy of Biopolymers is a special issue dedicated to silk and co-edited by Breslauer, who thought he would end up in academia. “I grew up with Berkeley practically in my household,” he says, and no wonder—his father is George Breslauer, Berkeley’s former executive vice chancellor and provost, who retired in 2013 after 42 years at Cal. But the younger Breslauer took a different path. “Dan and Ethan were actually the ones who convinced me to go into industry,” he says, “and I have not looked back.”

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