Bolt Threads Successfully Produces Usable Biotech Spider Silk From Yeast

Five years ago, the graduate students behind a secretive startup called Bolt Threads set out to replicate the unique chemical properties of spider silk, an almost magically flexible and durable material that’s in some ways as strong as steel. One of the first things they did was buy a batch of Nephila spiders—the common golden silk orb-weavers—from an insect dealer in Florida. Then they let the spiders spin their webs all over the company’s first office at the University of California at San Francisco. One day a well-known UCSF molecular biologist walked in, saw a spider hanging in a doorway, and ran away screaming.

Scientists, at least those who aren’t arachnophobes, have tried to mass-produce spider silk for decades with little success. Spiders are territorial and cannibalistic—try to farm them, and they end up eating each other. But scientists have long believed that if spiders would only cooperate, fabric made from their silk would be well-suited for use in military and medical equipment, like wound sutures or artificial tendons, as well as in high-performance athletic clothing and other garments.

Bolt Threads has ditched the live spiders but held on to this goal. The company has developed a synthetic alternative to spider silk by engineering proteins identical to the natural threads stretched across the nooks in your basement. It’s raised $40 million from Silicon Valley venture capital firms Foundation Capital, Formation 8, and Founders Fund to commercialize its technology and turn those proteins into fabric. “Over the past few decades, as clothing companies squeezed on price, they’ve taken the innovation out of apparel,” says Dan Widmaier, a graduate of the UCSF Ph.D. program in chemical biology and Bolt’s chief executive officer.

Widmaier and co-founders Ethan Mirsky, Bolt’s vice president for operations, and David Breslauer, its chief scientific officer, are genetically modifying yeast, single-cell organisms that convert simple carbohydrates to proteins through fermentation, and getting them to excrete silk-like proteins. “What would have been done in cells of spiders is now being done by yeast in our lab,” Widmaier says.

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