Bolt Threads

Bolt Threads was a biomaterials company founded in 2009 that used bioengineering and fermentation to produce fibers, powders and leather-like fabrics intended as replacements for synthetic and animal-derived raw materials. Its earliest work centered on Microsilk, a spider-silk-mimicking fiber made by inserting silk genes into yeast, fermenting the resulting protein and spinning it into fabric. Scaling bio-based spider silk for textiles proved difficult and costly, and Microsilk was never used in widely available consumer goods, prompting the company to redirect resources toward other biomaterials [3][4].

The company's later primary product was b-silk, subsequently marketed as Vegan Silk: a bioengineered protein ingredient positioned as an animal-free substitute for silicone and keratin in skincare, haircare and beauty formulations, produced by fermenting yeast carrying spider silk genes and then isolating and purifying the protein. Bolt sold the ingredient to beauty brands rather than to consumers, after briefly operating its own skincare line, Eighteen B. b-silk appeared in brands such as Vegamour sold at Sephora in the US, and Vegan Silk was used in the Goddess Maintenance hair-care line distributed in more than 100 international markets. Bolt reported holding 34 patents for b-silk out of 49 total, with 131 further applications pending, and estimated the silicone-elastomer market it targeted at $4 billion [3][4].

A third line, Mylo, was a leather alternative grown from mycelium — mushroom root structure — cultivated in vertical farms by combining spores with sawdust and organic material under controlled temperature and humidity. Bolt described Mylo as non-biodegradable but less water- and greenhouse-gas-intensive than livestock leather and growable in weeks. Mylo products from Lululemon and Stella McCartney reached the market, but the line was put on hold as the company concentrated on b-silk [3][4]. The company's website states that Bolt Threads, Inc. is no longer operating [0][1].

Founding story

Dan Widmaier, David Breslauer and Ethan Mirsky founded Bolt Threads in 2009 to produce artificial spider silk. Widmaier, who studied spider silk during a PhD program in chemistry and chemical biology at UCSF and kept an office of golden orb weaver spiders spinning webs in hula hoops, became CEO; Breslauer, with a PhD in bioengineering from UC Berkeley and UCSF, became chief technology officer. Mirsky subsequently left the company [4].

Business model

Bolt Threads manufactured biomaterial ingredients and materials and sold them business-to-business to consumer-products companies and brand partners, having moved away from an earlier attempt to sell finished consumer skincare under its own Eighteen B brand. Its customer base consisted of brands buying or testing bio-based materials and ingredients, which produced lumpier revenue than a scaled manufacturing or licensing model [3][4].

Revenue came from sales of biomaterial ingredients and materials to brand customers. Sacra estimated revenue of $346K in 2022, $3.4M in 2023, $1.4M in 2024 (a roughly 60% decline attributed to one concentrated customer reducing purchases) and $4.5M in 2025, with company guidance of $11M for 2026 [3].

Traction

Lululemon launched Mylo bags in early 2022 and Stella McCartney also brought Mylo products to market; b-silk reached shelves through brands such as Vegamour at Sephora in the US, and Vegan Silk powered the Goddess Maintenance hair-care line sold in more than 100 international markets. Estimated revenue moved from $346K in 2022 to $3.4M in 2023, $1.4M in 2024 and $4.5M in 2025 [3][4].

Latest developments

To address liquidity, the company raised $4.3M in gross proceeds from an August 2025 private placement, converted $1.7M of vendor payables into equity in September 2025, signed a $20.0M equity line of credit with Ascent Partners in September 2025 with a $1.5M draw in October 2025, and announced a proposed convertible-notes-and-warrants financing of up to $30.0M with Murchinson in December 2025. Nasdaq notified the company on 2025-12-31 that it would be delisted; trading was suspended on 2026-01-05, shares and warrants moved to OTC Pink under BSLK/BSLKW, and the board approved voluntary SEC deregistration. The corporate website now states the company is no longer operating [0][1][3].