Here’s where it gets a bit Marvel Comics: a company called Kraig Biocraft Laboratories has, in fact, managed to genetically engineer traditional silkworms using spider silk gene sequences – but that approach didn’t work for Bolt Threads, since it still requires large-scale farming, which has its own sustainability problems. Another challenge presented itself in the fact that, unlike the silkworm, which can be domesticated and farmed, spiders will eat one another in similar lab
conditions. The breakthrough finally came by incorporating a host that exists all around us: yeast.
Bolt Threads’ synthetic method relies on the planting, harvesting and replanting of sugar-producing plants – in short, it has bioengineered a yeast to produce a silk protein in large quantities. From there, the protein is spun into fibres and then knitted into Microsilk, its signature fabric. Compare this renewable process to polyesters, which are made from petroleum derivatives. Currently, more than 60 per cent of textiles are made that way.
So why isn’t every designer and brand using Microsilk? As anyone who has ever tried to brew their own beer or make their own bread can attest, many things can go wrong in the fermentation process, from subtle temperature changes to fluctuating pH levels. And when you’re talking about scaling up, these variables become even more volatile. So, the next step for Bolt Threads is to translate its process to fermentation vessels large enough to be able to create sufficient volumes of protein fibres. But what they have produced so far has gone down very well indeed. In 2017, the firm partnered with sustainability pioneer Stella McCartney to produce a gold Microsilk shift dress for the Museum of Modern Art’s exhibition, Items: Is Fashion Modern?. Bolt Threads CEO, Widmaier, said at the time, ‘We’re excited to leverage our signature protein-based yarn, inspired by spider silk, within upcoming Stella McCartney collections. As our partnership develops, our teams are eager to collaborate on additional technologies and textiles, and explore the possibilities of innovation by working together.’
And innovate they have, by adding mushrooms into the mix – and more specifically, their subterranean bacterial colony, known as mycelium. In 2017, Bolt Threads partnered with Ecovative Design, a startup that creates a faux leather which it calls Mylo. By developing mycelium cells to assemble into a textile, Mylo can be grown in a matter of days and is ultimately biodegradable. According to McCartney, who is working with the fabric, it looks and feels like handcrafted leather, and every sheet yields unique variations, making each product one of a kind.
What makes these sustainable fabrics so exciting is that they are really just the tip of the biotech iceberg. From squid beaks to dragonfly wings, nature has an abundance of super-materials which can all, in theory, be bioengineered to form materials that could dramatically reduce the environmental impact of the fashion and textile industries. That’s an idea that could literally grow on us.