MicroSilk™ from Bolt Threads
Overview
Microsilk™ is a silk-like biosynthetic fiber made by the company Bolt Threads. Microsilk™ is made through a process of fermenting water, yeast and sugar with spider DNA.
Bolt Threads began by studying silk proteins spun by spiders to determine what gives them their incredible properties – including high tensile strength, elasticity, durability and softness. They then developed technology to replicate that process sustainably at large scale.
Microsilk™ is currently still in the R&D phase. Once the production processes are finalized, they will embark on life cycle analysis to determine the environmental impacts of our material, and utilizing the industry standard Higg Materials Sustainability Index, will be able to compare the results to dozens of other natural and synthetic materials. So far Microsilk™ fibers have only been used in prototype fashion products, including a limited edition collection of knit ties, collaboration with Stella McCartney – a dress for the Museum of Modern Art, and a limited edition beanie collection made of Microsilk™ blended with Rambouillet wool.
Benefits may include:
- Warmer than wool
- Lightweight
- Stronger than silk
Considered a renewable resource, the main input in the fiber-making process is sugar from plants that are grown, harvested and replanted.
How It’s Made
Tucker Bowe articulated the process perfectly in an article he wrote for Gear Patrol:
“Making synthetic spider silk involves several simple ingredients and very meticulous science. Sugar, water, and yeast cells infused with spider DNA are combined and left to ferment in large stainless-steel tanks. The mixture is then centrifuged, purified into a powder and mixed with a solvent. The resulting liquid silk protein, which looks like glue, is in the same natural state as the liquid protein that actual spiders extrude from their silk glands and then form into fiber.”
This liquid silk protein is then extracted through spinnerets and spun into fibers the same way fibers like acrylic and rayon are made.
No spiders are used at all in the process. Bolt Threads originally studied real spiders’ silk, to understand the relationship between the spiders’ DNA and the characteristics of the fibers they make. Today’s technology allows them to make those proteins without using spiders.
Microsilk® fibers do not contain any GMOs (genetically modified organisms). The production process does utilize genetically modified yeast. After fermentation is complete, the silk protein is separated from the yeast, and then the remaining yeast cells are destroyed by heat. There are no GMOs present in the final material. As they point out, this is the same technology that has been used for decades to safely produce cheese, along with insulin and many vaccines. The sugar that Bolt Threads uses in the fermentation process comes from genetically modified corn. At this time, all large fermentation facilities in the US use sugar from GMO corn because of the abundant supply. It is widely believed that large-scale fermentation will be possible with non-food crops known as cellulosic feedstock in the future. Bolt Threads claims commitment to being part of developing the solutions that will enable that future to be realized.
Suggested Reading
“Is Spider Silk the Performance Fabric of the Future?” By Tucker Bowe, Gear Patrol
“Stella McCartney Partners With Bolt Threads on Sustainable Material Development” By Jessica Iredale, WWD July 20, 2017
“This Striped Beanie Shows the Promise of Synthetic Spider Silk” By Elizabeth Stinson, Dec 7, 2017, Wired