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Lab-Created ‘Spider Silk’ a Sustainable, Compostable Alternative to Single-Use Plastics

The artificial “silk” product is manufactured using plant-based, sustainable materials and can be composted by consumers.

(CN) — England-based researchers have developed a plant-based polymer material that mimics the durable properties of spider silk and that researchers believe could one day replace plastics in consumer goods, according to a study released Thursday.

The material created by researchers at the University of Cambridge in the U.K. is as strong as many plastic products used by consumers and was modeled after the molecular structure of spider silk, one of the strongest materials in the natural world.

Researchers developed an energy-efficient method of assembling plant proteins into a polymer film used to form various consumer goods to be marketed and sold by Xampla, a University of Cambridge spin-out company.

Xampla will launch this year with a range of capsules and sachets that could replace plastics in products such as used in dishwasher tablets and laundry detergent capsules. The final product can be composted at home by consumers, eliminating the need for industrial recycling methods required by other bioplastics.

The process can add color and water-resistant qualities to the material and is scalable to industry manufacturing levels, according to the study published Thursday in the journal Nature Communications.

Lead researcher Tuomas Knowles of Cambridge's Yusuf Hamied Department of Chemistry said in a statement released with the study that for years he’s examined the molecular structure of various proteins and why some are stronger than others despite weaker molecular bonds. 

"We normally investigate how functional protein interactions allow us to stay healthy and how irregular interactions are implicated in Alzheimer's disease," Knowles said. "It was a surprise to find our research could also address a big problem in sustainability: that of plastic pollution. We found that one of the key features that gives spider silk its strength is the hydrogen bonds are arranged regularly in space and at a very high density."

Replacing plastic requires working with polymers found in the natural world: polysaccharides and polypeptides.

The team of researchers replicated the strong, durable structure of spider silk using soy protein isolate, which contains polysaccharides and can be sustainably sourced as a by-product of soybean oil production.

An example of a replacement for single-use plastic in consumer products, produced by mimicking the properties of spider silk, one of the strongest materials in nature. (Credit: Xampla)

The challenge of working with cellulose and nanocellulose polysaccharides is cross linking them at the molecular level.

"Because all proteins are made of polypeptide chains, under the right conditions we can cause plant proteins to self-assemble just like spider silk," Knowles said. "In a spider, the silk protein is dissolved in an aqueous solution, which then assembles into an immensely strong fiber through a spinning process which requires very little energy."

Researchers solved this challenge by placing the plant proteins in a mixture of acetic acid and water to make them more soluble and then using ultrasonication and high temperatures to assemble stronger molecular bonds.

Study coauthor Marc Rodriguez Garcia said in the statement the team analyzed both self-assembly and self-organization mechanisms in plant proteins as part of developing the Xampla material.

"Other researchers have been working directly with silk materials as a plastic replacement, but they're still an animal product," Rodriguez Garcia said. "In a way we've come up with 'vegan spider silk' --- we've created the same material without the spider. The key breakthrough here is being able to control self-assembly, so we can now create high performance materials. There is a huge, huge issue of plastic pollution in the world, and we are in the fortunate position to be able to do something about it."

The strength of the new material comes from the arrangement of polypeptide chains. The process requires no molecular cross-linking which is typically facilitated by toxic, non-sustainable chemicals.

"This is the culmination of something we've been working on for over ten years, which is understanding how nature generates materials from proteins," Knowles said. "We didn't set out to solve a sustainability challenge --- we were motivated by curiosity as to how to create strong materials from weak interactions."

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