Can this vegan spider silk replace single-use plastic?
Cambridge University researchers may have found a viable solution for single-use plastics: vegan spider silk. The new material is a synthetic polymer film that mimics the properties of spider silk, one of the strongest materials in nature. Due to its strength, the material could replace plastic in many common household products.
The vegan spider silk was created with a new approach of assembling vegetable proteins into materials that mimic silk on a molecular level. The energy-efficient process uses sustainable ingredients and results in a plastic-like, free-standing film that can be produced on an industrial scale. The material is also compostable, unlike other types of bioplastics that require industrial composting in order to break down.
A surprising finding
The researchers developed the material while researching something completely different: proteins and Alzheimer’s disease. Tuomas Knowles, a chemistry professor and senior researcher at Cambridge University, analyzed proteins to understand why proteins, in some cases, become malformed, leading to disease and health problems in humans.
“Typically, we study how functional protein interactions enable us to stay healthy and how irregular interactions are linked to Alzheimer’s disease,” Knowles said. “It was a surprise that our research could also address a major sustainability problem: that of plastic pollution.”
As part of their research, Knowles and his team became interested in why materials like spider silk are so strong when they have such weak molecular bonds, and they found that one of the key features that give spider silk their strength are the hydrogen bonds, which are arranged regularly in space and at a very high density. The team also investigated how this function can be replicated in other plant proteins. They were able to successfully recreate the structures of spider silk by using soy protein isolate, a protein with a completely different composition.
“Since all proteins are made up of polypeptide chains, under the right conditions we can get vegetable proteins to organize themselves like spider silk,” said Knowles. “In a spider, the silk protein is dissolved in an aqueous solution, which is then combined into an immensely strong fiber through a very low-energy spinning process.” The researchers used soy protein isolate as a test plant protein, as it is readily available as a by-product of soy oil production.
A high performance material
The new material can perform similarly to high-performance engineering plastics such as low-density polyethylene. Its advantage is that it does not require chemical crosslinking, which is often used to improve the performance and durability of biopolymer films. The most commonly used crosslinking agents are unsustainable and can even be toxic.
“This is the culmination of something we’ve been working on for over 10 years, namely understanding how nature creates materials from proteins,” said Knowles. “We didn’t want to solve a sustainability challenge – we were motivated by curiosity to create strong materials from weak interactions.”
The new product will be marketed by Xampla, a University of Cambridge spin-out company developing replacements for single-use plastic and microplastic. Later this year, the company will introduce a range of single-use bags and capsules that can replace the plastic used in everyday products like dishwasher tabs and detergent capsules.