Every year, nearly 300 million tons of plastic products such as bags, bottles, and straws are produced around the world. Many of these items end up as waste, which can take up to 450 years to degrade. With this in mind, Cambridge University scientists have developed an environmentally friendly alternative that can withstand daily use.
Spider silk is a naturally strong, lightweight, and flexible material produced by spiders. The goal of the research team was to create a synthetic material that was similar to spider silk and could be used as a polymer-like substance by manufacturers. The team created a self-standing scaffold (or membrane) using plant proteins, which they refer to as “vegan spider silk.”
The structure is similar to silk on a molecular level, and researchers claim it is simple to mass-produce. Manufacturers won’t need to use dyes or chemicals that can leak and contaminate the environment or other goods because the material can be textured to add color. Researchers can also shape it into items that are similar to today’s plastics.
Tuomas Knowles, a professor of physical chemistry and biophysics, has spent years researching protein function and activity, particularly the impact of misshaped protein structures on their function. He and his colleagues have looked into the role of abnormal proteins in diseases like Alzheimer’s.
“We normally investigate how functional protein interactions allow us to stay healthy and how irregular interactions are implicated in Alzheimer’s disease, disclosed by the lead researcher in a university release. “It was a surprise to find our research could also address a big problem in sustainability: that of plastic pollution.”
He and his team also looked at the molecular structure of spider silk while studying these protein structures. The goal was to figure out what mechanism gives silk its strength, knowing that it has weak molecular interactions.
“We discovered that one of the key features that gives spider silk its strength is the regular arrangement of hydrogen bonds in space and at a very high density,” says Knowles.
The researchers then proposed a method for other proteins, such as plant proteins, to assemble themselves in the same way.
“We know very little about the self-assembly of plant proteins,” says PhD candidate Ayaka Kamada, the paper’s first author. “It’s exciting to know that by filling this knowledge gap, we can find alternatives to single-use plastics.”
Using food waste to create useful items
They discovered that a soybean protein was capable of forming these repeating structural patterns with strong hydrogen bonds. The soybean proteins created a scaffold that was remarkably similar to silk. Given that soybeans are a major food waste product, the team hails this as a game-changing discovery.
“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 explains. “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.”
“Other researchers have been working directly with silk materials as a plastic replacement, but they’re still an animal product,” says Dr. Marc Rodriguez Garcia. “In a way, we’ve come up with ‘vegan spider silk’ – we’ve created the same material without the spider.”
The substance’s strength comes from the repeating pattern of the soy isolate proteins, which creates a resilient, sustainable, and non-toxic material comparable to top-of-the-line engineering polymers.
“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 adds. “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.”
“The key breakthrough here is being able to control self-assembly, so we can now create high-performance materials,” Rodriguez Garcia states. “It’s exciting to be part of this journey. 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.”