Researchers have created a plant-based, durable, scalable material that can replace disposable plastics in many consumer products.
Researchers at the University of Cambridge have created a polymer film that mimics the properties of spider silk, one of the strongest materials in nature. The new material is as strong as many ordinary plastics used today, and can replace plastic in many ordinary household products.
The material was created using a new approach to collect plant proteins into materials that mimic silk at the molecular level. The energy-efficient method, which uses sustainable ingredients, results in a plastic-like free-standing film that can be made on an industrial scale. A non-fading “structural”
The material can be composted at home, while other types of bioplastics require industrial composting facilities to decompose. In addition, the material developed at Cambridge does not require chemical modifications to its natural building blocks so that it can be safely degraded in most natural environments.
The new product will be commercialized by Xampla, a company from the University of Cambridge that develops disposable substitutes for plastics and microplastics. Later this year, the company will introduce a set of sachets and disposable capsules that can replace the plastic used in everyday products such as dishwasher tablets and detergent capsules. The results are reported in the journal Nature Communications.
For many years, Professor Toomas Knowles of the Department of Chemistry at Yusuf Hamid in Cambridge studied the behavior of proteins. Much of his research has focused on what happens when proteins break down or “misbehave” and how it relates to health and human diseases, most notably Alzheimer’s.
“We usually look at how functional protein interactions allow us to stay healthy and how irregular interactions are linked to Alzheimer’s disease,” said Knowles, who is leading the current study. “It was a surprise to find that our research could also address a major sustainability problem: that of plastic contamination.”
As part of their research on proteins, Knowles and his group are interested in why materials like silk spider are so strong when they have such weak molecular bonds. “We found that one of the key characteristics that gives spider silk strength is that hydrogen bonds are arranged regularly in space and at very high densities,” Knowles said.
Co-author Dr. Mark Rodriguez Garcia, a postdoctoral fellow in the Knowles Group who is now head of research and development at Xampla, began looking at how to replicate this regular self-assembly into other proteins. Proteins have a tendency to molecular self-organization and self-assembly, and in particular plant proteins are abundant and can be sustainably supplied as by-products of the food industry.
“Very little is known about self-assembly of plant proteins, and it is exciting to know that by filling this knowledge gap, we can find alternatives to disposable plastics,” he said. the candidate Ayaka Kamada, the first author of the newspaper.
The researchers successfully reproduced the structures found on the silk spider using a soy protein isolate, a protein with a completely different composition. “Because all proteins are made up of polypeptide chains, under the right conditions we can make plant proteins self-assemble just like a silk spider,” Knowles said. “In a spider, the silk protein is dissolved in an aqueous solution, which is then assembled into an extremely strong fiber by spinning, which requires very little energy.”
“Other researchers have worked directly with silk materials as a plastic substitute, but they are still an animal product,” said Rodriguez Garcia. “Somehow we came up with ‘vegan spider silk’ – we created the same material without the spider.”
Each plastic substitute requires a different polymer – the two in nature that exist in abundance are polysaccharides and polypeptides. Cellulose and nanocellulose are polysaccharides and have been used in a number of applications, but often require some form of crosslinking to form strong materials. Proteins are assembled and can form strong materials such as silk without any chemical modifications, but they are much more difficult to work with.
The researchers used soy protein isolate (SPI) as their test vegetable protein because it is readily available as a by-product of soybean oil production. Plant proteins such as SPI are poorly soluble in water, which makes it difficult to control their self-assembly into ordered structures.
The new technique uses an environmentally friendly mixture of acetic acid and water combined with ultrasound and high temperatures to improve the solubility of SPI. This method produces protein structures with enhanced intermolecular interactions, guided by the formation of a hydrogen bond. In a second step, the solvent is removed, resulting in a water-insoluble film.
The material has characteristics equivalent to highly efficient engineering plastics such as low density polyethylene. Its strength is in the correct arrangement of the polypeptide chains, which means that there is no need for chemical crosslinking, which is often used to improve the efficiency and stability of biopolymer films. The most commonly used crosslinking agents are unstable and may even be toxic, while the Cambridge technique does not require toxic elements.
“This is the culmination of something we’ve been working on for more than ten years, which is understanding how nature generates protein materials,” Knowles said. “We didn’t tackle the sustainability challenge – we were motivated by curiosity about how to create strong materials from weak interactions.”
“The key breakthrough here is the ability to control self-assembly, so we can now create highly efficient materials,” said Rodriguez Garcia. “It’s exciting to be a part of this journey. There’s a huge, huge problem with plastic pollution in the world, and we’re in a happy position to be able to do something about it.”
How does a spider spin its self-assembled silk?
Nature Communications (2021). DOI: 10.1038 / s41467-021-23813-6
Provided by the University of Cambridge
Quote: Vegan spider silk provides a sustainable alternative to disposable plastics (2021, June 10), retrieved on June 11, 2021 from https://phys.org/news/2021-06-vegan-spider-silk -sustainable-alternative.html
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