Researchers have created a plant-based, sustainable, scalable material that could replace single-use plastics
The researchers, from the University of Cambridge, created a polymer film by mimicking the properties of spider silk, one of the strongest materials in nature. The new material is as strong as many common plastics in use today and could replace plastic in many common household products. The material was created using a new approach for assembling plant proteins into materials that mimic silk on a molecular level. The energy-efficient method, which uses sustainable ingredients, results in a plastic-like free-standing film, which can be made at industrial scale. Non-fading ‘structural’ colour can be added to the polymer, and it can also be used to make water-resistant coatings. The material is home compostable, whereas other types of bioplastics require industrial composting facilities to degrade. In addition, the Cambridge-developed material requires no chemical modifications to its natural building blocks, so that it can safely degrade in most natural environments. The results are reported in the journal Nature Communications. For many years, Professor Tuomas Knowles in Cambridge’s Yusuf Hamied Department of Chemistry has been researching the behaviour of proteins. Co-author Dr Marc Rodriguez Garcia, a postdoctoral researcher in Knowles’ group began looking at how to replicate this regular self-assembly in other proteins.
The researchers successfully replicated the structures found on spider silk by using soy protein isolate, a protein with a completely different composition. “Because all proteins are made of polypeptide chains, under the right conditions we can cause plant proteins to self-assemble just like spider silk,” said Knowles, who is also a Fellow of St John's College. “In a spider, the silk protein is dissolved in an aqueous solution, which then assembles into an immensely strong fibre through a spinning process which requires very little energy.” The researchers used soy protein isolate (SPI) as their test plant protein, since it is readily available as a by-product of soybean oil production. Plant proteins such as SPI are poorly soluble in water, making it hard to control their self-assembly into ordered structures. The new technique uses an environmentally friendly mixture of acetic acid and water, combined with ultrasonication and high temperatures, to improve the solubility of the SPI. This method produces protein structures with enhanced inter-molecular interactions guided by the hydrogen bond formation. In a second step, the solvent is removed, which results in a water-insoluble film. The material has a performance equivalent to high-performance engineering plastics such as low-density polyethylene.
Source: University of Cambridge news release