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Plant-Based Material Designed to Replace Plastics

Uses of plant-based material

Uses of plant-based alternative to plastic (Xampla Ltd.)

10 June 2021. Biochemists created a polymer film derived from soy proteins in a sustainable process that can replace many of today’s single-use plastics. A team from University of Cambridge in the U.K. and the spin-off company Xampla Ltd. describe the material and process in today’s issue of the journal Nature Communications.

Researchers from the lab of Cambridge chemistry professor Tuomas Knowles are seeking alternative materials to plastics made into one-off uses like dishwasher and laundry soap tablets, as well as non-degradable films used in packaging and other consumer products. Proteins from plants offer a potential feedstock for these alternatives, but in their natural state plant-based proteins are often insoluble in water, requiring many chemical modifications and purifications. The team set out to find an economical, environmentally-friendly, and scalable method to produce a plastic-like material to replace today’s single-use plastics.

For this process, Knowles and colleagues used the spider as a model. Spiders produce their silk from proteins that self-assemble into a strong, flexible material. “Because all proteins are made of polypeptide chains, under the right conditions we can cause plant proteins to self-assemble just like spider silk,” says Knowles in a university statement. “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.”

Mechanical properties similar to engineered plastics

Researchers in this case started with a soy protein isolate, readily available as a waste product from making soybean oil. The team mixed the protein isolate in water and acetic acid, the main ingredient in vinegar, to form a slurry, then exposed the mix to ultrasound and and 90 degree C heat (194 F). The resulting solution then cools and the protein chains self-assemble into a network forming a densely-packed hydrogel, a water-based polymer gel. The solvent in the hydrogel then evaporates, leaving a clear transparent film. The team later added glycerol, a naturally occurring compound used in pharmaceuticals, as a plasticizer to produce a more uniform and flexible film.

In lab tests, the film exhibited physical and mechanical properties similar to engineered plastics. And the material could also be produced with lithographic templates to add micro- or nanoscale patterns into the film, to make the surface repel water as well as add colors to the film. In another demonstration, the team successfully coated ordinary paperboard with the film, to protect the board surface much like lamination. The authors point out their process uses no toxic solvents, nor other non-biodegradable products.

“The key breakthrough here,” says postdoctoral researcher and co-author Marc Rodriguez Garcia, “is being able to control self-assembly, so we can now create high-performance materials.” He adds, “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.”

Knowles is scientific founder of Xampla, also in Cambridge, a three year-old enterprise commercializing this process. The company is producing alternative feedstocks from plant proteins for microcapsules using engineered plastics, as well as films and coatings. Knowles is an adviser to Xampla, while Rodriguez Garcia is head of research and the paper’s first author Ayaka Kamada is a research scientist at the company. The university filed for patents on the technology.

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