Silk-Inspired Process Produces High-Strength Biodegradable Plant-Based Plastic

Researchers from Wageningen University & Research, the University of Amsterdam, and several institutions in China have developed a high-strength biodegradable plastic using corn protein. They named this transparent material "plantymer." Compared to many existing protein-based plastics, this material has a much lower water absorption rate. The research team has published their findings in Nature Communications.

Drawing inspiration from natural protein structures

Researchers use zein, a protein found in corn, to produce plant-based polymers. For decades, manufacturers have been exploring the use of this protein as a raw material for fibers and bioplastics. The research team first dissolved the zein in an ethanol–water mixed solution. When the solution reached the transition point, it formed a viscous protein-rich substance.

Researchers extruded the material through tiny holes to produce textile fibers; it can also be spread out on a flat surface and dried to form a thin film. The film is about as thick as a heavy-duty trash bag.

The inspiration for this preparation process comes from the mechanism of spider silk spinning. During extrusion or rolling, mechanical forces alter the structure of the protein chains. The spring-like α-helix structures transform into flatter β-sheet structures. These folded structures interlock with each other, forming physical crosslinks without the need for additional chemical reagents.

This structural transformation gives the material a tensile strength higher than that of commonly used polyethylene, but its strength still falls short of metals. Similar protein structures are also found in spider silk, mussel adhesive substances, and the teeth of squid suckers. It came as a surprise to the researchers that this structural effect could be achieved in plant proteins.

Water resistance has been improved.

Water sensitivity remains a major challenge for bioplastics. After being immersed in water for one hour, plant-polymer films absorb about 25% of their own weight in water. By comparison, soy-based plastics can have a water absorption rate of around 175%. Traditional polyethylene terephthalate (PET) still exhibits excellent performance, with a water absorption rate of only about 0.1%.

According to reports, most plant-based polymers can biodegrade completely within four weeks without producing microplastics. Combining high strength with biodegradability, they are suitable for agricultural films and other short-term-use products. Researchers believe the material could also be used for disposable cutlery, plates, straws, packaging films, and textile fibers.

Raw Materials and Large-Scale Production Challenges

This technology is still in the early stages of research. So far, Chinese research teams have only produced films of about one square meter. The process has the potential for large-scale production, but corn protein as a raw material has a drawback: the production materials may compete with humans and livestock for food resources.

To this end, researchers are seeking alternative protein sources, with poultry feathers and processing by-products from beer production among the options under consideration. More applied research on this material is still needed. To achieve commercial application, researchers must also evaluate its production process, safety, performance in use, and environmental impact after disposal.