Researchers at the University of California San Diego have developed a biodegradable form of thermoplastic polyurethane (TPU) filled with bacterial spores that break down the material in compost environments. The study, published in Nature Communications, utilized bacterial spores from Bacillus subtilis, which have the ability to break down plastic polymer materials. These spores were specifically selected for their ability to use TPUs as a carbon source, making them ideal for breaking down the plastic material effectively.
Bacterial spores were chosen for their resistance to harsh environmental conditions and protective protein shield that allows bacteria to survive in a dormant state. The researchers fed Bacillus subtilis spores and TPU pellets into a plastic extruder, melted and mixed them, and extruded the resulting material into thin plastic strips. The biodegradable plastic strips were then put into compost setups at a controlled temperature and humidity, triggering the germination of the spores and leading to 90% degradation within five months.
One key advantage of this biodegradable material is its ability to break down even without additional microbes present, making it versatile for various environments. The researchers also engineered the bacterial spores to withstand the high temperatures required for TPU production using a process called adaptive laboratory evolution. This process involved subjecting the spores to extreme temperatures, allowing them to naturally mutate and selecting the most resilient strains for further testing.
In addition to breaking down plastics, the bacterial spores also served as a strengthening filler in the TPU material, enhancing its mechanical properties such as tensile strength and stretchability. The researchers plan to optimize the production process for industrial scale use, explore other types of plastics beyond TPU, and evolve the bacteria to break down plastics more efficiently. This study was supported by various funding sources, including the U.S. Department of Energy, UC San Diego Materials Research Science and Engineering Center, and the National Science Foundation.
Overall, the development of this biodegradable TPU material represents a significant step towards reducing the environmental impact of the plastic industry. By using bacterial spores that can break down plastic materials in compost environments, the researchers have created a versatile and sustainable alternative to traditional plastics. Further research is needed to optimize the production process and explore other types of plastics that can benefit from this technology.
