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A groundbreaking advancement in bioplastics could significantly reduce the environmental footprint of the plastic industry. Led by researchers at the University of California San Diego, a team has successfully developed a biodegradable form of thermoplastic polyurethane (TPU), a commonly used commercial plastic known for its softness and durability in products such as footwear, floor mats, cushions, and memory foam.
Detailed in a paper published on April 30 in Nature Communications, the innovative biodegradable TPU is filled with bacterial spores derived from a strain of Bacillus subtilis. These spores possess the remarkable ability to break down plastic polymer materials, offering a sustainable solution to plastic waste.
“It’s an inherent property of these bacteria,” explained Jon Pokorski, nanoengineering professor at UC San Diego and co-lead of the university’s Materials Research Science and Engineering Center (MRSEC). “We selected strains based on their ability to utilize TPUs as a sole carbon source, ultimately identifying the most effective strain for our purposes.”
Unlike fungal spores, bacterial spores are resistant to harsh environmental conditions, owing to a protective protein shield. This resilience enables them to survive in a dormant state until triggered by specific conditions, such as exposure to nutrients present in compost.
To create the biodegradable plastic, researchers fed Bacillus subtilis spores and TPU pellets into a plastic extruder, where they were mixed and melted at 135 degrees Celsius. The resulting material was then extruded as thin plastic strips. Remarkably, the material demonstrated significant biodegradability even in microbe-free environments, breaking down up to 90% within five months when exposed to compost conditions.
“What’s remarkable is that our material breaks down even without the presence of additional microbes,” Pokorski noted. “This versatility makes our technology particularly promising, as it can potentially degrade in a variety of environments.”
Furthermore, the bacterial spores act as strengthening fillers for the TPU, enhancing its mechanical properties such as stretchability and tensile strength.
“Our process of bacterial evolution and selection resulted in a strain optimized to tolerate the high temperatures necessary for TPU production,” stated Adam Feist, bioengineering research scientist at UC San Diego. “The addition of spores not only facilitates biodegradation but also enhances the material’s mechanical properties.”
While the study focused on producing lab-scale quantities, the researchers are actively working on scaling up production for industrial use. Future efforts include evolving bacteria to accelerate plastic degradation and exploring other types of plastics beyond TPU.
“This breakthrough represents a significant step towards addressing the environmental challenges posed by plastic waste,” Feist emphasized. “Our goal is to expand the scope of biodegradable materials to contribute to a more sustainable future.”
The research was supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy, UC San Diego Materials Research Science and Engineering Center (MRSEC), and the National Science Foundation.
