Thermoplastic polyurethanes (TPUs) are extremely flexible and durable elastomers that can be used in a variety of applications such as automobile parts, footwear, medical devices, electronic devices, etc. However, there is no commercially-available recycling stream for TPUs, and thus most TPUs end up as waste in landfills. At the same time, slow degradation rates of TPUs in nature also make plastic pollution more serious. To mitigate the plastic pollution arising from TPU waste, herein, we propose incorporating bacterial spores as living filler materials during the melt processing of TPUs to improve both biodegradation and mechanical properties. We first screened and selected TPU-degrading and spore-forming bacteria. The bacterial strain was metabolically engineered to acquire improved heat tolerance because melt processing of TPUs often requires high temperatures up to 200 °C. Tensile tests revealed that incorporating spores as micron-scale fillers positively affected the mechanical properties of TPUs. We also extracted spores from the biocomposite TPUs and tested their viability. Colony forming unit assays showed significant survival of spores after the melt processing. It is also important to note that spores extracted from the biocomposite TPUs could be germinated into vegetative cells under the proper nutrition, representing the potential of spores in biocomposite TPUs for triggering biodegradation. This work demonstrates that spore-incorporated biocomposite TPUs can be a more sustainable option compared to standard TPUs, one of the most widely used polymers in the world, with improved tensile properties.

Spore-incorporated biocomposite TPUs with improved toughness and biodegradation

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ACS Fall 2022

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