Living Plastics: A Revolutionary Approach to Sustainable Plastic Degradation

Plastics have become an integral part of modern life, but their durability and resistance to degradation have led to significant environmental concerns. To address this pressing issue, Dr. DAI Zhuojun’s research group at the Shenzhen Institute of Advanced Technology (SIAT), part of the Chinese Academy of Sciences (CAS), has developed a groundbreaking solution—degradable "living plastics" engineered through synthetic biology and polymer engineering. Their study, titled "Degradable Living Plastics Programmed by Engineered Spores," was recently published in *Nature Chemical Biology* and presents a novel method for creating environmentally friendly plastics that can break down under specific conditions.

Harnessing the Power of Natural Resilience

The innovative approach taken by the SIAT team leverages the natural resilience of Bacillus subtilis spores, which are known for their ability to withstand extreme environmental conditions such as dryness, high temperatures, and high pressure—conditions that are also typical in plastic processing. The researchers genetically engineered these spores to produce Burkholderia cepacia lipase (BC-lipase), a powerful enzyme that can degrade plastic materials.

These engineered spores were then mixed with poly(caprolactone) (PCL), a biodegradable polyester, to create "living plastics." The spores remain dormant within the plastic matrix under normal conditions, ensuring that the material retains its physical properties and stability during regular use. However, when the plastic surface is eroded or exposed to specific environmental triggers, such as composting, the spores become activated. Upon activation, they begin to secrete the plastic-degrading enzyme, initiating a process that leads to the near-complete breakdown of the plastic.

Innovative Degradation Mechanisms

The research demonstrated two primary methods for releasing the spores and initiating the degradation process. In the first method, an external enzyme, lipase CA, is used to erode the plastic surface, allowing the spores to germinate and express BC-lipase. This results in a rapid and efficient degradation of the PCL plastic, with molecular weights dropping to less than 500 g/mol within six to seven days. In contrast, ordinary PCL plastics subjected only to surface damage without spore activation retained a significant amount of debris even after 21 days.

The second method involves composting the living plastics in soil. Without any external agents, the plastics degraded completely within 25 to 30 days, while traditional PCL plastics took about 55 days to degrade to a similar level, which was invisible to the naked eye.

Beyond PCL: Broadening the Scope

Recognizing the potential of this technology, the research team tested the applicability of their method with other types of commercial plastics, including polybutylene succinate (PBS), polybutylene adipate-co-terephthalate (PBAT), polylactic acid (PLA), polyhydroxyalkanoates (PHA), and even polyethylene terephthalate (PET). The results were promising: the spores could survive processing temperatures as high as 300°C and, once released through physical grinding or environmental triggers, could still revive and express their plastic-degrading capabilities.

Industrial Potential and Future Implications

To assess the scalability of this technology, the research team conducted a small-scale industrial test using a single-screw extruder on the PCL system. The resulting living plastics maintained their shape and stability during service, even in challenging conditions like immersion in Sprite for two months. Once triggered, the living plastics degraded rapidly, further demonstrating their practical viability for industrial applications.

This research represents a significant advancement in the field of sustainable materials. By embedding engineered spores into plastic matrices, the SIAT team has created a new class of plastics that combine the durability needed for practical use with the ability to degrade efficiently when their useful life is over. This breakthrough offers a promising solution to the global plastic pollution crisis, with the potential to revolutionize the way plastics are manufactured, used, and disposed of in the future.

Conclusion

The development of "living plastics" by Dr. DAI Zhuojun’s team at SIAT marks a major milestone in the quest for sustainable materials. By leveraging synthetic biology and polymer engineering, the team has introduced a novel method for creating plastics that are both durable in everyday use and capable of rapid degradation under specific environmental conditions. This innovation not only addresses the urgent issue of plastic pollution but also opens new avenues for the development of eco-friendly materials that can contribute to a more sustainable future.