Although many plastic products are only used for minutes or hours, the materials can remain in the environment for decades or even centuries. Researchers are now investigating a different approach: plastics designed to break down on their own when activated.
These materials, known as living plastics, contain dormant microorganisms that can degrade the surrounding polymers. In a study published in ACS applicable polymer materialsScientists have developed a version that completely decomposes in six days without producing microplastics.
“The realization that traditional plastics last for centuries, while many applications such as packaging are short-lived, led us to wonder if it was possible to incorporate degradation directly into the material’s life cycle,” explains Zhuojun Dai, corresponding author of the paper.
Turning microorganisms into built-in processing systems
Some microorganisms naturally produce enzymes that cut long polymer chains into smaller pieces. Because plastics are made from polymers, researchers have been studying whether these enzymes, or the microorganisms that produce them, can be embedded directly into plastic materials.
“By embedding these microbes, plastics can effectively ‘come to life’ and self-destruct on command, turning durability from a problem to a programmable function,” Dai explains.
Previous living plastic designs often relied on a single enzyme, limiting the efficiency of material degradation. To improve the process, Dai, Jin Geng, Dianpeng Qi et al. Bacillus subtilis It produces two polymer-degrading enzymes that work together.
The first enzyme cuts long polymer chains at random positions, reducing them to shorter parts. The second step then works from the ends of these fragments and further breaks them down into individual monomeric building blocks.
Complete disassembly in 6 days
Researchers found that the dormant Bacillus subtilis Spores containing polycaprolactone, a polymer common in 3D printing and some surgical sutures. By keeping the bacteria in spore form, the team was able to protect them until they were ready to begin the decomposition process.
The finished living plastic had mechanical properties similar to regular polycaprolactone film. It maintained its strength and functionality under normal conditions, suggesting that the addition of spores did not significantly weaken the material.
To activate the bacteria, the team added nutrient broth heated to 122 degrees Fahrenheit (50 degrees Celsius). The spore became active and began producing two enzymes. Within six days, the plastic was completely broken down to its basic components.
Because the enzymes work in sequence, the material doesn’t just break down into tiny plastic pieces. This process was efficient enough to prevent the generation of microplastics during decomposition.
Disappearing wearable devices
To demonstrate the potential for real-world use, researchers created wearable plastic electrodes from biomaterials. The device worked as intended, but completely degraded within two weeks of startup.
The results suggest that living plastics could eventually be used in products that need to remain durable for a limited period of time, but should not persist after being disposed of.
Expansion of technology to other plastics
The research team now hopes to develop a way to activate bacterial spores in water, where a significant portion of plastic pollution accumulates.
Although the experiments focused on a single polymer, the researchers believe the same general strategy can be applied to other materials, including plastics, which are widely used in disposable products.
The authors acknowledge funding from the China National Key Research and Development Program, Shenzhen Medical Research Fund, National Natural Science Foundation of China, Natural Science Foundation for Outstanding Young Scholars of Guangdong Province, and Shenzhen Science and Technology Program.
