Scientists have devises different means to develop living plastics that can be programmed to break themselves down when triggered. Many plastic items are made for one-time use, but the materials can remain in the environment for years.
But the researchers has up with living plastics built with microbes that can be activated to break down the polymer when needed. In a study published in ACS Applied Polymer Materials, a research team used two cooperating bacterial strains to fully degrade the plastic in only six days without producing microplastics.
A corresponding author of the study, Zhuojun Dai explains that “the realisation that traditional plastics persist for centuries, while many applications, like packaging, are short-lived, led us to ask: Could we build degradation directly into the material’s life cycle?” Some microbes make enzymes that can cut long polymer chains into smaller fragments.
Since plastics are polymers, researchers can potentially place those enzymes, or the microbes that produce them, directly into living plastic materials. “By embedding these microbes, plastics could effectively ‘come alive’ and self-destruct on command, turning durability from a problem into a programmable feature,” Dai explained.
Moving from earlier efforts that were mostly based on one enzyme, the scientists, including Dai, Jin Geng, Dianpeng Qi and others aimed to make the breakdown process more efficient. They engineered Bacillus subtilis to produce two polymer degrading enzymes that work in sequence.
One enzyme cuts long polymer chains into smaller pieces at random points, while the second breaks those smaller pieces down from the ends into their monomer building blocks.
The researchers combined dormant B. subtilis spores with polycaprolactone (a polymer common in 3D printing and some surgical sutures), allowing the microbes to remain protected until activation.
The living plastic that resulted had mechanical properties close to ordinary polycaprolactone films. When the researchers added a nutrient broth heated to 122 degrees Fahrenheit (50 degrees Celsius), the spores became active and degraded the plastic completely into its basic building blocks within six days.
Because the two enzymes worked together so effectively, the process avoided generating microplastic particles during breakdown. Early devices also broke down As an early demonstration, the team made a wearable plastic electrode from the living plastic.
The device worked as expected and then fully degraded within two weeks. Next, the researchers want to create a way to activate the spores in water, where much plastic pollution eventually accumulates.
Although the work centered on one polymer, the same general strategy could potentially be adapted for other plastics, including materials often used in single-use products.
The study was partly funded by the National Key Research and Development Program of China, the Shenzhen Medical Research Fund, the National Natural Science Foundation of China, the Guangdong Natural Science Funds for Distinguished Young Scholars, and the Shenzhen Science and Technology Programme.
