"Living" plastic decomposes itself after a few days
The plastic from Chinese researchers contains living microbes that form two enzymes that dissolve polymer chains. This happens with high efficiency.
An electrode based on self-decomposing plastic dissolves completely.
(Image: American Chemical Society)
A Chinese research team has developed a plastic that can degrade itself. The polymer-based plastic contains microbes that can completely break down the polymer chains in just six days. This allows for the production of plastics whose decomposition process can be triggered externally at specific times – without leaving behind microplastics.
Many everyday items are made of plastic but are only used for a certain period. However, the plastic items last much longer, must then be disposed of expensively or incinerated. In the worst case, they are carelessly thrown into nature and lead to microplastics with corresponding consequences for people and the environment.
The Chinese research team has thought about how a lifecycle of a plastic can be directly incorporated into the material. The results of their research have been documented by the scientists in the study “Degradable Living Plastics Programmed by Engineered Microbial Consortia,” which was published in ACS Applied Polymer Materials.
The researchers' plastic is based on polycaprolactone, a polymer used in 3D printing and as suture material in surgery. The scientists embedded a dormant spore form of Bacillus subtilis into the material. The microbes are designed to produce two cooperating, polymer-degrading enzymes. One enzyme, the lipase from Candida antarctica, breaks down long polymer chains into short pieces. This happens rather randomly. The other enzyme, however, the lipase from Burkholderia cepacia, breaks down the monomer building blocks from both ends and simultaneously stimulates spore formation. Previous approaches to degrading plastics relied on only a single enzyme.
Activation of decomposition by hot nutrient solution
The plastic produced by the scientists has similar mechanical properties to a polycaprolactone film. To activate the decomposition process, they exposed the plastic to a nutrient solution at 50 °C, which activated the spores, and the resulting enzymes decomposed the plastic completely into its basic building blocks within six days. According to the researchers, this happened with such high efficiency that no microplastics remained.
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As a proof of concept, the researchers created a functioning electrode from their “living” plastic. It decomposed completely within two weeks.
The scientists are now looking for a way to activate the spores when exposed to water for a certain period, for example. “Living” disposable plastics that enter the environment, rivers, and oceans could then decompose themselves, leading to less environmental pollution.
(olb)
