Plastic products could soon have a built-in self-destruct feature. Scientists have found a way to incorporate bacteria into plastic products that can completely break down the plastic after activation. If this technique is applied widely, it could greatly reduce the amount of plastic pollution in the environment.
A plastic kill switch
Scientists have created a plastic capable of degrading quickly without producing microplastics, according to a study published in the journal ACS Applied Polymer Materials. The key is using microbes. Living plastics “contain dormant microbes capable of degrading the surrounding polymer,” said a release about the study. Earlier living plastic designs “often depended on a single enzyme, which limited how efficiently the material could be broken down.” However, in the new study, researchers engineered the bacteria “Bacillus subtilis to produce two polymer-degrading enzymes that work together.”
The two enzymes team up to break down the plastic polymers. The first enzyme “cuts the long polymer chains at random points, reducing them into shorter sections,” while the second enzyme “works from the ends of those fragments, breaking them down further into their individual monomer building blocks,” said the release. With the embedded microbes and the enzymes, “plastics could effectively ‘come alive’ and self-destruct on command, turning durability from a problem into a programmable feature,” Zhuojun Dai, a corresponding author on the paper, said in the release.
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The researchers “incorporated dormant spores from the engineered bacteria into polycaprolactone (PCL), a biodegradable polyester used in products ranging from surgical sutures to 3D printing materials,” said Food & Wine. The living plastic material “retained the strength and structure of conventional plastic but could be triggered to degrade when no longer needed.” The scientists “activated the dormant spores by placing the material in a warm nutrient broth heated to about 122 Fahrenheit,” where the “spores began producing both enzymes, which together had completely broken down the plastic within six days.”
Worldly applications
Most of the world’s plastic ends up in landfills or the ocean. Plastic can take anywhere from 20 to hundreds of years to break down because of its chemical structure. It can also degrade into microplastics, which have “turned up in water, food and even human bodies,” raising a number of health concerns, said The Cool Down. But creating plastic that can break down completely rather than releasing tiny fragments “could reduce one path for that contamination.” Still, the living plastic has not yet been “validated in real-world conditions in the ocean, a landfill or a roadside ditch,” said ZME Science.
Plastic that decomposes in a short time period makes “life easier for consumers by reducing the buildup of everyday products that turn into long-lasting trash,” said The Cool Down. In addition, if “disposable packaging, medical products or short-term electronics can degrade more cleanly, communities could face lower cleanup costs and less expensive waste management over time.”
While the researchers only incorporated the bacterial spores in one type of plastic, they eventually hope to “develop a method that activates the bacterial spores in water, where a significant share of plastic pollution accumulates,” said the release. The same strategy used for the PCL “could be adapted for other materials, including plastics widely used in disposable products.”
