'Living Plastic' Seemed Impossible, Until It Actually Worked

Plastic products are everywhere, and with good reason. Plastic is relatively cheap to produce at around $0.70 to $1.20 per pound, and convenient for when you need a single use or relatively temporary item, like utensils or bottles. But the trade-off that comes along with those temporary and cheap products is the damage they do to our ecosystems. Every year 20 million metric tons of plastic end up in our environment and the number is expected to continue rising. Since it can take up to 1,000 years for plastic to corrode, let alone fully biodegrade, we need to find a compromise. Like, say, a sort of "living plastic" that's durable enough for production but puts less of a strain on our natural resources because it breaks down quickly. Cue science to the rescue!

Scientists are testing a way to make plastic with embed microbes that can survive production processing and then break down the polymers that the plastic is made from. As the polymer chains become smaller, enzymes in the microbes begin to break them down even further until the degradation process is complete. But, don't worry that your dinner plate is about to crumble in front of your eyes and spill that meal into your lap, because science figured that part out, too.

The trick to creating a durable, yet biodegradable plastic requires a way to intentionally activate the enzymes only when ready. Otherwise, the plastic could degrade too quickly and become porous and unstable. To solve this, researchers focused on two areas: focusing on one microbe that can be engineered for a specific enzyme production and controlling the method by which it activates.

Currently, that star microbe is Bacillus subtilis, a fast-growing organism that is excellent at secreting proteins and naturally creating biofilms. Scientists in the study tinkered with B. subtilis and engineered a version that produces polymer-degrading enzymes with a dual-pronged approach. One enzyme starts by cutting down long polymer chains that hold plastic together. By severing the chains into smaller chunks it allows the second enzyme to attack the short chains from the ends working its way to the middle, like some sort of bacterial "Lady and the Tramp" pasta scene.

But B. subtilis needs to stay dormant and let those long polymers do their thing until the plastic is ready for disposal. To do this, scientists embedded the bacterium in its spore form and combined it with the polymer polycaprolactone, essentially entombing it until ready. Then, they created a heated nutrient solution designed specifically to make the spores "come online" and break down the rest of the polymers. Within six days of activation, the plastic was nothing but its basic building blocks, making it easier to recycle and reuse.