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If there’s any one thing that most people tend to associate with environmental degradation, it’s plastic. For the last few decades, plastic has been one of the most important commercial building blocks available, providing cheap, durable items that are easy to mass-produce. Only recently have we learned of the immense environmental consequences that come with using and disposing plastics. Plastic doesn’t decay like natural substances do; it takes some forms of plastic a thousand years or more to break down, and even then it lingers in the form of minuscule microplastics that can build up inside the tissues of living things. These two things combined makes it easy for plastic to build up in the world’s natural spaces, and it makes recycling plastic a difficult, often fruitless endeavor. As our plastic output continues to increase, it should come as no surprise that scientists and environmental activists are scrambling for a solution to the world’s growing plastic problem. This heightened interest has turned up a few interesting options, one of them being organisms that can break down plastic. In recent years, scientists have discovered bacteria, enzymes, and fungi that can all break down plastic—but are they the solution we need to put our plastic problems well and truly behind us?
Well, yes and no.
As of right now, we have discovered over ninety genera of natural organisms that can break down plastic material. Not all of these are equally effective; as a matter of fact, only a handful have risen up as prime candidates for addressing the vast amounts of plastic that currently clutter our wild spaces. That said, the few options that researchers have focused on show immense promise for tackling portions of the current plastic crisis.
The first, and most popular, of these plastic-eaters is an enzyme known as PETase that was first isolated from bacteria in 2016. PETase is an enzyme that specializes in destroying one particular type of plastic known as PET—polyethylene terephthalate. PET is the primary component of many disposable plastics such as water bottles, as well as other commonly-produced items like plastic-derived cloth. PET plastics represent about one fifth of all the plastic in the world, and many items made with PET are known to be big polluters of natural ecosystems. The discovery of an enzyme that can break PET down, then, is big news—but how effective is it?
In the beginning, PETase wasn’t very effective, taking a long time to break down plastics and producing byproducts that were only dubiously useful. As scientists have continued to research the enzyme and modify the genes that produce it in bacteria, new strains of the PETase enzyme have been developed that enhance the enzyme’s speed. Uses have also been found for the byproducts it creates, including a modified form of PET plastic that can be recycled again and again using PETase. Currently, recycling efforts are very choosy about what plastics they can accept, and the recycled material usually winds up too degraded to be returned to a recyclable form. Such recycled plastic is instead used to make more single-use items like cheap plastic-based carpets that eventually wind up in landfills or the environment. The emergence of a process that can infinitely recycle certain types of plastic is big news, both for the average consumer who might not be inclined to turn entirely away from plastic and the companies who otherwise shy from recycling on account of its expense and low economic return. Researchers have also recently discovered a way to convert a once-useless byproduct of the PETase reaction into a much more useful form. Using a string of enzymes and reactions, that byproduct can eventually be converted into a natural material known as protocatechuic acid, or PCA. PCA is found in many plants and has notable medicinal effects.
Other than PETase, a big scientific spotlight has also been given to plastic-eating fungi. Fungi like Pestalotiopsis microspora can break down polyurethane and use its components as fuel—consuming no oxygen all the while. Though research into the large-scale use of fungi still appears to be ongoing, fungal plastic breakdown may represent an ideal option for the average person. Unlike PETase and other plastic-deconstructing enzymes and bacteria, which currently require special treatment in scientific facilities, fungi like Pestalotiopsis microspora could much more easily be brought into homes and used in devices akin to a composting bin. Some early studies even report that certain forms of P. microspora are safe to consume, meaning that such devices could potentially be used to produce food while munching away on a household’s plastic.
While both PETase and P. microspora sound like great options to address the world’s plastic problems, there is one very big issue that still lies in the path of these technologies: scale. Right now, neither PETase nor fungi like P. microspora can be implemented on a large enough scale to make a dent in the rate of plastic that is disposed each year. Furthermore, both of these technologies take a while to work, meaning that they are currently less appealing to the companies who might consider them as an alternative to traditional methods of recycling. The cost of using them also discourages their implementation on a large scale, and not all types of plastic can currently be broken down through organic means. Even still, there is a silver lining: some companies are beginning to harness these technologies in the hope of appealing to the environmentally conscious. It is possible that bottles made using PETase recycling will begin hitting the shelves as early as 2024, though they’ll be more pricey than your average bottle. If the launch of such “infinitely recyclable” bottles is a success, the publicity it garners will be a massive boon for this technology—exciting interest within both the public and the industry. Until then, plastic-consuming organisms will likely remain rather anonymous in the big picture as they continue to develop and improve. They may not represent the full solution to disposable plastic, but they certainly offer a valuable starting point for a sustainable future.
References & Further Reading
This article by Forbes provides a comprehensive look into the present and future of plastic-degrading technology. It covers the current state of the technology as well as some of the drawbacks associated with its future as a large-scale technology—like the potential danger of releasing bioengineered organisms into the environment at large.
This article by Science.org examines plastic-eating bacteria and enzymes in detail, describing the way they work, the research currently being invested in them, and their future as a form of recycling. It is a detailed and interesting read for anyone who found their interest piqued by this article's brief overview.
This article dives into the interesting world of Pestalotiopsis microspora, describing the way it functions and detailing its potential as a home recycling option.
This brief article by the Smithsonian details the research and technology behind one prototype design for using P. microspora as both a plastic recycler and a food producer. It is a great choice for those of you who want a short primer on the subject, and it includes a video of the prototype "fungi mutarium" where this interesting process may eventually take place in our homes.
This article offers a comprehensive answer as to why plastic-destroying technologies haven't become mainstream options for recycling. I highly recommend it as a supplement to the STEMx article written above; while some of the technology's current drawbacks were covered in our article, the full picture is best gleaned from this informative source.
This YouTube video from earlier in 2022 describes new findings about using the byproducts of plastic-eating enzymes like PETase. It is short, thorough, and represents some of the newest news in regard to this fascinating technology.
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