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Plastic-Eating Bacteria



PET: Both a Blessing and Curse


Ever see those plastic water and pop bottles labelled with number 1? That number refers to polyethylene terephthalate, a common plastic that is often used to make these bottles because of its many benefits such as its impact resistance and light weight. PET plastic continues to be mass-produced more and more due to such advantageous properties, and most of it ends up in non-recycled waste. Together with other widely-used plastics, they account for almost 90% of total plastic production worldwide, according to an article about plastic waste in the marine environment, which is why they are the most commonly found in the environment, specifically in aquatic environments as well. In other words, plastic is non-biodegradable, does not decompose naturally, and therefore ends up in the environment in some way. As more plastic is released into the environment, plastic is increasingly accumulated. The ongoing pandemic has also resulted in a sharp rise in the use of single-use plastics, including masks and takeaway boxes, more than ever before.


Is PET Recyclable?


An article published in CBC News, PET is one of the most recyclable plastics, unlike other plastics that are known to degrade in quality when recycled. In Canada, there was a 79% recovery rate for PET bottles and jars in 2015, as researched by the Continuous Improvement Fund. Thermoforms, which are grocery store clamshell containers like those used for berries and muffins, have a recovery rate of only 11%. There is also another significant concern with PET. The plastic can be recycled over and over again, except when it is used to produce carpets or pillows. Those usually end up in landfills.


PET’s Chemical Structure


Plastic has a chemical structure that makes it extremely difficult to break down because it consists of monomers, tiny molecules that are joined together to form polymers. Many studies have been conducted on the ability of bacteria to break down PET plastic into its constituent monomers. On the other hand, not much research has been done on the ability of these bacteria to identify and absorb the monomers into their cells.


Image is courtesy of research gate.net.


The Discovery of Plastic-Eating Bacteria


There will not be a single solution to this global plastic pollution problem, but the development of microbial degradation of plastics may be a crucial step in addressing it. Ideonella sakaiensis, the first known plastic-eating bacteria, was discovered by Kyoto Institute of Technology’s Kohei Oda, Keio University’s Kenji Miyamoto, and coworkers in March 2016. They discovered a bacteria in sludge outside a bottle recycling facility in Osaka that has gained the ability to break down PET plastic. The bacteria may not be able to digest plastic quickly enough to eliminate the millions of tons of plastic waste that enter the environment each year. However, as a Forbes article explains, this is one of the many breakthroughs that will significantly help lay the foundations for the possible development of industrial-scale facilities, where enzymes gnaw on dumps of plastic or even are sprayed on patches of garbages that amass in the ocean or rivers.


Image is courtesy of Keio Research.


Other Significant Breakthroughs


A year after the Ideonella sakaiensis discovery, scientists have found a fungus that is capable of decomposing plastic at a water disposal facility in Islamabad, Pakistan. In the same year, a biology student at Reed College in Oregon discovered plastic-eating bacteria in samples collected from an oil site in Houston, Texas. After collecting soil from a brittle plastic waste site in Leipzig, Germany, researchers identified bacteria strains that can decompose polyurethane plastic. In 2018, scientists in the U.K. and U.S. altered an enzyme to degrade plastic in just a few days. Later, in October 2020, the process was further improved by joining the bacteria’s two separate plastic-eating enzymes into a single “super enzyme”. A year later, a demonstration plant was opened by Carbios, a French company, last fall for its enzymatic recycling technology.


Is This a Solution to the Plastic Crisis?


Plastic-eating bacteria may be perceived as a scientific advancement for some and a setback for others. It is important to consider if possible solutions may contribute to far bigger problems. Experts suggest that converting to reusable alternatives like Notpla’s seaweed-derived materials will ensure that non-recyclable plastic ends up in a landfill instead of the environment, and that using biodegradable materials where possible are the best approaches to combat the plastic crisis. What we do know so far, however, is that the world cannot recycle its way out of this mess, and there is no one material or one solution that will solve this crisis.



Article Author: Tanya Kor

Article Editors: Sherilyn Wen, Victoria Huang