Garbage-Eating Bacteria: Evolution's Answer to our Plastic Plague

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Imagine an island twice the size of Texas, floating in the dead middle of the Pacific ocean, made of nothing but the contents of your trash can. Would you want to swim in those waters? How about eating the fish that swim within them? As disgusting and as detached from reality as that sounds, the Great Pacific Garbage Patch, though not yet an actual island, seems a strange premonition to the gross, surrealist future we can now only imagine. 

Located between the coasts of California and Hawaii, the Great Pacific Garbage Patch is formed by plastic waste that flows into the oceans from the world’s rivers, and which, given its low density, does not sink to the bottom of the ocean. Rather, plastic floats, covering an area that is now reported to have exceeded 1.6 million square kilometers: three times the size of France. That’s the equivalent of 80,000 tonnes of plastic, which means just about 1.8 trillion plastic pieces float in the world’s biggest garbage patch. For reference, that would mean just about 250 pieces of plastic debris per human on the planet float along in just one of six of the massive garbage patches that exist in our planet’s body of water, as the video below, produced by the Ocean Cleanup visually explains.

It’s no secret. Our consumption of non-biodegradable plastic is enormous and unsustainable, we are warned of it constantly. The six garbage patches that inhabit our oceans continue their relentless growth while we scramble for viable solutions. The issue here, however, is not so much our consumption of plastic, but rather our efforts towards its sensible removal, as we’ve yet to find any sustainable path towards degrading our immense plastic output. We have no way of cleaning up the disgusting whirlpools of trash we’ve riddled our bountiful body of water with. However, a recent, unexpected, almost random discovery by a team of Japanese scientists might just represent the light at the end of the tunnel our oceans so profoundly deserve.

The team of researchers, spearheaded by Shosuke Yoshida, was busy screening the natural microbial environment that surrounded climates rich in Polyethylene terephthalate (PET), a key component of the great majority of the world’s plastic products. While they analyzed the bacterial environment outside a bottle-recycling facility, they found a strain of bacteria that seemed able to feed off the monstrous amounts of PET that the facility made so immensely available. The bacteria their study identified, Ideonella sakaiensis, uses PET as its primary energy and carbon source, essentially “yielding the basic building blocks for growth”. 

The discovery came as a shock in 2016, as it provided evidence that “biodegradation of plastics by specialized bacteria” was suddenly within reach, as the researchers themselves communicated. Once the strain was identified, the scientists knew exactly where to look next. If the bacteria are able to essentially digest plastic, it must have some kind of digestive enzyme that makes the process possible. Enzymes are essentially the catalysts that make all digestion possible: they take in the complex chemicals from food, and convert them to the basic components that we can, in turn, assimilate within our internal biochemistry. All there was to do, then, was to identify and isolate the enzymes that made PET digestion possible within this particular strain of bacteria, in hopes of applying it, on a much larger scale, as a bioremediation strategy to rid us of the excess plastic that plagues our environment. 

Yoshida and his team found two enzymes fundamental to Ideonella sakaiensis’ ability to break down plastic, which work together to “convert PET efficiently into its two environmentally benign monomers, terephthalic acid and ethylene glycol.” Two years from the groundbreaking discovery that marked 2016, multiple groups of researchers scattered across the globe are working towards popularizing and optimizing the enzyme, which they now refer to as PETase. A study to be published in the coming weeks in the Proceedings of the National Academy of Sciences, subjected PETase to the powerful x-rays of the UK’s Diamond Light Source. Illuminating the enzyme with beams 10 billions times brighter than the sun’s, revealed, as expected, the molecular structure of the particular enzyme, broken down to our most precise level of understanding: the atom. The gif below, released directly by Diamond Light Source, highlights the peculiarities of its composition. Having understood its molecular complexities, the scientists enforced some mild changes to the structure, in order to compare it to that of other known enzymes in its massive database. In doing that, the team of researchers created a variant of PETase exhibiting a 20% improvement in PET degradation. Breaking down PET using this new variant of the enzyme takes only a few days, compared to the half millennium required for its natural degradation, a figure that might prove fundamental to our planet’s environmental future. 

This secondary team of researchers, led by co-author Gregg Beckham, have already begun the process of filing a patent for the enzyme, promising stable activity in temperatures above 70 Celsius. At these elevated temperatures, which roughly equal 160 degrees Fahrenheit, PET begins to melt, making the enzyme’s job a quantifiable “10 to 100 times faster”. The hope of the multiple research groups tackling this issue in different areas of the globe is that of installing what is essentially a massive hot water bath system that “is able to take PET bottles in a large reactor and break them down rapidly to their building block constituents.”

What that means for the world, largely, is the viable possibility of breaking down PET non-mechanically, in a process that returns PET’s non-harmful singular components. That might not sound all that exciting. However, it does mean that, by retrieving those singular components, we can remake the plastic we just destroyed. It would provide us, for the first time in history, the ability to engage in “full bottle-to-bottle recycling”, a technical way of conveying that the entirety of the plastic we use becomes, essentially, recyclable. In other words, it moves us ever closer to the coveted goal of “net zero”, which essentially means we can reuse and remodel all of the plastic the enzymes break down, in a loop that seems positively endless. 

It’s absolutely vital to understand that the brilliant scientific process this discovery embodies forms a bioremediation strategy. That is, it formulates a process for us to remedy the massive environmental damage we’ve pushed on our environment. It should, by no means, be mistaken as a solution to our environmental woes, or as an excuse to produce and consume plastic in excess, but rather as a way to constructively ameliorate our self-inflicted plastic plague. The innovation, remarkably, comes from nature’s own evolutionary adaptation to a man-made problem. We didn’t craft this enzyme, natural selection did, out of little else but necessity. It might be time for us to take inspiration from the same evolutionary principles that put us in control of planet Earth in order to preserve its (and our) well being, starting from the clean up of the disgusting patches of plastic that plague our oceans.