Environment

Engineered "super-enzyme" gobbles plastic waste at six times the speed

Engineered "super-enzyme" gobb...
Hundreds of millions of tons of PET plastics are produced for things like water bottles each year, but a newly-engineered "super-enzyme" could help tackle the problem
Hundreds of millions of tons of PET plastics are produced for things like water bottles each year, but a newly-engineered "super-enzyme" could help tackle the problem
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Hundreds of millions of tons of PET plastics are produced for things like water bottles each year, but a newly-engineered "super-enzyme" could help tackle the problem
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Hundreds of millions of tons of PET plastics are produced for things like water bottles each year, but a newly-engineered "super-enzyme" could help tackle the problem

Back in 2018, scientists in Japan made the key discovery of a bacterium with a natural appetite for PET plastics. This raised the prospect of a low-cost solution to some of the most common forms of plastic pollution, and now scientists have used this bacterium as the basis for a newly engineered “super-enzyme” that can digest plastic waste six times faster.

Known as Ideonella sakaiensis, the bacterium discovered by scientists at the Kyoto Institute of Technology a couple of years ago showed a remarkable ability to use PET plastics as its energy source. These are the materials used to construct everything from soda to shampoo bottles, with hundreds of millions of tons produced every year, and the team was excited to find that the bacterium could completely break it down within a matter of weeks.

The bacterium was found to do so through a pair of enzymes, one of which, called PETase, was soon engineered in the lab by researchers from the University of Portsmouth and the National Renewable Energy Laboratory (NREL) to be around 20 percent faster at breaking down plastic than it was originally. Now, the same team has succeeded in combining it with its partner enzyme, called MHETase, to up the digestion rate even further.

The scientists achieved this by first studying the atomic structure of the enzymes with a synchrotron that uses X-ray beams 10 billion times brighter than the Sun. This serves as a microscope, allowing the team to solve their 3D structure and use these insights to engineer connections between the two enzymes. Simply combining the two enzymes doubled the speed of the plastic digestion, but engineering special connections between them resulted in a “super enzyme” that again increased the rate of plastic degradation by another three times.

“Our first experiments showed that they did indeed work better together, so we decided to try to physically link them, like two Pac-men joined by a piece of string,” says the University of Portsmouth’s Professor John McGeehan, “It took a great deal of work on both sides of the Atlantic, but it was worth the effort – we were delighted to see that our new chimeric enzyme is up to three times faster than the naturally evolved separate enzymes, opening new avenues for further improvements.”

Just like its predecessors, as the new super-enzyme digests PET plastics it returns the material to its original building blocks, which means the technique could be used as part of an infinite recycling loop. The original enzyme couldn’t do this fast enough to account for the huge amounts of PET waste generated around the globe each year, so producing an engineered version that increases the rate six-fold is seen as a significant step forward.

The research was published in the journal Proceedings of the National Academy of Sciences of the United States of America.

Source: University of Portsmouth

9 comments
carlesque
What if this new bacterium gets out into the wild? Could it start attacking plastics everywhere?
guzmanchinky
Incredible science. These are the people who will save our planet.
Synchro
Carlesque's "what if" exact scenario was played out in "Mutant 59: The Plastic Eaters" by Kit Pedler & Gerry Davis way back in 1972.
Kpar
carlesque, my thoughts, exactly. I remember reading a Larry Niven sci-fi novel in which an alien race attacked another alien race by using such, bringing down their civilization.

In true sci-fi fashion, it was a microbe that ate superconductors, but the principle is the same.
History Nut
Same thought, what if it got loose?
Aross
This may be a solution for the garbage that is out there already but the only real solution is to replace the plastic with a more environmentally friendly product. Glass for bottles and jars etc worked well for many years. They may be more costly to produce but are cleanable and reusable or crushable to be remade into the same products again. This seems to work well with beer bottles in Denmark where bottle were standardized to make the process simpler.
Karmudjun
carlesque - they are not re-engineering the bacterium they found this enzyme in, they have taken the bacterial DNA and have worked with it in the lab. They put it in specially trained surrogate bacteria whose genetic material is well known and then watch the host bacterium produce the product. Or the grad students do the work and then tell their mentors the findings. It would be interesting to know how many 'surrogate' bacterium have managed to get into the wild and produce insulin 'on the street'. Or the same with steroid production. And the thousands of other lab produced enzymes developed over the past 70-80 years. I cannot answer that question, but I can tell you that I am not worried about the prospects. Usually the 'surrogate' bacterium are fastidious and not robust enough to last long in the wild. But what if Ideonella sakaiensis mutates and somehow manages to upgrade it's own DNA to produce such an efficient enzyme? It would take a remake of "The Blob" to manage the secretion of enough to begin destroying PET anywhere close to your neighborhood - and I bet the local police will ignore the alarming calls until everyone's plastic road barricades and traffic cones begin to dissolve into the asphalt from the bottom upward. And heaven forbid if a bright sunny day with solar UV-C shining down onto these blobs wouldn't end up killing the bacteria out in the open! We'd then have to watch out for the creeping colonies of ideonella sakaiensis to infiltrate our sewer systems and eat the PET out of our toilet rings and plastic 'easy repair' couplings. You'll know it is happening by the smell of sewer gas........as the Joker liked to ask "Have you ever danced with the Devil in the pale moonlight?"

You understand the Joker was a biochemist- he knew moonlight reflected no UV-C onto the Earth so the bacterial DNA wasn't degraded in the moonlight.
WONKY CLERKY
I most strongly concur with the commenters other who have expressed high concern as to just wot would happen if the the bug broke free of lab'
. . . . ...... mmmmmm . . . ...... ? etc
Looking back Into the mirror of time, it is all reminiscent of when Hydroflouric acid was 'discovered' and concentrated . . . ...... mmmmmm . . . ......
BUT HF CAN'T REPRO' ITSELF.
ljaques
carlesque/kpar/synchro: ditto the oil-eating bacteria stories which ate civilization's output.