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Plastics waste – no problem; scientists develop enzymes to break down PET in weeks

Petrochemical industry | 22 Mar 2022 17:43 IST | Polymerupdate.com

With an admissible lifespan of around 450 years, plastics, the wonder material of the sixties and seventies, have become a cause of major concern for the entire world due to irresponsible dumping of its waste, which has started posing a very real environmental threat to our planet.

According to reports, around 275 million tonnes of plastics waste is generated each year around the world of which a quantity between 4.8-12.7 million tonnes finds its way into the sea, thus causing air, water, and soil pollution. Policymakers across the world have been drafting rules for several years with a ban on single-use plastics in many countries and extended producers’ responsibility (EPR) among others, to reduce irresponsibly dumping of plastics waste into the environment. Unfortunately, no visible progress has been achieved yet.

But now, scientists have developed enzymes that can break plastics waste in a matter of weeks. Reports said that researchers at the University of Portsmouth, United Kingdom, succeeded in engineering a better-performing version of enzymes called ‘MHETase’ to form a super enzyme that digests hard plastics like polyethylene terephthalate (PET) at six times the speed.

In 2016, scientists in Japan had discovered a bacterium with a natural appetite for PET plastics, using enzymes to break it down in a matter of few weeks. Later a better performing version of this enzyme was discovered in 2020 which was called ‘PETase’. Now, when PETase is combined with a super enzyme called ‘MHETase’, PET plastics can be digested at six times the speed of the previous version of enzymes.

“Over the past five years, scientists have succeeded in getting some breakthroughs, demonstrating how enzymes can be used to break down common plastics such as the PET which finds application in a water bottle to shampoo containers. In pursuit of a circular economy for plastic waste, scientists have now discovered a new enzyme that further breaks down one of the key plastic building blocks left behind by this process, leaving thereby simple molecules that can be repurposed for use in new products,” said the report.

In this process, two chemical building blocks of PET have left ethylene glycol (EG) and terephthalic acid (TPA), and one is more problematic than the other. While EG is a chemical with many applications – it’s a part of the antifreeze used in cars, TPA does not have many uses outside of PET. Most importantly, TPA has nothing that most bacteria can even digest. But, an enzyme from PET-consuming bacteria recognizes TPA like a hand in a glove. The study then demonstrated that this enzyme, called TPADO, breaks down TPA with amazing efficiency,” said Professor Jen DuBois, the study editor.

In the last few years, there have been incredible advances in the engineering of enzymes to break down PET plastic into its building blocks. The new enzyme goes a stage further that looks at the first enzyme in a cascade that can deconstruct those building blocks into simpler molecules. These can then be utilized by bacteria to generate sustainable chemicals and materials, essential for making valuable products out of plastic waste.

It is, however, unclear whether this enzyme can be developed on a commercial scale. But, given that researchers continue their efforts to discover a solution to the plastics waste problem, a breakthrough can be achieved in the visible future.



DILIP KUMAR JHA
Editor
dilip.jha@polymerupdate.com
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