Single-use plastic pollution, a massive issue that has been harming our planet’s environmental health for decades, might be able to be tackled with something as small as an enzyme.
Researchers Jen Dubois of Montana State University and John McGeehan of the University of Portsmouth have discovered enzymes that break down elements of single use plastic. These remarkable microbiological tools, called PETase and MHETase, have the ability to breakdown terephthalate polyethylene—one of the building blocks of (PET) plastic.
So, how does it work? How do these enzymes essentially eat plastic? PET is a polymer, which is a mega-protein made up of many smaller molecules (monomers). With the help of PETase and MHETase, these enzymes break the plastic down into “chemical building blocks”: ethylene glycol (EG) and TPA. Evidently now, a problem arises that concerns where these byproducts of the enzyme’s activity can go next. Thankfully, EG is a product that is useful for many everyday items, such as being an ingredient in antifreeze solution used in cars. But researchers can’t tell the same story for TPA; There is essentially no use for a chemical like this outside of PET plastic. So, with inspiration from the mechanism that made this byproduct in the first place, the Portsmouth research team thought the creation or discovery of another enzyme could do the job of breaking down TPA in the same way as for PET plastic.
Researchers from Michigan State University did just that, and found a solution to the overwhelming amount of TPA byproduct from PETase/MHETase activity of breaking down PET plastic. TPADO, an enzyme that breaks down TPA byproducts, was introduced, and was soon found to have incredibly binding ability to TPA—so much so that its fit into the chemical is described as “a hand in a glove.” In other words, the active site, the groove on the surface of the TPADO enzyme, fits perfectly with its substrate, TPA, by matching its exact shape, charge, and type of relationship with water (either hydrophobic or hydrophilic).
This groundbreaking research due to the collaboration of many researchers across several universities has revealed the long awaited light at the end of a very dark tunnel environmentalists call ‘the plastic crisis.’ With around 400 million tons of plastic discarded and then scoured all over the earth every year, the human race produces a weight of single-use plastic trash that is almost equivalent to the mass of the whole human population. But, with enzymes like PETase, MHETase, and now TPADO, modern science is now able to convert plastic waste into valuable molecular ingredients for other products, essentially minimizing waste in not only the plastic industry, but others, as well.
Still, these researchers’ jobs are not done, and they know it. TPADO has been tested under powerful x-rays to show its exact shape and molecular structure and reveal its innerworkings. With information like this, the world of enzyme engineering can be improved to make artificial ones that are more efficient and more useful.
So, something as small as enzymes can be the solution to the single-use plastic crisis we have here on planet earth? The answer is ‘yes’, thanks to modern science and dedicated researchers at the universities of Montana, Portsmouth, and Michigan State.
Image of single-use plastic waste.