Researchers from the United States and Britain accidentally engineered an enzyme that eats plastic.
In studying the plastic-eating enzyme that the bacterium produced, they were looking at how the enzyme evolved - in the process, a tweak to the enzyme revealed that they had inadvertently made it even better at breaking down the bottle plastic, PET (polyethylene terephthalate).
At the moment PET takes hundreds of years to break down in the natural environment and is a major contributor to land and sea pollution.
The new research sprang from the discovery of bacteria in a Japanese waste recycling centre that had evolved the ability to feed on plastic. By shining intense beams of X-rays on it, 10 billion times brighter than the sun, they were able to see individual atoms.
Scientists have discovered that an enzyme exists that breaks down plastic components in a matter of days, and there is hope that it could be utilised to alleviate the global plastic disposal issue. Using their beamline I23, an ultra-high-resolution 3D model of the PETase enzyme was generated in exquisite detail. To test this theory, the researchers mutated the PETase and that was when the unexpected happened.
The researchers found that the PETase mutant was better than the natural PETase in degrading PET.
'It means we won't need to dig up any more oil and, fundamentally, it should reduce the amount of plastic in the environment'.
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Once they understood its structure, the team noted that they could improve the performance of PETase by adjusting a few residues on its surface.
The researchers say the PETase mutant enzyme could also be used to degrade polyethylene furandicarboxylate (PEF, ) which is a newer polymer that's being increasingly used to make bottles. These differences indicated that PETase must have evolved in a PET-containing environment to enable the enzyme to degrade PET.
"The engineering process is much the same as for enzymes now being used in bio-washing detergents and in the manufacture of biofuels - the technology exists and it's well within the possibility that in the coming years we will see an industrially viable process to turn PET and potentially other substrates like PEF, PLA, and PBS, back into their original building blocks so that they can be sustainably recycled", says McGeehan.
"It is a modest improvement - 20% better - but that is not the point", said McGeehan.
The team's goal is to use their findings to continue to improve the new enzymes to break down these man-made plastics, but in a fraction of the time. "It is so easy for manufacturers to generate more of that stuff, rather than even try to recycle".
The discovery could be a step toward eliminating the huge swaths of plastic waste often found floating in oceans or washed up on beaches all over the world, the researchers said. Scientists claim to have created mutants that eat plastic bottles. The Portsmouth University team, and their collaborators, the US National Renewable Energy Laboratory in Colorado, have since filed for a patent.