All Kerry MacKay wants for Christmas is an adorable population of enzymes and caterpillars that can break down plastic at a molecular level
ENVIRONMENT
Merry munching maggots
All Kerry MacKay wants for Christmas is an adorable population of enzymes and caterpillars that can break down plastic at a molecular level
The winter weather can put a bit of a downer on diving. Storms blow out dive plans and pile plastic litter on our shores. It’ s all a bit depressing. To brighten the mood a little, and in the hope of a pollution-busting miracle for Christmas, please allow me to introduce what could be the saviour of our plasticinfested world, the maggots.
Presenting the humble waxworm. The waxworm is actually not a worm, or even a maggot. It is the caterpillar( larval form) of a moth. It is called a waxworm because it lives in bee hives and eats the wax. You may have come across them as food for wild birds, pet reptiles, or bait for fishing.
Some pesky waxworms had invaded Dr Federica Bertocchini’ s beehives, so she put them into a plastic bag to transport them. Then she noticed they were making holes in the plastic. Not just biting through it but actually eating it!
Of course, this warranted further investigation. The scientists found that waxworm saliva contains enzymes that can break down plastic, even at room temperature. The chemical structure of wax happens to be quite similar to that of polyethylene plastic, aka the ubiquitous polythene plastic bag, floating in seas and eaten by turtles all around the world.
In even more positive news, there have actually been thousands of plasticdigesting enzymes identified. This is encouraging because there are many different types of plastic. Each different type of plastic needs different enzymes to break it down. For example, a bacteria from a cow’ s stomach can digest polyester.
Another bacteria, called Ideonella sakaiensis, found colonizing PET plastics in Japan, is receiving a lot of attention. This bacteria produces an enzyme named PETase, which appears to be able to break down PET plastic, such as the plastic bottles I often find littering dive sites. Scientists are working to engineer improved forms of this enzyme
“ Waxworm saliva contains enzymes that can break down plastic”
to make it more efficient. [ PET plastics, or polyethylene terephthalate, are widely used, recyclable thermoplastic polymers found in beverage bottles, packaging, and polyester fibres. Science Ed ]
PET, like most plastics, is currently difficult and expensive to recycle. Plastic recycling usually involves mechanical shredding, toxic chemicals, and requires high energy input. Even then, the result is poorer quality and cannot be recycled indefinitely.
Compounding this issue is the estimated 1 bin lorry worth of plastic waste being dumped into our oceans every single minute. It is difficult enough to recycle regular plastic, but these ocean plastics are often mixed with organic matter( seaweed, driftwood, algae), making it almost impossible to separate them for recycling.
Enzymes, however, break down plastics at a molecular level. The plastic compounds are split apart by the enzyme into smaller compounds. Just like our bodies use enzymes to break down
starches into sugars. Enzyme recycling could therefore potentially be a solution for these ocean plastic build-ups, as well as a means to deal with the vast quantities of microplastics we’ re pumping into our waterways.
By developing more efficient enzymes, the plastic recycling process could be sped up and require much less energy. There are also many things we could turn old PET plastic into, if these enzymes can be scaled up. Examples include flavourings, medications, textiles, and cosmetics.
For example, vanillin is a compound that creates the vanilla flavour we know and love from ice cream. These days, this is almost always a synthetic flavouring made from oil. When PET plastic is broken down by the PETase enzymes, we get the same raw materials as we would use from oil. This means we can make vanilla flavouring from old plastic!
Would you eat ice cream flavoured by old plastic bottles? Personally, I might at least allow the scent of recycled plastic vanilla to add to the warm, festive atmosphere in my home for Christmas. Especially if I know those enzymes are helping keep our oceans plastic-free. �
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