By Damian Carrington / The Guardian / Sept. 28, 2020
A super-enzyme that degrades plastic bottles six times faster than before has been created by scientists and could be used for recycling within a year or two.
The super-enzyme, derived from bacteria that naturally evolved the ability to eat plastic, enables the full recycling of the bottles. Scientists believe combining it with enzymes that break down cotton could also allow mixed-fabric clothing to be recycled. Today, millions of tonnes of such clothing is either dumped in landfill or incinerated.
Plastic pollution has contaminated the whole planet, from the Arctic to the deepest oceans, and people are now known to consume and breathe microplastic particles. It is currently very difficult to break down plastic bottles into their chemical constituents in order to make new ones from old, meaning more new plastic is being created from oil each year.
The super-enzyme was engineered by linking two separate enzymes, both of which were found in the plastic-eating bug discovered at a Japanese waste site in 2016. The researchers revealed an engineered version of the first enzyme in 2018, which started breaking down the plastic in a few days. But the super-enzyme gets to work six times faster.
“When we linked the enzymes, rather unexpectedly, we got a dramatic increase in activity,“ said Prof John McGeehan, at the University of Portsmouth, UK. “This is a trajectory towards trying to make faster enzymes that are more industrially relevant. But it’s also one of those stories about learning from nature, and then bringing it into the lab.”
French company Carbios revealed a different enzyme in April, originally discovered in a compost heap of leaves, that degrades 90% of plastic bottles within 10 hours, but requires heating above 70C.
The new super-enzyme works at room temperature, and McGeehan said combining different approaches could speed progress towards commercial use: “If we can make better, faster enzymes by linking them together and provide them to companies like Carbios, and work in partnership, we could start doing this within the next year or two.”
The 2018 work had determined that the structure of one enzyme, called PETase, can attack the hard, crystalline surface of plastic bottles. They found, by accident, that one mutant version worked 20% faster. The new study analysed a second enzyme also found in the Japanese bacteria that doubles the speed of the breakdown of the chemical groups liberated by the first enzyme.
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No comments about this? The thing that stood out to me is that I’m breathing in micro-particles of plastic! I’m old enough to remember when plastic was still considered a minor miracle. Before the Era of single-use water & soda bottles. I remember thick glass bottles containing cough medicine & children’s (liquid) antibiotics. When dropping the mayo or peanut butter meant a huge greasy mess, filled with glass shards, to clean up. For some uses it’s
now indispensable.
But our bottled drinks are just the more publicized problem. Unfortunately I’ve had many hospitalizations & the amount of plastic waste is unbelievable! As an asthmatic, I usually take the tubing, etc. home with my nebulizer. But your oxygen mask or nasal cannula, your needles, the water pitcher & cup & many other items are tossed after use, if not at the time, they’re mostly discarded when you go home. I’m not saying they should be re-used; I wouldn’t want to use someone else’s cannula, but talk about single-use!
I live in North County & EDCO has authorized reycling of any plastic item that can hold its shape. A few years ago they added (clean) styrofoam to the recyclable list. Presumably that means that somewhere there is a market for it. On a side note: China buys a lot of our plastic drink containers. With them making so many of the items we buy, I guess they’re putting it all to use. But I did hear, probably within the ladt year, that they had stopped buying it, don’t know what the situation is at present. At any rate, the micro bits of plastic in the ocean & its fish are proof that recycling has not solved the problem. (Pacific Garbage Patch sound familiar?) Here’s a possible new job category: inspectors to randomly check the bins on trash day & cite those who have recyclables in their actual trash. Heck, that would require a whole department with support staff to mail out the notices (although these could be left on the bin or on the front door of the offending party) & answer calls that are generated by the receipt of a ticket, plus routing of the paid fines & following up on unpaid fines.
That said, it still does not cover places like apartment buildings & offices.
I suppose there are countries where the trash problem is worse, but when have you ever heard of someone getting a ticket for littering on the freeway? There’s a reason people sign up to clean up a portion thereof! I don’t think anyone sees the signs, much less fears getting a ticket for it. I guess those who love their single-use bottles can rejoice, but as great as this news is, it doesn’t come close to solving the problem. Still, we have to start somewhere!