A superenzyme that degrades plastic bottles six times faster than before was created by scientists and could be used for recycling within a year or two.
The superenzyme, derived from bacteria that have naturally developed the ability to eat plastic, allows for complete recycling of the bottles. Scientists believe that combining it with enzymes that break down cotton could also allow blended-fabric garments to be recycled. Today, millions of tons of such clothing are dumped in landfills or incinerated.
Plastic pollution has contaminated the entire 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 components to make new ones from old ones, which means that more new plastic is created from oil every year.
The superenzyme was engineered by linking two separate enzymes, both found in the plastic-eating insect discovered at a Japanese waste site in 201
“When we linked the enzymes, quite unexpectedly, we got a noticeable increase in activity,” said prof. John McGeehan, from the University of Portsmouth, UK. “This is a trajectory towards trying to produce faster enzymes that are more industrially relevant. But it’s also one of those stories about learning from nature and then taking it to the lab. “
French company Carbios revealed in April a different enzyme, originally discovered in a compost leaf pile, which degrades 90% of plastic bottles within 10 hours, but requires heating above 70 ° C.
The new superenzyme works at room temperature, and McGeehan said the combination of different approaches could accelerate progress towards commercial use: “If we can create better and faster enzymes by linking them together and supplying them to companies like Carbios, and working in partnership, we could start doing it within the next year or two. “
The 2018 work established that the structure of an enzyme, called PETase, can attack the hard, crystalline surface of plastic bottles. They found, by chance, that a mutant version worked 20% faster. The new study analyzed a second enzyme also found in Japanese bacteria that doubles the rate of breakdown of chemical groups released by the first enzyme.
Bacteria that break down natural polymers such as cellulose have developed this dual approach over millions of years. Scientists thought that by linking the two enzymes together, they could increase the rate of degradation and allow them to work more closely together.
The linked superenzyme would be impossible for a bacterium to create, as the molecule would be too large. Then the scientists linked the two enzymes in the lab and saw a further tripling of the speed. The new research by scientists from the University of Portsmouth and four US institutions was published in the journal Proceedings of the National Academy of Sciences.
The team is now looking into how to modify the enzymes to make them work even faster. “There is huge potential,” McGeehan said. “We have several hundred of them in the lab we are currently running together.” A £ 1 million test center is now under construction in Portsmouth and Carbios is currently building a plant in Lyon.
Combining the enzymes that eat plastic with existing ones that break down natural fibers could allow for complete recycling of the blended materials, McGeehan said. “Mixed fabrics [of polyester and cotton] they are really difficult to recycle. We talked to some of the big fashion companies that produce these fabrics, because right now they are really struggling. “
Activists say reducing the use of plastics is key. Those who work on recycling say that strong and lightweight materials like plastics are very useful and that real recycling is part of the solution to the pollution problem.
Researchers also managed to find insects that eat other plastics such as polyurethane, which is widely used but rarely recycled. When the polyurethane breaks down, it can release toxic chemicals that would kill most bacteria, but the identified insect actually uses the material as food to power the process.