A superenzyme that breaks plastic bottles down six times faster than before has been developed by scientists and could be used for recycling in a year or two.
The superenzyme, which comes from bacteria that naturally developed the ability to eat plastic, allows the bottles to be fully recycled. Scientists believe that the combination with enzymes that break down cotton could also enable clothing made from mixed fabrics to be recycled. Today, millions of tons of such clothing are either dumped in landfills or incinerated.
Plastic pollution has contaminated the entire planet, from the Arctic to the deepest oceans, and humans are known to consume and breathe microplastic particles. It is currently very difficult to break down plastic bottles into their chemical components to make new from old, which means that more new plastic is made from oil every year.
The superenzyme was made by linking two separate enzymes, both found in the plastic eater that was discovered in a Japanese landfill in 201
“When we joined the enzymes together, quite unexpectedly, the activity increased dramatically,” said Prof. John McGeehan of the University of Portsmouth, UK. “This is one way of making faster enzymes that are more industrially relevant. But it’s also one of those stories about how to learn from nature and then bring it to the laboratory. “
The French company Carbios discovered another enzyme in April, originally discovered in a compost heap of leaves, which breaks 90% of plastic bottles within 10 hours but has to be heated above 70 ° C.
The new superenzyme works at room temperature, and McGeehan said that combining different approaches could accelerate progress toward commercial exploitation: “If we can make better, faster enzymes by linking them together and making companies like Carbios available and working in partnership , we could start working in the next year or two. “
The 2018 work found that the structure of an enzyme called PETase can attack the hard, crystalline surface of plastic bottles. They found out by chance that a mutated version worked 20% faster. The new study analyzed a second enzyme, also found in Japanese bacteria, that doubles the rate at which the chemical groups released by the first enzyme are broken down.
Bacteria that break down natural polymers such as cellulose have developed this dual approach over millions of years. The scientists thought that by combining the two enzymes this could increase the rate of breakdown and allow them to work more closely together.
The linked superenzyme could not be produced by a bacterium because the molecule would be too large. So the scientists connected the two enzymes in the laboratory and saw a further tripling of the speed. New research from scientists at the University of Portsmouth and four US institutions is published in the Proceedings of the National Academy of Sciences.
The team is now investigating how the enzymes can be optimized so that they work even faster. “There is great potential,” said McGeehan. “We have several hundred in the lab that we are currently holding together.” A £ 1m testing center is under construction in Portsmouth and Carbios is currently building a plant in Lyon.
By combining the plastic-eating enzymes with existing enzymes that break down natural fibers, mixed materials could be fully recycled, McGeehan said. “Mixed fabrics [of polyester and cotton] are really difficult to recycle. We spoke to some of the big fashion companies that make these textiles because they are really having problems right now. “
Activists say reducing plastic use is key. Those who work on recycling say that strong, lightweight materials like plastic are very useful and that real recycling is part of solving the pollution problem.
The researchers also managed to find insects that eat other plastics like polyurethane, which is widely used but is rarely recycled. When polyurethane breaks down, it can release toxic chemicals that would kill most bacteria. However, the identified bug actually uses the material as food to power the process.