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A Plastic-Eating Enzyme

Paul Kando

Around 8% of the world's oil production is used to make plastics, yet only 5% of the plastics produced are recycled. Plastic soda, water, and juice bottles are almost never made from recycled plastic, and the plastic bottles that do get recycled can only be turned into carpets or similar products.

Pacific Garbage Patch
photo credit: Inner Self

Plastics have become a pestilence. They spread across our world as computer keyboards, mice, printers, monitors, TVs, packaging, disposable dishes and utensils, tiny plastic beads used in toiletries like facial scrubs and toothpastes, and more. About one million plastic bottles are purchased around the world every minute, a number predicted to increase 20% by 2021.

According to Ecowatch, more plastic was produced over the last ten years than during the whole of the last century. Half of all plastic is used just once before being thrown away. The average American tosses 185 pounds of plastic — including some 120 bottles — every year. Approximately 500 billion plastic bags are used worldwide annually — more than one million every minute.

Some 10% of the waste-stream is plastic. In the Los Angeles area alone 10 metric tons of plastic objects are washed into the Pacific every day. There they break into small pieces, many of which float for years before concentrating in ocean gyres. In Lake Erie, researchers found up to 1.7 million plastic particles per square mile — 85% of them smaller than 2/10 of an inch, Plastic makes up about 90% of all floating garbage — some 46,000 pieces per square mile of ocean surface. The Great Pacific Garbage Patch is the world’s largest. Twice the size of Texas, it floats in the North Pacific Gyre off the California coast, Floating plastic pieces now outnumber sea life six to one. 44% of all seabird species, 22% of cetaceans, all sea turtle species plus a growing list of fish have been found with plastic inside or wrapped around their bodies. One million sea birds and 100,000 marine mammals are killed annually by plastic.

The chemicals in plastics can be absorbed by the human body and can alter hormones or have other health effects. 93% of Americans age 6 or older test positive for Biphenol A (BPA), a plastic chemical. It takes 500 to 1,000 years for plastic to degrade. Bioplastics are a poor substitute — they require food crops as raw material.

But there is a ray of hope. As reported in the Proceedings of the National Academy of Sciences, researchers from Britain’s University of Portsmouth and the U.S. National Renewable Energy Laboratory made an accidental discovery while examining the structure of a natural enzyme thought to have evolved in a waste recycling center in Japan. The enzyme Ideonella sakaiensis is able to help certain bacteria slowly digest polyethylene terephthalate (PET) — a thermoplastic material, “polyester”, patented in the 1940s. Now used in billions of plastic bottles. PET can persist in the environment for hundreds of years and currently pollutes large areas of land and sea worldwide.

The enzyme’s digestion was slow, Could it be speeded up? Non-toxic and biodegradable enzymes can be produced in large amounts by microorganisms. Could they be “tweaked” using technology, and eventually be used to break down the most commonly used plastics? Such questions prompted the research team to experiment with Ideonella Sakaiensis’ molecular structure. To their pleasant surprise, doping with amino acids made the enzyme break down the PET much faster — in just a few days. And this modified enzyme — the scientists christened it PETease — may even be optimized further.

Needless to say, the enzyme’s development as a pollution-solution is at a very early stage. Even so, independent scientists not directly involved with the research are finding it hopeful. The team is now working to create an industrially viable process to break down PET — and potentially other plastic polymers — into their monomer building blocks, making it possible for them to be sustainably recycled.

Discoveries like PETease bring us closer to the important goal of sustainably recyclyng polymers. PETease essentially reverses the manufacturing process by reducing polyesters back to their building blocks which can be used again. This new finding promises a way to turn old plastic bottles into new ones, using recycled plastic to make new plastic — potentially eliminating the need for oil as raw material and reducing manufacturing energy as well. In this light PETease is a stunning discovery that could help fight the world's escalating plastic crisis.