From the Managing Editor's Desk
Dan Bolton,STiR managing editor
Eons ago, plants developed the ability to gird their leaves in a new flexible material of long-chain polymers synthesized from self-made oil and the energy of the sun.
Plants invented plastic.
The high molecular weight leaf coating acts as a moisture barrier, reducing the danger of dehydration and offering protection from pathogens. In an evolutionary move to thwart the new defense, bacteria excreted new chemicals to unlink the polymer chains, making it possible to gobble the tasty leaves.
In the 1993 movie, Dr. Ian Malcolm, played by actor Jeff Goldblum, questioned Jurassic Park c.e.o. John Hammond (portrayed by Richard Attenborough) on the venture’s ability to control life.
“It’s not possible,” says Malcolm, “If there is one thing the history of evolution has taught us it’s that life will not be contained. Life breaks free, it expands to new territories and crashes through barriers, painfully, maybe even dangerously… life finds a way.”
The discovery of a newly evolved plastic-dissolving bacteria that can digest mankind’s glut of PET (polyethylene terephthalate) is a fortunate example of this principle at work. PET is a strong thermoplastic commonly used to make bottles. Since the 1970s manufacturers have converted petroleum compounds into what is now 45 million metric tons of plastic annually (9.2 billion tons since 1950). Unfortunately, only 30% of PET is recycled. Each new bottle reduces the world’s supply of oil.
Versatile and inexpensive, PET is an ideal plastic―except for the fact that it takes hundreds of years to break down in the environment. That is why researchers were baffled to find pools of PET monomers, the building blocks for this plastic, at the bottom of a landfill in Sakai, Japan. In 2016 scientists at the Kyoto Institute of Technology isolated a new bacterium from the mix, naming it idionella sakiensis. This bacterium produces enzymes that degrade PET. They named this plastic-eating enzyme PETase. At modest temperatures, 86o F (30o C), PETase dissolves the links in the long chains of molecules that make up plastic, reducing tough plastics like PET to their basic components.
These are not the potentially dangerous nanoparticles of plastic increasingly found in water supplies and even fish, a byproduct of environmental erosion of PET.
The remarkable discovery of PETase makes possible a “regenerative” cycle more efficient than recycling. PET may soon be digested in vessels by bacteria that give off CO2 and leave a pool of ethylene glycol and terephthalic acid—the building blocks of virgin plastic.
“This could provide huge savings in the production of new polymer without the need for petrol-based starting materials,” notes Uwe T. Bornscheuer, an enzyme catalysis expert at the University of Greifswald, in a commentary that accompanied the initial study.
Last month scientists from the University of Portsmouth, in collaboration with the U.S. Department of Energy’s National Renewable Energy Laboratory, announced they had developed a mutant of the bacterium that degrades PET even faster and also digests PEF, a plastic used to make fibers.
Professor John McGeehan, who was involved in the development, told the BBC that "[PET] has only been around in vast quantities over the last 50 years, so it's actually not a very long timescale for a bacteria to have evolved to eat something so man-made."
McGeehan, director of the Institute of Biological and Biomedical Sciences at Portsmouth said the team exploring enzyme production accidentally engineered the more efficient PETase.
"Serendipity often plays a significant role in fundamental scientific research and our discovery here is no exception," said McGeehan.
Life finds a way.