Plastic, as we all know, is a menace to the environment. In recent years, the problem of plastic pollution has escalated quite drastically, causing cities, towns and even oceans to be clogged with this harmful substance. Last year, a team of scientists from Stanford University and Beijing-based BeiHang University demonstrated the amazing Styrofoam-digesting abilities of mealworms. As part of a somewhat similar study, another group of researchers has found a species of bacteria that literally feeds on plastic waste.
Of the 33 million tons of plastic discarded every year in the United States alone, a large portion (35 billion to be exact) is in the form of plastic bottles. According to scientists, polyethylene terephthalate (PET), the kind of plastic commonly used to make water bottles, is also the main constituent of polyester clothing, blister packaging, frozen-dinner trays, food packaging such as peanut butter jars, salad containers, potato chip bags and so on. Talking about the environmental implications of plastic pollution, Tracy Mincer, a researcher at Massachusetts-based Woods Hole Oceanographic Institute, said:
If you walk down the aisle in Wal-Mart you’re seeing a lot of PET.
Known for being lightweight, strong and transparent, PET is highly resistant to decomposition by microbes. Although it has the highest recycle rate among all kinds of plastics, less than half of the products containing PET are actually recycled. It is also one of the most common pollutants, responsible for clogging oceans and other water bodies with plastic debris.
For the current research, a team of scientists from Japan’s Keio University and Kyoto Institute of Technology collected as many as 250 PET-contaminated soil, sediment and sewage water samples from recycling sites in the Japanese city of Osaka. These samples, according to the team, acted as substrates for bacteria and other microbes to grow. Upon screening them, the researchers discovered a host of microorganisms living on the polluted materials, causing the PET films to break down. Further analysis revealed that a specific species of bacteria, Ideonella sakainesis, was responsible for the biodegradation of the plastic.
As the scientists point out, the bacterium uses two different types of enzymes to break the PET molecules down, turning them into food in much the same way as the human body uses enzymes to break down ingested food. The process begins with the microbes colonizing the PET substrate, following which they secrete one particular enzyme to decompose the plastic particles into an intermediate chemical. The resultant chemical is then absorbed by the bacterial cells, where it is disintegrated even further by a second enzyme. This reaction, the team believes, provides the energy and carbon needed for the bacteria to grow.
As observed during laboratory testing, a small colony of I. sakainesis can completely break down a thin sheet of PET in around six weeks, provided the temperature remains constant at 86 degrees Fahrenheit. While the process is indeed a bit slow, the researchers believe that the breakthrough could one day help reverse plastic pollution. Speaking about the research, recently published in the Science journal, Mincer added:
When I think it through, I don’t really know where it gets us. I don’t see how microbes degrading plastics is any better than putting plastic bottles in a recycling bin so they can be melted down to make new ones…This process could be quite common. Now that we know what we are looking for, we may see these microbes in many areas around the world.