SOURCE: Austin, H. P., Allen, M. D., Donohoe, B. S., Rorrer, N. A., Kearns, F. L., Silveira, R. L., … & Mykhaylyk, V. (2018). Characterization and engineering of a plastic-degrading aromatic polyesterase. Proceedings of the National Academy of Sciences, 201718804. DOI: 10.1073/pnas.1718804115
Plastic, plastic, everywhere
Plastics have been around for less than 100 years, but have become essential to society. Because plastics are versatile and have low production costs, they are now found everywhere, even a remote island in the South Pacific with no human inhabitants. While plastics make our lives easier, they are also a global pollution threat.
Poly(ethylene terephthalate) or PET is the most abundantly produced plastic. It is used in single-use beverage bottles, clothing, packaging and carpeting. The properties that make PET useful to us also make it resistant to degradation in the environment. This means that PET can last centuries in the environment. Why not recycle it? PET can be broken down into its components using chemicals, but this process is very expensive compared to the cost of new PET. Sometimes PET is recycled mechanically, but the recycled PET product loses value because it doesn’t have the same properties as original PET. As a result, PET often makes its way to landfills or escapes into the environment where it can last for years.
Can bacteria help?
A group of scientists previously discovered a tiny creature known as a bacterium. The name of this bacterium is Idenoella sakaiensis 201-F6 and it has the rare ability of using PET as its major carbon and energy source for growth. In other words, this bacterium can eat plastic. Scientists hypothesized that bacteria might be evolving to partially degrade manmade plastics that are quickly accumulating in the environment.
Researchers in this study wanted to examine the enzyme called PETase that allows the I. sakaiensis bacteria to consume plastic. A better understanding of how the enzyme works could help us to use it in plastic recycling. The scientists used X-ray crystallography to create a diagram of the enzyme (Figure 2). They also ran tests to determine if PETase could degrade other types of plastics. The scientists discovered that the bacteria could eat another type of plastic called poly(ethylene furanoate) or PEF. PEF is an emerging bio-based PET replacement, but like other plastics, its lifetime in the environment is likely to be quite long.
What’s the big deal?
We now know a bacterium can use PET as a major carbon and energy source using the PETase enzyme. Future scientists can utilize the information gathered in this study to further engineer PETase so that it can be used to break down the plastic accumulating in nature. Much of that plastic makes its way into our oceans. Scientists estimated that in 2010, 4.8 to 12.7 million metric tons of plastic entered the ocean. Many organizations recognize this problem and significant efforts are underway to clean up plastic pollution. These ideas range from banning plastic bags to creating new machines to collect plastic in rivers and oceans. Unfortunately, some of these methods are expensive and difficult to perform on a large scale. This study highlights that PETase could be an alternative or used in combination with ongoing efforts to help fix our plastic pollution problem.
Do you want to help? This link provides 10 easy steps you can take to help reduce plastic pollution.