Few materials have impacted the modern era as much as plastic. It is lightweight, durable, and cheap to produce; it’s become a vital part of everyday life. It’s in water bottles, shopping bags, food packaging, and, unfortunately, our environment. Plastic pollution is one of the world’s most persistent pollution problems. Vast amounts of discarded plastic gather in our oceans, threatening marine life. Fortunately, scientists have found an enzyme with a Pac-Man-like appetite for plastic.
Researchers from the University of Konstanz have discovered a curious enzyme that can digest certain polyesters and biodegradable plastics. Not only can it eat plastics, but it can also break down penicillin, suggesting a possible effect on antibiotic resistance. The enzyme was dubbed the Pac-Man enzyme due to the wide active site, the opening where the reaction takes place, in the molecular structure. This shows that bacteria have adapted to digest certain plastics more rapidly than scientists speculated.
Biologists Harry Lerner and David Schleheck found these enzymes in an attempt to learn whether microbial communities could break down long-chain aliphatic polyesters (LCAPs). “We buried small pieces of LCAP bioplastic film in the upper humus layer in the forest at the university’s botanical garden, about ten centimeters deep,” Lerner explained. The humus layer is the layer of soil containing the greatest amount of decaying organic matter, meaning it is rich with microorganisms to observe. They repeated the experiment with different kinds of plastic: cellulose, other biodegradable plastics, and conventional polyethylene plastic. After a year of being buried and undisturbed, they discovered that the bioplastic had completely broken down, while the polyethylene remained intact. These results showed the importance of the chemical composition of the plastic, which can affect whether or not the enzymes can attack and break the bonds of some polymers. Additionally, after further investigating the structure of these enzymes, the scientists found a striking similarity to that of bacteria resistant to antibiotics, like penicillin. This hints at the enzyme’s dual biochemical function — breaking down polyesters into monomers on the one hand and cleaving penicillin on the other.
Plastic remains one of the most frequent pollutants in our environment, with 57 million tons of plastic pollution every year. The discovery of the Pac-Man enzyme is a big step in regulating the world’s plastic pollution problem. While it’s not a one-and-done solution to our problem, it does show the importance of switching to biodegradable plastics and how it might put a dent in that huge statistic. For now, the battle with pollution persists, but at least we found something willing to eat our plastic; tiny as it may be, Mother Nature fights on.
