Plastics play a key role in our lives; it’s used for packaging, clothing, cosmetics, transportation, communication, health care, etc. Currently, most plastic bottles are not truly recycled (they are melted and reformed into other hard plastic products). Packaging companies typically prefer freshly made plastics created from oil-derived materials. As I discussed in my previous post, it has become a huge problem for the global aquatic environment, but we still use it because plastic has many benefits, including its imperviousness to all known bacteria, which makes it great for food packaging…
But now, researchers have discovered a bacterium that can feed off of PET (polyethylene terephthalate), a plastic commonly used in plastic bottles and clothing fibers (PET is the most common thermoplastic polymer resin of the polyester family). This bacterium, called Ideonella sakaiensis, was found growing on PET debris in the fields around a recycling plant in Sakai, Japan.
Yoshida and his team were able to isolate I. sakaiensis and watched it degrade a plastic film in roughly 6 weeks. “This bacterium can degrade PET and then make their body from PET,” says the study’s lead reacher Shosuke Yoshida, according to NPR’s article. Even though plastic eating microbes have already been discovered (i.e., hard-to-cultivate fungi), this bacterium is special because it grows easily and quickly.
Most microbes cannot degrade the large plastic polymer chains, long thin molecules made of repeating carbon-based monomers, which are too big for individual microbes to take into its cell to metabolize. But Ideonella sakaiensis is unlike any other bacteria. Yoshida et al. were able to isolate the bacterium’s two enzymes- PETase and MHETase- that can slice the PET polymer into smaller pieces, which makes the polymer chains small enough for the bacterium to metabolize. Most of the chemicals made by this bacteria are consumed as food, but there are some byproducts such as terephthalic acid.
Yoshida and his team were able to show that these isolated enzymes alone could break down PET.
According to Yoshida via NPR, the bacteria isn’t very useful in the field (i.e. landfills) because it chomps very slowly. But with more research, this bacteria could potentially be genetically engineered and used to develop a bioremediation technology.
Perhaps the bacteria’s enzymes could be added to vats of plastics, where they would break down the plastics to release the terephthalic acid byproduct. If the terephthalic acid byproduct could be isolated, it could be reused to create “virgin” plastics and reduce the amount of oil needed to make the plastic in the first place.