Plastic Waste Management’s Ace in the Hole: The Discovery of a Bacterium Eating Plastic

Post date:2019.08.09

G20 summit in Osaka has concluded with the adoption of “G20 Osaka Leaders Declaration” on June 29. In the declaration, a new goal which reduces additional marine plastic litter to zero by 2050 was set.

Many plastic products, such as bags, food trays, straws, and cups, are used daily. Each plastic waste is disposed as combustible wastes, or crushed as non-burnable garbage, or utilized as a recycled resource. 8.3 billion tons of plastic wastes have been produced since 1950, and 6.3 billion tons of them have been dumped. Just 9% of these plastics have been recycled. 79% of the plastic wastes have been buried in landfills or thrown away in the ocean. However, it takes 20 and 50 years to break down a plastic bag and a cup of Styrofoam, respectively. Once these plastics are discharged to the environment, they become microplastics, particles of less than 5mm and this is due to UV radiation and mechanical erosion. With their smaller size, they can be easily ingested by sea creatures, thus being contaminated with the chemical pollutants present in the particles. Furthermore, it is also concerned that they will be taken into our bodies through eating some fish.

In Japan, 9.4 million tons of plastic wastes are produced every year, and 25% of them are recycled, 57% of them are recovered as heat, and 18% of them are unutilized or just disposed. After China had banned importing plastic wastes, our country has changed the destination for export to Southeast Asian countries like Thailand. However, we will become unable to export them to such countries in the future due to the amendment of the Basel Convention, which will take effect in January 2021. In the first place, considering that those countries have no advanced disposing facility, the problem is that we take initiative in environmental destruction through forcing our wastes in exchange for money. We need to urgently take measures to dispose them domestically.

Recently, some of our familiar environmental efforts have been promoted. Some fast-food restaurants are switching to paper straws instead of plastic, and some supermarkets provide plastic bags for a fee. However, it is not enough to solve the problem. Drastic measures are required.

According to the newspaper on June 21, 2019, a group of Japanese researchers had discovered a bacterium that gorges on PET bottles, and that can be harnessed in the resolution of the plastic problem.

Ideonella sakaiensis, which was found in soil samples in Osaka, Japan, can not only break down plastic poly ethylene terephthalate (PET) but also increase its number by using PET as nutrition. Two enzymes, PETase and MHETase, included in the bacterium can hydrolyze PET to terephthalic acid and ethylene glycol, which are broken down further to produce carbon dioxide and water. “We would be able to propose a low-energy, environmentally friendly strategy for biological recycling of PET waste products”, the researcher mentioned in the report in 2016. If the bacterium itself or PETase and MHETase are put into practical use, it might shed some light on the plastic problem.

Potential ability of various bacteria has surprised us. They are sometimes seemed to be dependable for us from the aspect of their various unknown functions. I would like to introduce their multiple functions continuously through my future columns.