Plastics are everywhere. Once they get into the environment as trash, they stay there for years, decades, or even centuries. That’s because most plastic is chemically inert and immune to the enzymatic processes involved in biodegradation. We’ve tried to curtail plastic pollution through recycling and by creating plastics that are biodegradable or compostable. But what about all the plastic litter that’s already out there and could persist long after our grandchildren are gone?

Life may be coming to our aid. A team of scientists in Japan, led by Shosuke Yoshida of Kyoto University, has recently discovered a species of bacteria that can degrade a plastic called PET.

Identifying microbes that degrade PET

PET stands for polyethylene terephthalate, a plastic with good mechanical, barrier, and optical properties. Bottles for water and soft drinks are just a couple of PET’s many, many uses. PET is a polyester compound with a high aromatic content, which makes it chemically inert. As a result, it is typically considered resistant to microbial degradation, although certain fungi grow on a mineral medium containing PET. Roughly 56 million tons of PET are produced each year, and a lot of that ends up in the environment.

To see whether organisms other than a few fungi can manage to digest this plastic, Dr. Yoshida and his team screened 250 PET debris-contaminated environmental samples. These samples originated in everything from sediment to wastewater. The scientists looked for microorganisms that could use low-crystallinity (1.9 percent) PET film as a major carbon source for growth.

The team identified a distinct microbial consortium that, once cultured, was able to grow on PET. The PET film surface degraded at a rate of 0.13mg per square centimeter each day at 30°C. Under similar conditions, the organisms turned 75 percent of the carbon it obtained from the PET into CO₂.

Identifying the enzymes that break down PET

Currently, there are few known enzymes capable of breaking down PET through a chemical process known as hydrolysis. In order to determine what enzymes:-

1. sakaiensisuses, the scientists sequenced its genome. They identified one gene, ISF6_4831 that encodes a protein that shares half of its amino acids with another enzyme that hydrolyzes PET. The area of similarity includes the parts of the enzyme that are used for catalytic activity.