VOLUME 31, ISSUE 2 SPRING 2022 PAGE 5
Science
Plastic-eating "super-enzymes": the key to the ecological crisis? By: Krisha Veera
O
nce prized for their durability, plastics now clog up oceans and pile up in heaps on land. Plastics take around 450 years to degrade in the ocean and even after this, they only break down into microplastics, remaining harmful to the environment. Hence, when scientists in Japan discovered bacteria that could “eat” plastic, the race to develop the most effective plastic-devouring bacteria began. The bacterial strain discovered can decompose a type of plastic called polyethylene terephthalate (PET). However, its efficacy isn’t nearly high enough to mitigate the tens of millions of tons of plastic waste that enter the environment every year. To make these naturally-occurring bacteria useful, scientists bioengineered the bacteria and increased its decomposition speed to a matter of weeks. In October 2020, this process was improved further by extracting two enzymes from this bacteria and combining them to produce a “super enzyme.”
The super enzyme combined the PETase and MHETase enzymes, allowing the breakdown of plastic up to six times faster than the previously bioengineered bacteria. The implications of this super enzyme are huge for recycling PET. PET is a type of plastic used in single-use drink bottles, carpets, and clothing, which naturally takes hundreds of years to degrade in the environment. With the super enzyme, it can be broken down into its building blocks in only a few days. These breakthroughs make it possible to see the super enzymes in industrial-scale facilities, used on piles of landfill-bound plastic or on the mountains that accumulate in oceans and rivers. However, large-scale commercial use of plastic-eating microorganisms is still years away, since their release in the environment could create additional unpredicted issues. Furthermore, the enzymes discovered and bioengineered have only been able to digest one type of plastic—PET. There are several major commercial types of plastic, such as polypropylene, which is used to make con-
Photo: Chokniti Khongchum
tainers, and high-density polyethylene, which is used in shampoo bottles and milk jugs. Additionally, the super enzyme doesn't degrade the plastic back to its core elemental building blocks (such as carbon and hydrogen), it breaks down the plastic into components that companies can reuse to create more plastic. Other concerns include the risk of releasing chemical additives stored in plastic products
and the potential unknown side-effects of releasing genetically engineered microorganisms into nature. Hence, the large-scale commercial use of plastic-eating enzymes is still years away. Apart from the bacteria found by scientists in Japan, several other organisms which can decompose plastic have been found. Scientists have reported a fungus that has been degrading plastic at a waste disposal Photo: Lucien Wanda
Photo: Stijn Dijkstra
site in Islamabad, Pakistan. In March 2020, German scientists discovered bacteria strains that could degrade polyurethane plastic while collecting soil from a brittle plastic waste site in Leipzig. Furthermore, tiny wax worms also have the ability to chomp through plastics such as polyethylene using the bacteria in their guts. Mealworms also possess this capability; around 3,0004,000 mealworms can break down a Styrofoam coffee
cup in about a week. Even with the recent discoveries of plastic-eating microorganisms, the fight against plastic pollution remains dependent on switching to reusable alternatives, ensuring that non-recyclable plastic waste ends up in a landfill rather than in the environment, and using biodegradable materials when possible.
