Researchers have genetically engineered a marine microorganism to break down plastic in saltwater
Specifically, the modified organism can break down polyethylene terephthalate (PET), a plastic used in everything from water bottles to clothing and a significant contributor to microplastic pollution in the oceans. Nathan Crook, author of a paper on the work and associate professor of chemical and biomolecular engineering at North Carolina State University, says, “This is exciting because we need to address plastic pollution in the marine environment.”
“One option is to remove the plastic from the water and dispose of it in a landfill, but that brings its own problems.” It would be better if we could break down these plastics into reusable products. For this to work, there needs to be a cost-effective way to break down plastic. Our work is a big step in this direction,” adds Crook.
To address this challenge, the researchers worked with two types of bacteria. The first, Vibrio natriegens, which grows in salt water and is characterized, among other things, by its rapid reproduction. The second bacteria is Ideonella sakaiensisis characterized by producing enzymes that allow it to break down and eat PET.
The researchers took DNA from I. sakaiensis responsible for producing the enzymes that break down plastic, and incorporated this genetic sequence into a plasmid. These are genetic sequences that can replicate in a cell independently of the cell’s own chromosome. In other words, you can introduce a plasmid into a foreign cell and it will carry out the instructions in the plasmid’s DNA. That’s exactly what the researchers did.
By introducing the plasmid that contained the genes of I. sakaiensis in the bacteria V. natriegens, the researchers got it to produce the desired enzymes on the surface of its cells. Then they showed that V. natriegens was able to decompose PET in a salt water environment at room temperature.
“From a scientific perspective, it’s exciting because it’s the first time this is possible.” V. natriegens “express foreign enzymes on the surface of their cells,” explains Crook. “From a practical perspective, it is also the first genetically modified organism we know of that is capable of degrading PET microplastics in saltwater,” adds Tianyu Li, lead author of the paper and a graduate student at NC State. “This is important because it is not economically viable to extract plastic from the ocean and rinse off the highly concentrated salts before starting any process related to plastic degradation.”
“While this is an important first step, there are still three significant obstacles,” says Crook. “First we want to include the DNA of I. sakaiensis directly to the genome V. natriegens, which would make the production of plastic-degrading enzymes a more stable feature of modified organisms. Second, we need to make more changes V. natriegens so that it can feed on the byproducts created when PET decomposes. Ultimately we have to change them V. natriegens to produce a desired end product from PET, for example a molecule that represents a useful raw material for the chemical industry.
“Honestly, the third challenge is the easiest of the three,” says Crook. “Decomposing the PET in the salt water was the most difficult part. We are also willing to talk to industry groups to find out which molecules would be best suited for the company. V. natriegens«Adds Crook. “Given the range of molecules we can encourage bacteria to produce and the potentially huge scale of production, what molecules could the industry provide a market for?”
REFERENCE
Degradation of polyethylene terephthalate microplastics under saltwater conditions using artificial Vibrio natrigens