In a breakthrough study, researchers at NC State have genetically engineered a marine microorganism to break down plastics in salt water, specifically targeting PET (polyethylene terephthalate).
PET is a significant contributor to the growing issue of microplastic pollution in our oceans and is widely used in everyday products ranging from water bottles to clothing.
“Like other plastics, PET resists natural degradation, thus accumulating in the environment. Several recycling strategies have been applied to PET, but these tend to result in downcycled products that eventually end up in landfills,” wrote the study authors.
“This accumulation of landfilled PET waste contributes to the formation of microplastics, which pose a serious threat to marine life and ecosystems, and potentially to human health.”
The research was focused on two specific bacteria species: Vibrio natriegens, which thrives in saltwater, and Ideonella sakaiensis, which produces enzymes that break down and metabolize PET.
The DNA from Ideonella sakaiensis was extracted and embedded into a plasmid, a form of genetic sequence that has the capability to replicate within a cell independently, without reliance on the cell’s inherent chromosome.
This plasmid, now carrying the genes from I. sakaiensis, was introduced into the V. natriegens bacteria.
As a result, V. natriegens began to produce the enzymes required to break down PET on the surfaces of their cells. The team demonstrated that V. natriegens could actively break down PET in saltwater conditions at ambient room temperatures.
“In this work, we present a collection of engineered Vn strains that can depolymerize PET particles under ambient conditions and in media containing high concentrations of salts,” wrote the researchers.
Study co-author Nathan Crook, a chemical and biomolecular engineer at North Carolina State University, highlighted the significance of the research.
“This is the first time anyone has reported successfully getting V. natriegens to express foreign enzymes on the surface of its cells,” said Crook.
“From a practical standpoint, this is also the first genetically engineered organism that we know of that is capable of breaking down PET microplastics in saltwater,” noted study lead author Tianyu Li.
While the researchers acknowledge that other challenges still need to be addressed, Crook said that breaking down the PET in saltwater was the most challenging part of their work.
“Microplastic detection, recovery, and remediation are highly complex problems requiring solutions at the intersection of multiple disciplines,” wrote the study authors.
“This work establishes Vn as a promising chassis for expression and display of plastic-degradation enzymes, allowing it to be easily compatible with marine plastic recovery efforts.”
The research is published in the AIChE Journal, and was funded by the National Science Foundation.
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