Engineering enzymes to degrade microplastics in wastewater

Project Overview

Engineering enzymes to degrade microplastics in wastewater

Each year much of the 300 million tons of discarded plastic ends up as toxic microplastics in our wastewater. Wastewater treatment facilities have been targeted as a potential intervention point for microplastic biodegradation by enzymes. This project has successfully engineered new enzymes that are capable of breaking down some microplastics in the difficult conditions found in sewage sludge. 

Each year 300 million tons of plastic are discarded, contributing to an environmental accumulation of over 5 billion tons of plastic waste, much of which is in the form of toxic microplastics. Wastewater treatment facilities are a known route of microplastic introduction into the environment, so these facilities have been targeted as a potential intervention point for microplastic biodegradation by enzymes. However, most enzymes identified or engineered to date have not been designed for performance in wastewater treatment conditions. 

A novel PETase enzyme that can break down plastics was discovered in Japan in 2016. The enzyme, which originated in the Ideonella sakaiensis bacteria, targets polyethylene terephthalate (PET), which is one of the most abundant plastics in the world. Since then, scientists have been working to discover and engineer similar enzymes that can biodegrade PET more quickly and sustainably than traditional recycling methods. For this project, our goal was to leverage protein engineering to enhance enzyme performance under complex, often extreme environments. In this case, the goal was to engineer a PETase that could digest microplastics during waste water treatment to mitigate the spread of microplastics to the environment. 

The Impacts

We have engineered new PETase enzyme variants designed to perform in the complex conditions typical of sewage sludge. These enzymes break down microplastics into small products that can be used as an energy source for bacteria in the wastewater treatment process. We have also engineered a PETase mutant capable of self-assembly onto sand supports – sand-based filters are quite common in wastewater treatment plants, so this ability should enable wastewater treatment operators to recover and re-use these enzymes more frequently before the enzymes themselves break down. In our project, we guided our PETase mutants to improve catalytic efficiency. By so doing, we gained valuable insights into how the molecular engineering of PETase can optimize applications across a wide range of uses. 

Advances in enzyme engineering technologies have broad impact to the public beyond the goals of this project. We seek to benefit the general public directly by developing and improving technologies which can reduce microplastics in the environment. 

Julie Goddard assistant professor.

Principal Investigator

Project Details

  • Funding Source: Hatch
  • Statment Date: 2023
  • Status: Completed project
  • Topics: Water, microplastics, pollution, sustainability