Sloane Mandelbaum (VI), Sofia Wood (VI), Sari Berman (V), Edward Huang (V), Julia Ronnen (V), Jasmine Zhou (IV), Noah Reichman (IV)
Project Summary
The United States of America only recycles about 32% of its total waste, sending nearly 150 million tons of trash to landfills each year. There, it takes up to 450 years to fully biodegrade. Often, it ends up invading oceans or forests, where it poses a serious threat to native species. Polyethylene terephthalate (PET) is one of the most widely used plastics globally, but only 9% of the 56 million tons of PET produced annually is recycled. It is necessary to find an efficient way to recycle plastic in order to mitigate the damage done to our planet.
Our team works with PET depolymerase (PETase), an enzyme with the unique ability to break PET polymers into monomers, which can then be reassembled into new plastic. This nuanced recycling method is termed “biochemical recycling” and has become an increasing focus of research—however, it requires optimization before it can be implemented commercially. Because the severity and pervasiveness of plastic-related damage to the environment is growing, the scientific community is eagerly seeking to improve PETase through mutation–specifically, its efficiency and thermostability.
Project Goals
Our goal is to identify and investigate various mutations, and assess the change in efficiency and thermostability that each mutation offers. To determine the efficacy of mutant PETase, we plan to use a PCL-clearing assay. This assay would allow our enzyme to degrade PCL (more commercially available than PET) through a clearing halo that we can measure. A larger clearing halo would prove greater efficiency. This experiment will allow tangible results of whether, and how efficiently, our PETase mutants are capable of degrading PET/PCL plastic. By comparing the rate of degradation to our Wildtype PETase, we will find out which mutant is the most efficient.
We are currently performing this assay with a PETase mutant containing a signal peptide, which allows our enzyme to exit the cell in order to break down the plastic. If successful, we can clone signal peptides onto our other mutants in order to test them as well.
In the coming months, we hope to make more progress researching and documenting the effects of mutation on PETase activity, which will further our understanding of the enzyme, and contribute to the global effort to make recycling more efficient and widely used.
Faculty Advisor
Dr. D'Ausilio
PETase has PETential! Bon APETit!
Works Cited:
Almeida EL, Carrillo Rincón AF, Jackson SA and Dobson ADW (2019) In silico Screening and Heterologous Expression of a Polyethylene Terephthalate Hydrolase (PETase)-Like Enzyme (SM14est) With Polycaprolactone (PCL)-Degrading Activity, From the Marine Sponge-Derived Strain Streptomyces sp. SM14. Front. Microbiol. 10:2187. doi: 10.3389/fmicb.2019.02187.
Tournier, V., Topham, C.M., Gilles, A. et al. An engineered PET depolymerase to break down and recycle plastic bottles. Nature 580, 216–219 (2020). https://www.nature.com/articles/s41586-020-2149-4
