Upcycling of Polyethylene Terephthalate Using Petase and Deep Eutectic Solvents

Plastics are becoming a major waste product across the world. Plastic upcycling involves depolymerizing plastic into its monomers for reuse and it has the potential to create a new avenue in plastic recycling and new market for value-added products.

Polyethylene terephthalate or PET is a thermoplastic polyester that is relatively chemically inert and resistant to microbial degradation. Currently, the most common method of depolymerizing PET is with expensive, environmentally harmful chemicals. However, there has been a recent discovery of a microbe that has evolved in a high PET environment and is able to degrade and metabolize PET through the use of its PETase enzyme. Deep eutectic solvent (DES) is a class of ionic solvent that incorporates one or more compounds to form eutectic mixture with a melting point lower than either of the original compounds often resulting in a liquid at room temperature. DES has low volatility and potentially better thermostability and biocompatibility, and has been shown to be able to solubilize PET. Using DES as a solvent in a PETase and PET reaction has the potential to become a cheaper alternative to the current PET upcycling methods. This study explored the biocompatibility of different DESs and PETase as well as which compatible DES has the highest rate of solubility of PET. Results from this work lead to a better understanding of the interactions between PETase and DES and help to the development of a biocatalytic plastic upcycling method using DES.