Application of Mhetase-Displaying Whole-Cell Biocatalysts for Conversion of PET-Degradation Intermediates

Enzymatic depolymerization is a promising solution to manage polyethylene terephthalate (PET) waste.¹ Complete PET enzymatic degradation to terephthalic acid (TPA) and ethylene glycol (EG) needs the synergistic action of two enzymes, PETase and MHETase.² MHETase facilitates conversion of MHET, an intermediate in the PETase-based enzymatic degradation process, to TPA, and prevents inhibition of PETase activity. Surface display of PET-degrading enzymes is an attractive approach to achieve improved activity and eliminate the need of protein purification, but current work has focused on the surface display of only one PET-degrading enzyme.³ Thus, complete PET depolymerization has not been achieved. Our hypothesis is that an engineered bacterial community can be developed for complete PET depolymerization, with one part of the community displaying MHETase.

In this work, whole cell biocatalysts displaying PET-degrading enzyme MHETase on the surface of Escherichia coli (E. coli) was constructed. MHETase was surface displayed on E. coli using transporter proteins YeeJ³ and AIDA-I⁴ because of their demonstrated ability to efficiently surface display heterologous passenger proteins. After expression, activity of surface displayed MHETase was determined by incubating cells with dissolved MHET to confirm the activity of both AIDA-I-MHETase and YeeJ-MHETase via HPLC analysis. This work is an essential step in achieving complete PET depolymerization to its constituent monomers which can be upcycled, potentially by other members of the bacterial community or through other methods.