Robust cellular transformations of PET deconstruction products by import of glycol esters.

Abstract

Efforts to transform polyethylene terephthalate (PET) deconstruction products using live cells have been limited by terephthalic acid (TPA) uptake. Here, we used an intracellular carboxylate reduction assay to show that apparent TPA uptake in <i>E. coli</i> cells that lack a dedicated TPA transporter sharply increases from pH 6 to 5. More importantly, we found that glycol ester deconstruction products, mono(2-hydroxyethyl) terephthalate (MHET) and bis(2-hydroxyethyl) terephthalate (BHET), unexpectedly each result in rapid pH-independent uptake. We exploited glycol ester uptake, along with deletion of 22 cellular oxidoreductases, to design intracellular hydrolysis routes for synthesis of upcycled reduction products from BHET at >90% yields and from real PET wastes after tandem catalytic glycolysis and cell-based valorization at >80% combined yields. Our work has important ramifications for PET utilization by cells and adds new perspectives on the evolution of the PETase/MHETase system.