Complete enzymatic depolymerization of polyethylene terephthalate (PET) plastic using a Saccharomyces cerevisiae-based whole-cell biocatalyst

Plastics like polyethylene terephthalate (PET) have become an integral part of everyday life, yet plastic waste management remains a significant challenge. Enzymatic biocatalysis is an eco- friendly approach for recycling and upcycling of plastic waste. PET-hydrolyzing enzymes (PHEs) such as IsPETase, along with its engineered variants like FAST-PETase, demonstrate promising PET depolymerization capabilities at ambient temperatures. Whole-cell biocatalysts, displaying PHEs on their cell surface, offer high efficiency, reusability, and stability for PET depolymerization. However, their efficacy in fully breaking down PET is hindered by the necessity of two enzymes - PETase and MHETase. Current whole-cell systems either display only one PHE or struggle with performance when displaying larger passenger proteins like the MHETase-PETase chimera. In this work, we developed a Saccharomyces cerevisiae-based whole-cell biocatalyst system for complete PET depolymerization. Leveraging a cellulosome-inspired trifunctional protein scaffoldin displayed on the yeast surface, we immobilized FAST-PETase and MHETase, forming a multi-enzyme cluster. Our whole cell biocatalyst achieved complete PET depolymerization at 30{degrees}C, yielding 4.9 mM TPA in seven days with no intermediate accumulation. Furthermore, we showed improved PET depolymerization ability by binding FAST-PETase at multiple sites on the trifunctional scaffoldin. This breakthrough in complete PET depolymerization marks an essential step towards a circular plastic economy.