Current Advances in the Biodegradation and Bioconversion of Polyethylene Terephthalate

Abstract

Polyethylene terephthalate (PET) is a widely used plastic that is polymerized by terephthalic acid (TPA) and ethylene glycol (EG). In recent years, PET biodegradation and bioconversion have become important in solving environmental plastic pollution. More and more PET hydrolases have been discovered and modified, which mainly act on and degrade the ester bond of PET. The monomers, TPA and EG, can be further utilized by microorganisms, entering the tricarboxylic acid cycle (TCA cycle) or being converted into high value chemicals, and finally realizing the biodegradation and bioconversion of PET. Based on synthetic biology and metabolic engineering strategies, this review summarizes the current advances in the modified PET hydrolases, engineered microbial chassis in degrading PET, bioconversion pathways of PET monomers, and artificial microbial consortia in PET biodegradation and bioconversion. Artificial microbial consortium provides novel ideas for the biodegradation and bioconversion of PET or other complex polymers. It is helpful to realize the one-step bioconversion of PET into high value chemicals.

Recycling of polyethylene terephthalate wastes: A review of technologies, routes, and applications

“…The monomers produced from the hydrolysis of PET, TPA and EG, have been utilized by microorganisms, entering the tricarboxylic acid (TCA cycle) or being converted into high value chemicals. [ 95 ] In another study, TPA was produced from PET wastes and used together with the aluminum chloride hexahydrate to form metal organic framework. [ 96 ] Notably, an elementary‐level project of aluminum‐based metal organic framework has been recently prepared which exhibited high surface area, high porosity, and tuneable pore and has been widely used in different applications such as gas storage, molecular recognition, and drug delivery.…”

An Overview into Polyethylene Terephthalate (PET) Hydrolases and Efforts in Tailoring Enzymes for Improved Plastic Degradation

“…Then, the hydrolases bind to the PET films, and the degradation process begins. PET hydrolases hydrolyze the ester bonds of PET for transformation to terephthalic acid (TPA) and ethylene glycol (EG), which then yields mono-(2-hydroxyethyl) terephthalate (MHET) and bis(2-hydroxyethyl) terephthalate (BHET), as incomplete hydrolysis products [ 37 , 67 ].…”

“…Having said that, scientific research on PET should be geared toward sustainability by bioprospecting or developing more hydrolases that can cleave the ester linkages in the amorphous domain of PET to enable the bioremediation of PET [ 31 ], since various microorganisms naturally produce enzymes. Bio-based recycling can sustainably manage PET waste and degrade the produced monomers at the end of the process, yielding products with properties comparable to virgin PET that could be converted into high-value chemicals [ 37 ]. For example, Li et al [ 38 ] established a value-added recycling strategy by reusing PET waste as an anti-stripping agent in asphalt mixtures.…”

Valorization of Polyethylene Terephthalate to Muconic Acid by Engineering Pseudomonas Putida

“…PET can be depolymerized to monomers and oligomers by physical and chemical methods, such as pyrolysis, ammonolysis, hydrolysis, and glycolysis [ 4 ]. Many chemo-bioprocesses have been developed to synthesize high-value chemicals from the PET waste [ 5 ]. Using terephthalate (TPA) produced from PET pyrolysis as the feedstock, Kenny et al synthesized bioplastic polyhydroxyalkanoates (PHA) employing Pseudomonas strains isolated from PET-exposed soil [ 6 ], and Kim et al engineered Escherichia coli and Gluconobacter oxydans to synthesize higher-value products, such as gallic acid, pyrogallol, muconic acid (MA), vanillic acid, and glycolate [ 7 ].…”