Genes for a Circular and Sustainable Bio-PET Economy

Abstract

Plastics have become an important environmental concern due to their durability and resistance to degradation. Out of all plastic materials, polyesters such as polyethylene terephthalate (PET) are amenable to biological degradation due to the action of microbial polyester hydrolases. The hydrolysis products obtained from PET can thereby be used for the synthesis of novel PET as well as becoming a potential carbon source for microorganisms. In addition, microorganisms and biomass can be used for the synthesis of the constituent monomers of PET from renewable sources. The combination of both biodegradation and biosynthesis would enable a completely circular bio-PET economy beyond the conventional recycling processes. Circular strategies like this could contribute to significantly decrease the environmental impact of our dependence on this polymer. Here we review the efforts made towards turning PET into a viable feedstock for microbial transformations. We highlight current bottlenecks in the degradation of the polymer and the metabolism of the monomers and we showcase fully biological or semisynthetic processes leading to the synthesis of PET from sustainable substrates.

Conformational Selection of a Tryptophan Side Chain Drives the Generalized Increase in Activity of PET Hydrolases Through a Ser/Ile Double Mutation

“…In this context, the discovery of PET hydrolases (PETases) 5,6 has emerged as a promising and environmentally friendly approach for plastic biorecycling. 7,8 These enzymes depolymerize PET into its main constituent monomers, which can then be used to resynthesize virgin PET and thus enable a fully circular plastic recycling process. 9 Most PETases are thermophilic, 5 with optimal activities near the glass transition temperature of PET (~65 ºC) where the polymer chains become more flexible and are prone to enzymatic hydrolysis, due to the inability of PETases to degrade highly crystalline PET.…”