Clean Enzymatic depolymerization of highly crystalline polyethylene terephthalate in moist-solid reaction mixtures

Less than 9% of the plastic produced is recycled after use, contributing to the global plastic pollution problem. While polyethylene terephthalate (PET) is one of the most common plastics, its thermomechanical recycling generates a material of lesser quality. Enzymes are highly selective, renewable catalysts active at mild temperatures; however, the current consensus is that they lack activity towards the more crystalline forms of PET. We report here that when used in moist-solid reaction mixtures instead of the typical dilute aqueous solutions, enzymes can directly depolymerize high crystallinity PET in 13-fold higher space-time yield and a 15-fold higher enzyme efficiency than prior reports. Further, this process shows a 26-fold selectivity for terephthalic acid over other hydrolysis products, which allows the direct synthesis of UiO-66 metal-organic framework.