One-Pot Depolymerization of Mixed Plastics Using a Dual Enzyme System

As global plastic consumption and littering escalate, innovative approaches to sustainable waste management are crucial. Enzymatic depolymerization has emerged as a promising recycling method for polyesters via monomer recovery under mild conditions. However, current research mainly focuses on using a single plastic feedstock, which can only be derived from complex and costly plastic waste sorting. This study investigated the enzymatic depolymerization of mixed plastics using a dual-enzyme system in a one-pot approach. Employing the polyester hydrolase PES-H1 FY and the (poly)urethanase UMG-SP-2, mixed or blended polymers consisting of polyethylene terephthalate (PET), polybutylene adipate-co-terephthalate (PBAT), and thermoplastic polyester-polyurethane (TPU) were depolymerized into their monomers. A total yield of monomeric products of up to 39.8 ± 4.4% was determined by chromatographic quantifications after 96 h reactions, which was consistent with the weight loss measurements of 40.9 ± 2.5%. In addition, a modified dissolution-precipitation method was shown to easily blend the three different polymers while improving their degradability. Our findings suggest that using mixed enzymes is a viable method for recycling mixed or blended waste plastics without polymer sorting. Individual monomers can be separated to produce virgin polymers, while their mixture in the hydrolysate can easily serve as feedstock for microbial upcycling.