Interfacial microenvironment engineering of functionalized MOFs for immobilizing PET hydrolase ICCG to overcome the activity-stability trade-off in efficient PET depolymerization.

Abstract

The leaf-branch compost cutinase variant (ICCG) is a promising enzyme for the depolymerization of polyethylene terephthalate (PET). However, its industrial application is hindered by poor operational stability and difficulty in reutilization. Immobilization on MOFs can overcome these limitations, but often suffers from an activity-stability trade-off. In this work, a series of zirconium-based MOFs functionalized with different groups were employed as platforms for ICCG immobilization to strengthen and optimize enzyme-MOF interactions, thereby constructing a favorable interfacial microenvironment for ICCG and breaking the activity-stability trade-off. ICCG was immobilized via physical adsorption, and systematic evaluation revealed that the amine-functionalized carrier yielded the optimal biocomposite (ICCG@ZrBTB-NH2). Compared with its free counterpart, the immobilized enzyme exhibited significantly enhanced stability under harsh operational conditions (elevated temperature, varied pH, and chemical agents) and superior reusability. Crucially, ICCG@ZrBTB-NH2 produced approximately twice the amount of terephthalic acid (TPA) as free ICCG during PET hydrolysis. Molecular docking and dynamics simulations provided mechanistic insights, revealing that the functional groups on the MOF strengthen enzyme-support interactions and help maintain the enzyme's active conformation. This study not only presents a highly efficient and robust biocatalytic system for PET degradation but also establishes a rational design principle-microenvironment engineering via MOF functionalization-for developing advanced immobilized enzymes for plastic waste valorization and beyond.