A novel thermostable PETase from Kibdelosporangium aridum: Heterologous expression, immobilization and poly(ethelene terephthalate) decomposition applications

Abstract

Polyethylene terephthalate (PET) is a widely used plastic in various industries, contributing significantly to environmental pollution. Conventional methods for PET degradation are often associated with high costs, limited efficiency, and environmental harm. Consequently, biological approaches are gaining interest as sustainable, cost-effective, and environmentally friendly alternatives for PET degradation. This study focused on the expression, biochemical characterization, and immobilization of a novel PETdegrading cutinase, known as PETase, isolated from Kibdelosporangium aridum (KaPETase). This enzyme presents a new thermostable alternative for addressing PET biodegradation at elevated temperatures. The cutinase gene from Kibdelosporangium aridum was transformed into Escherichia coli BL21 (DE3) cells using the pET-22b(+) plasmid. The resulting recombinant KaPETase was purified by Ni-NTA chromatography, yielding a specific activity of about 6 U mg-1. The enzyme was immobilized in ZIF-8 and crosslinked with glutaraldehyde. The optimal pH and temperature for KaPETase preparations were determined to be 8.0 and 75 degrees C, respectively. In addition, the free enzyme maintained 80 % of its maximum activity at 100 degrees C. Through immobilization in ZIF-8, the catalytic efficiency and thermal stability of KaPETase were enhanced approximately three- and four-fold, respectively, PET degradation was analyzed using scanning electron microscopy and Fourier-transform infrared spectroscopy, demonstrating the strong potential of both free and immobilized KaPETases for effective PET decomposition. Future research could focus on advanced in silico analyses, enzyme engineering, bioprocess scaling, and comprehensive assessments of PET degradation to further optimize this approach.