Efficient immobilization of enzyme on covalent organo-framework for remediation of pyrene-contaminated soil and degradation mechanism.

Bioremediation of polycyclic aromatic hydrocarbons (PAHs) using immobilized enzymes has garnered significant interest due to its cost-effectiveness, stability, and efficiency. In this regard enzyme laccase have been extensively used for the remediation of organic contaminants in aqueous solutions. However, the use of a single and/or free enzyme may not show better results due to its rapid degradation and loss of activity. Moreover, the use of immobilized enzymes for remediating specific PAH compounds in soil remains underexplored. Therefore, the aim of the present study was to prepare laccase (Trametes versicolor) immobilized on a covalent framework for pyrene remediation in soil. Results showed that the immobilized enzyme retained 51.13 % of the relative activity throughout the course of 50 days of storage and outperformed the free enzyme in terms of relative activity at higher pH values (6 and 7), and temperatures (60 °C and 70 °C). The immobilized enzyme achieved a 92.38 % pyrene degradation rate in soil and enhanced soil phenol oxidase (S-PhOx), peroxidase (S-POD), and catalase (S-CAT) activities by 95.15 %, 50.03 %, and 54.77 %, respectively, on day 50 compared to the control. Furthermore, it boosted the soil bacterial population, including Gemmatimonas, Luteimonas, Lysobacter, Massilia, Longimicrobiaceae, Symbiobacterium, Ponibacter, Bacillus, and Sphingomonas. PCA analysis revealed a strong positive correlation between pyrene degradation percentage and S-CAT, S-POD, Gemmatimonas, Longimicrobiaceae, and Symbiobacterium. Thus, the immobilized enzyme offers a promising and sustainable approach for PAH removal from soil.