Degradation mechanism of PGNa by the immobilized degrading enzymes from magnetic fermentation residue biochar

The development of a method to efficiently remove high concentrations of penicillin G sodium (PGNa) from the environment is important for human and animal health and safety. In this study, the degradative enzymes were immobilized by adsorption using biochar from penicillin fermentation waste residue, which could efficiently remove PGNa (900 mg/L) from an aqueous solution, with a removal rate of 99.84 % within 20 min. The successful immobilization of the PGNa-degrading enzymes was verified by scanning electron microscopy, Fourier transform infrared spectroscopy and thermogravimetric analyzer. The adsorption mechanism of SAMB on the enzymes was also analyzed by adsorption kinetics and molecular docking calculations, which were mainly chemisorption and physisorption. By comparing with the free enzymes, the immobilized enzymes were found to have better thermal stability, pH adaptability, reusability, and storage stability. In addition, combined with the LC-MS analysis of the removal products, three removal pathways were postulated, including the reactions of β-lactam ring cleavage, decarboxylation, demethylation, deamidation, and oxidation. Finally, the toxicity of the removal products was evaluated using ECOSAR software, and the results showed that the intermediate products had low toxicity. This study is the first to use penicillin waste residue immobilized degradative enzymes to remove PGNa, and it provides a new low-cost option for remediation of PGNa contamination in the environment. It is important for the efficient degradation of residual PGNa in the environment.