H₂O₂-driven enzymatic degradation of halophenols and toxicity assessment

Abstract

Halophenols (HPs) cause serious problems for the health of living beings and environment due to their toxigenicity, mutagenicity and carcinogenicity. Enzymes have recently attracted significant attention as an eco-friendly and sustainable approach for the environmental remediation of pollutants. In this study, the recombinant unspecific peroxygenase from Agrocybe aegerita (r Aae UPO, recombinantly expressed in Komagataella pastoris known as Pichia pastoris ) was used to degrade five representative HPs (2-Chlorophenol (2-CP), 3-Chlorophenol (3-CP), 4-Chlorophenol (4-CP), 4-Bromophenol (4-BP), and 3-Iodophenol (3-IP)) in the batch and fed-batch systems. r Aae UPO (5 µM) completely removed up to 10 mM HPs from the fed-batch system in 48 h, while the almost complete removal of 2.5 mM 4-CP and 4-BP in batch systems occurred within 72 h. The enzyme was more effective upon slow, continuous fed with H₂O₂ concentrations (2 mM/h) than supplying stoichiometric H₂O₂ from the beginning. The activity of r Aae UPO towards HPs was: 3-IP > 2-CP > 3-CP > 4-BP > 4-CP. These results were also confirmed by molecular docking results. r Aae UPO-catalyzed primary degradation of HPs occurred via catechol formation followed by polymerization. Toxicity assays using E. coli DH5α demonstrated a significant reduction in toxicity after enzymatic degradation of HPs. This study revealed that r Aae UPO is an efficient biocatalyst capable of effectively degrading HPs, showing great potential for environmental bioremediation applications.