Heterologous expression and characterization of three laccases obtained from Pleurotus ostreatus HAUCC 162 for removal of environmental pollutants

Abstract

Chlorophenols (CPs), nitrophenols (NPs), and sulfonamide antibiotics (SAs) are three types of environmental pollutants that are of great concern because of their prevalence and toxicity. In this study, three laccase isoenzymes obtained from Pleurotus ostreatus HAUCC 162 were heterologously expressed and characterized with respect to their ability to degrade CPs, NPs, and, SAs. The three recombinant laccases can efficiently degrade the three types of considered pollutants using a laccase-mediator system (LMS). Their specific efficiencies for the removal of 2NP, 3NP, 4NP, 4CP, 2,4-dichlorophenol (DCP), 2,6-DCP, sulfadiazine (SDZ), sulfamethazine (SMZ), and sulfamethoxazole (SMX) over 60min were 59.21%, 47.91%, 60.24%, 74.9%, 28.9%, 35.1%, 98.1%, 97.5%, and 97.8%, respectively. Based on the analysis of the oxidation products of the CPs, NPs, and SAs, pollutant removal pathways are proposed, namely, the production of 3-nitromuconate and 3-chloromuconate as the key intermediates of 4-NP and 2, 4-DCP; and oxidative coupling for the transformation of SDZ by LMS. The results of present work indicated the laccases could efficiently remove NPs, CPs, and SAs in LMS, which offers an opportunity to apply P. ostreatus HAUCC 162 laccase in the field of environmental biotechnology.