Laccase-evoked removal of antibiotics: Reaction kinetics, conversion mechanisms, and ecotoxicity assessment

Antibiotics in ecosystems stimulate the emergence and development of antibiotic-resistant bacteria and genes, consequently posing tremendous health risks to wildlife species and humans. Laccase, a multicopper-containing oxidoreductase, is capable of nonspecifically catalyzing oxidization of multiple hazardous micropollutants, including antibiotics, with O2 as the terminal electron acceptor. Thus, laccase is recognized as a promising "green and sustainable biocatalyst" for the decontamination of antibiotics. Recently, great efforts have been made to design and exploit immobilized laccase to tackle antibiotics in the environment. In this review, the occurrence, fate, and ecological risks of antibiotics in environmental matrices are described. Moreover, the immobilized laccase-evoked removal of antibiotics, owing to immobilization technology reinforcing the stability and reusability of free laccase in bioremediation, is examined in details. In particular, advances in laccase-provoked transformation mechanisms (i.e. oxidative decomposition and radical polymerization) of antibiotics are highlighted, and a valuable guideline beneficial to large-scale practical applications is provided. Furthermore, evaluation of the intermediate products of antibiotics and their ecotoxicity in different laccase-enabled treatments is summarized. Finally, new directions for the application of laccase for effective antibiotic removal are envisaged, and several future directions to address the challenges are proposed.