Laccase-Assisted Degradation of Anticancer Drug Etoposide: By-Products and Cytotoxicity

Emerging pollutants are compounds arising from human development, such as personal care products and pharmaceutical drugs, that reach rivers, lakes, and groundwater through wastewaters and have a potential risk to human health and the environment, which are not yet addressed in any laws. Anticancer drugs are a class of pharmaceutical drugs that exhibit recalcitrant behavior to conventional wastewater treatments. They have been found in domestic, industrial, and hospital wastewater, and some studies proved they can be mutagenic, genotoxic, and teratogenic to humans and wildlife. On this subject, the present study describes the enzymatic degradation of etoposide by several laccase activities and pHs. Moreover, the kinetic studies were performed in etoposide concentrations ranging from 500 to 18,000 µg·L−1. The degradation products were investigated by high-performance liquid chromatography/mass spectrometry (LC–MS/MS), and the toxicity was evaluated against L-929 cell line. The results showed that the laccase activity of 1100 U·L−1 completely degraded etoposide in 60 min, and even the laccase activity of 55 U·L−1 could remove 86% of the etoposide after 360 min. Laccase also degraded etoposide in all evaluated pHs, even in conditions similar to wastewater treatment plants (pH 6 and 7). The biocatalysis followed a first-order kinetics behavior and the degradation kinetics constant was k = 0.0477 min−1. The mass spectroscopy suggested that the degradation mechanism of etoposide was by dehydration and demethylation. Furthermore, laccase degraded etoposide to a non-toxic bio-product in which all tested concentrations show no reduction in metabolic activity of the tested cell line. The results of the etoposide degradation strongly suggested that laccase shows the potential to remove anticancer drugs in wastewater treatment plants.