Degradation of Tetracycline by Laccase–Mediator System Using Tea Polyphenols as Mediator

Abstract

Tetracycline antibiotics are widely used, but their resistance to degradation and persistence in the environment pose a potential risk of inducing antibiotic resistance, creating significant threats to both the environment and human health. This study established a laccase–mediator system (LMS) using natural green tea polyphenols (GTPs) as mediators for efficient tetracycline degradation. Through analyzing the main GTP components and optimizing the reaction conditions, the degradation efficiency of the system was evaluated. The experimental results indicated that, among the various tea polyphenol components, epicatechin gallate (ECG) contributed the most significantly to the degradation efficiency. Under optimized conditions, the Lac-ECG system degraded over 98% of tetracycline within 3–4 min. Further optimization of the Lac-GTP system allowed us to identify the following optimal conditions: a GTP concentration of 1.0 mmol/L, laccase concentration of 1.0 mg/mL, pH of 6.0, and temperature of 25 °C. Under these conditions, a degradation rate of 95.07% was attained within 5 min, outperforming a system using the synthetic mediator ABTS. Additionally, metal ions such as Ca2+, Mg2+, Cu2+, Fe3+, Fe2+, and Ni2+ were found to enhance the degradation process, while Mn2+ and Hg2+ exhibited inhibitory effects. Antibacterial activity tests revealed that the degradation products completely lost their antimicrobial activity, demonstrating effective detoxification of tetracycline. In conclusion, the tea polyphenol-based laccase–mediator system developed in this study exhibits high efficiency, cost-effectiveness, and environmental friendliness, offering a promising strategy for the remediation of tetracycline-contaminated environments.