Synergistic Degradation of Parabens via Laccase/TEMPO/Cutinase System: Performance and Mechanism

To develop a green enzymatic method for the remediation of parabens (PBs) contaminants, a ternary composite system comprising laccase, 2, 2, 6, 6-tetramethylpiperidine-1-oxyl (TEMPO) mediator, and cutinase SE50 (LCTM) was constructed. Using methylparaben (MP) as a model substrate, the degradation performance, kinetic characteristics, and underlying mechanisms of the system were systematically investigated. The results demonstrated that TEMPO significantly enhanced the catalytic conversion of MP by laccase, and the subsequent introduction of cutinase SE50 further boosted the overall degradation efficiency. Under the optimized conditions (0.5 U/mL cutinase SE50, 1.2 U/mL laccase, 25 mg/L TEMPO, temperature 50 °C, and pH 6.0), the degradation rate of MP reached 96.8% within 24 h. The degradation process well conformed to a pseudo-first-order kinetic model with an apparent reaction rate constant of 191.84 × 10⁻³ h⁻¹. Subsequently, identification of the degradation products revealed that MP was initially hydrolyzed into p-hydroxybenzoic acid, and then underwent decarboxylation and pivotal hydroxylation to generate the core intermediate catechol. Catechol then underwent oxidative ring-cleavage into small-molecule organic acids, including succinic, pyruvic, and glycolic acids, which were ultimately mineralized. Furthermore, the effects of different PBs structures on degradation efficiency were investigated, with higher degradation efficiency observed for short-chain substrates possessing lower steric hindrance. This study validates the potential application of the LCTM system in the remediation of ester-based pollutants and provides a theoretical basis for composite enzymatic degradation mechanisms.