Laccase from Trametes versicolor was immobilized by covalent bonds formation on CPC silica carriers. Elimination of two floroqinolone (FQ); enrofloxacine (ENR) and flumequine (FLU) using laccase in both free and immobilized form in the absence and presence of 1-hydroxybenzotriazole (HBT) and 4-Hydroxybenzoic acid (HBA) as mediators was investigated. Temperature, pH and storage stability of immobilized laccase was significantly improved compare to free laccase. In the absence of a laccase mediator, the initial concentrations of 50 mg L–1 of ENR and FLU decreased by 19 % and 28 %, respectively, after 6 h treatment using the immobilized laccase, while, the removal percentages were increased to 98 % and 96 %, respectively, when the immobilized laccase was used in presence of HBT. Whereas, the removal percentages of ENR and FLU were increased to 97 % and 88 %, respectively, when the immobilized laccase was used in presence of HBA. After twenty runs of the enzymatic elimination (laccase-HBT system) of ENR and FLU, the immobilized laccase exhibited the relative removal of 17.63 % and 15.62 %, respectively. The results of microtoxicity test (growth inhabitation percentage of six bacterial strains) showed a significant decrease in toxicity of the laccase-treated ENR and FLU solution.
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