A promising laccase immobilization using electrospun materials for biocatalytic degradation of tetracycline: Effect of process conditions and catalytic pathways

Abstract

• Novel poly(methyl methacrylate)/Fe 3 O 4 electrospun material was obtained. • The laccase immobilization by covalent binding and encapsulation was carried out. • The biocatalysts are characterized by improvement stability and reusability. • Removal of tetracycline by immobilized enzyme at wide range of pH and temperature. • Oxidation, dehydrogenation and demethylation governed conversion of tetracycline. In the presented study poly(methyl methacrylate) (PMMA) and magnetite nanoparticles were used to prepare novel PMMA/Fe 3 O 4 electrospun nanofibers. The obtained materials were characterized, and then modified and used as supports for covalent binding and encapsulation of laccase from Trametes versicolor . High enzyme loading (63.2 mg of laccase per 1 cm 2 of support) was recorded for the system after covalent binding, and the formation of stable interactions was confirmed, as leaching of the enzyme from the support did not exceed 12%. Furthermore, the obtained biocatalytic systems exhibited excellent pH, thermal and storage stability as well as reusability: after 40 days of storage and 5 successive biocatalytic cycles they retained 80% of their initial properties. Experiments on the removal of antibiotic showed that both immobilized laccases possess high ability to convert tetracycline. Under optimal process conditions (pH 5, temperature 25 °C, tetracycline solution concentration 1.0 mg L −1 ) the removal efficiency reached 100% and 94% for covalently bonded and encapsulated laccase. Finally, the degradation products were examined to investigate the degradation mechanism. The data showed that oxidation, dehydrogenation and demethylation are major reactions in the degradation of tetracycline using immobilized laccase. The findings demonstrate clearly that laccase immobilized by covalent binding and encapsulation using electrospun materials has the potential for application in environmental protection processes for the removal of antibiotics.