An efficient decolorization of methyl orange dye by laccase from Marasmiellus palmivorus immobilized on chitosan-coated magnetic particles

The oxidation activity of laccase on a broad range of substrates has attracted great interest in the development of technologies for industrial and environmental applications. In this work, a crude laccase from Marasmiellus palmivorus was immobilized onto chitosan-coated magnetic particles. The support was developed and characterized by X-ray diffraction, vibrating sample magnetometer (VSM), specific surface area, and pore size by BET/BJH method, and Fourier Transform Infrared Spectroscopy (FTIR). Magnetic particles retained approximately 30% of magnetization (19.5 emu/g) after enzyme immobilization. The highest activity of the immobilized crude laccase was 139.84 U.g dry support(-1) (48.74% efficiency and 99% yield) when 25 mg protein. g dry support(-1) were applied in the support previously activated with 90 mM glutaraldehyde. Enzyme immobilization was fast, reaching maximum recovered activity (36%) after 5 min of contact with the support. The optimum pH of the soluble and immobilized crude laccase was 5.5 and the optimum temperature varied between 40 and 50 degrees C for the soluble form and between 25 and 35 degrees C for the immobilized form. Immobilization increased the thermal stability of the enzyme by a factor of 1.33. Decolorization reaction of methyl orange dye using ABTS (2,2-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt) as a mediator allowed 30 cycles of reuse with a percentage of decolorization above 60%.