Characterisation of free and immobilised laccases from <i>Ganoderma lucidum</i>: application on bisphenol a degradation
Tatiane Brugnari, Alex Graça Contato, Marita Gimenez Pereira, Emanuelle Neiverth de Freitas, Gisele Adriana Bubna, Guilherme Mauro Aranha, Adelar Bracht, Maria de Lourdes Teixeira de Moraes Polizeli, Rosane Marina Peralta
Abstract
Laccases (EC. 1.10.3.2) have a broad range of industrial applications. In order to overcome problems associated with loss of activity, storage and reusability of the free enzyme, a laccase from Ganoderma lucidum was immobilised successfully on monoaminoethyl-N-aminoethyl (MANAE)-agarose with high immobilisation yield and high activity recovery. The immobilisation improved significantly the thermal stability, with half-life 2.1- and 5.0-fold higher at 45 and 55 °C, respectively, in comparison with the free laccase. The storage stability at 4–8 °C of the immobilised laccase was also significantly higher than that the free form. Kinetic studies revealed that both free and immobilised G. lucidum laccases obeyed the Michaelis-Menten equation. Immobilisation increased Km and Vmax of the enzyme, reflecting a higher catalytic efficiency at high substrate concentrations. However, the Vmax/Km ratios were decreased by immobilisation, indicating a diminished catalytic efficiency at low substrate concentrations. The immobilised laccase was slightly more efficient than free laccase in the biodegradation of BPA. After 1 h, the immobilised laccase degraded 96.1 ± 3.0% of BPA at the initial concentration of 100 mg.L−1, whereas the free laccase removed 80.9 ± 3.5%. The immobilised G. lucidum laccase also efficiently degraded bisphenol A for at least 15 cycles of reuse.