Characterisation of free and immobilised laccases fromGanoderma lucidum: application on bisphenol a degradation

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 fromGanoderma lucidumwas 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 degrees C, respectively, in comparison with the free laccase. The storage stability at 4-8 degrees C of the immobilised laccase was also significantly higher than that the free form. Kinetic studies revealed that both free and immobilisedG. lucidumlaccases obeyed the Michaelis-Menten equation. Immobilisation increasedK(m)andV(max)of the enzyme, reflecting a higher catalytic efficiency at high substrate concentrations. However, theV(max)/K(m)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 immobilisedG. lucidumlaccase also efficiently degraded bisphenol A for at least 15 cycles of reuse.

Automated summary

The laccase from Ganoderma lucidum was successfully immobilised on MANAE-agarose, improving thermal stability and storage stability. Immobilization increased the catalytic efficiency at high substrate concentrations but decreased at low substrate concentrations. The immobilised laccase showed higher efficiency in degrading BPA and remained efficient for at least 15 cycles of reuse.