Partial purification and immobilization of laccase isolated from medicinal mushroom (Ganoderma lucidum)

Abstract

Ganoderma lucidum, a white rot fungus is used as a source for laccase isolation. The production of laccase has been carried out using by submerged fermentation and the crude enzyme obtained showed activity of 0.42 µg/mL/min. Laccase is partially purified using ammonium sulphate precipitation which showed activity of 0.71 µg/mL/min and it was further purified by DEAE cellulose chromatography with an activity of 0.95 µg/mL/min. Partially purified laccase is immobilized by covalent attachment onto a polyvinyl alcohol (PVA) membrane with retention of 65.71% of initial activity of the enzyme. After immobilization the optimum pH of the enzyme increases from 4.5 to 5.0 and temperature for maximum activity increases from 45ºC to 55ºC. The immobilized enzyme show its maximum activity at 10 mM of guaiacol concentration which is more than that of free enzyme (8 mM). Compared with the free enzyme, the immobilized enzymes display a higher activity and affinity, also improved thermal and operational stabilities. Finally, covalently immobilized laccase on PVA has been found to exhibit significant advantages such as reusability, economic benefits, and the cheap support, all these interesting properties, show the suitability of these biocatalysts for industrial applications.