A simple procedure for the isolation of laccase secreted by Pleurotus oestreatus

Abstract

Extracellular laccase was isolated from the residual substrate of Pleurotus oestreatus (oyster mushroom), without the addition of aromatic inducers, in order to investigate its potential as an effective tool for the biochemical transformation of lignified and polyphenol-containing crop residues. The crude enzyme was purified by subjecting samples to ammonium sulphate precipitation, gel filtration chromatography using Sephadex G-75, and anion exchange chromatography on DEAE-cellulose. The laccase was purified to electrophoretic homogeneity and it exhibited chemical characteristics similar to those of laccases in other studies. The purified laccase was estimated to have a molecular mass of 78 kDa. The laccase oxidized dimethoxyphenol optimally at pH 5.0 and significantly over a wide pH range (4.5 to 8) and showed maximum laccase activity at 50oC. These findings provide an important opportunity for the isolation of laccase from the residual substrate of Pleurotus ostreatus on a commercial scale. More importantly, treatment of crop residues with laccase will make available feed ingredients that contain minimal levels of lignin and polyphenols.