Purification, characterization, and cloning of an extracellular laccase with potent dye decolorizing ability from white rot fungus Cerrena unicolor GSM-01

Abstract

A novel laccase was purified from fermentation broth of the white rot fungus Cerrena unicolor strain GSM-01 following three ion-exchange chromatography steps and one gel-filtration step. The purified enzyme was determined to be a monomeric protein of 63.2kDa and demonstrated high oxidation activity of 2.05×10⁴U/mg towards ABTS. Its cDNA, gene, and amino acid sequences were obtained. It possessed high sequence similarity with that of other laccases but different enzymatic properties. It manifested optimal pH and temperature of 2.6 and 45°C, respectively. Fe³⁺ and Fe²⁺ were the most efficient inhibitors towards Cerrena unicolor laccase (CUL), while Mn²⁺ can slightly enhance the laccase activity of 3.8-10.5%. The K_m and V_max of CUL were estimated to 302.7μM and 13.6μMm^-1, respectively. CUL was effective in the decolorization of bromothymol blue, evans blue, methyl orange, and malachite green with decolorization efficiencies of 50%-85%. It possesses potential application in textile and environmental industries.

Keywords: Cerrena unicolor; Laccase; Purification and cloning.