Purification and characterization of laccase from <i>Trametes hirsuta</i> Bm-2 and its contribution to dye and effluent decolorization

Abstract

In this study, the results demonstrated that Trametes hirsuta Bm-2 produced inducible laccases from wheat bran. Two laccase isozymes were partially purified by ammonium sulfate precipitation, anion-exchange chromatography and size-exclusion chromatography. The major laccase LacI, is a monomeric protein with apparent molecular mass of 65 kDa (SDS-PAGE). The optimal pH of the enzyme is 4 to 4.5 and the optimal temperature is 40 to 60°C with good stability up to 65°C. The Km values for non phenolic substrate 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) and phenolic substrate 2,6-dimethoxyphenol (DMP) are 68 and 164 μM, respectively. Activity is increased by the addition of 1 mM Mn²⁺, which is resistant to Ca²⁺, Cu²⁺ and Cd²⁺ ions, partially resistant to EDTA and strongly inhibited by sodium azide, SDS and cysteine. Also, LacI is very resistant to ethanol and acetonitrile (20%), retaining 100% activity after 24 h incubation. Laccase was able to decolorize 100% dye acid blue and 36% textile effluent without any mediator addition, suggesting that it has the potential of been applied in bioremediation and synthesis of organic processes.

Key words: Trametes hirsuta, purification, laccases, effluent decoloration.