Production and synthetic dyes decolourization capacity of a recombinant laccase from Pichia pastoris

Aims: To produce and purify a recombinant laccase from Pichia pastoris and to test its ability in decolourization of synthetic dyes. Methods and Results: A cDNA encoding for a laccase was isolated from Pycnoporus sanguineus and was expressed in P. pastoris strain SMD1168H under the control of the alcohol oxidase (AOX1) promoter. The laccase native signal peptide efficiently directed the secretion of the recombinant laccase in an active form. Factors influencing laccase expression, such as cultivation temperature, pH, copper concentration and methanol concentration, were investigated. The recombinant enzyme was purified to electrophoretic homogeneity, and was estimated to have a molecular mass of about 62 center dot 8 kDa. The purified enzyme showed a similar behaviour to the native laccase produced by P. sanguineus. Four different synthetic dyes including azo, anthraquinone, triphenylmethane and indigo dyes could be efficiently decolourized by the purified recombinant laccase without the addition of redox mediators. Conclusions: Heterologous production of P. sanguineus laccase in P. pastoris was successfully achieved. The purified recombinant laccase could efficiently decolourize synthetic dyes in the absence of mediators. Significance and Impact of the Study: This study is the first report on the synthetic dye decolourization by the recombinant P. sanguineus laccase. The decolourization capacity of this recombinant enzyme suggested that it could be a useful biocatalyst for the treatment of dye-containing effluents.