Novel biocatalyst from Microthielavia ovispora VKM F-1735 for industrial dye decolorization in the absence of mediators

Abstract

The new ascomycete Microthielavia ovispora VKM F-1735 has been found to produce oxidases with laccase activity capable to decolorize many industrial dyes in the absence of any mediators. The optimal conditions of submerged cultivation of the fungus for production of the oxidases decolorizing dyes were developed. Two unusual homodimeric oxidases with laccase activity and different physicochemical properties could be purified from the fungal culture liquid. The purified oxidases possessed individual selectivity in relation to different laccase substrates. The oxidases I and II (147 and 160 kDa, respectively) were most active under acidic conditions at elevated temperatures of 64 and 66 °C, correspondingly. The activation phenomena for the fungal oxidases during incubation in the presence of nonionic surfactants or K+ and Co2+ ions was shown. The dynamics of decolorization of malachite green in various concentrations by the fungus oxidases was studied. Based on the identified intermediates the scheme of the dye transformation by the oxidases has been presented. Being a non-toxic protein component exhibiting the decolorizing activity against a wide range of industrial dyes without additional expensive mediators, the M. ovispora VKM F-1735 oxidase has great potential for the development of new effective “green” technologies for bioremediation of water resources and soils.