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Open Access Research

Biocatalytic potential of laccase-like multicopper oxidases from Aspergillus niger

Juan Antonio Tamayo-Ramos1, Willem JH van Berkel2 and Leo H de Graaff1*

Author Affiliations

1 Microbial Systems Biology, Laboratory of Systems and Synthetic Biology, Wageningen University, Dreijenplein 10, Wageningen, 6703 HB, The Netherlands

2 Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, Wageningen, 6703 HA, The Netherlands

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Microbial Cell Factories 2012, 11:165  doi:10.1186/1475-2859-11-165

Published: 27 December 2012

Abstract

Background

Laccase-like multicopper oxidases have been reported in several Aspergillus species but they remain uncharacterized. The biocatalytic potential of the Aspergillus niger fungal pigment multicopper oxidases McoA and McoB and ascomycete laccase McoG was investigated.

Results

The laccase-like multicopper oxidases McoA, McoB and McoG from the commonly used cell factory Aspergillus niger were homologously expressed, purified and analyzed for their biocatalytic potential. All three recombinant enzymes were monomers with apparent molecular masses ranging from 80 to 110 kDa. McoA and McoG resulted to be blue, whereas McoB was yellow. The newly obtained oxidases displayed strongly different activities towards aromatic compounds and synthetic dyes. McoB exhibited high catalytic efficiency with N,N-dimethyl-p-phenylenediamine (DMPPDA) and 2,2-azino-di(3-ethylbenzthiazoline) sulfonic acid (ABTS), and appeared to be a promising biocatalyst. Besides oxidizing a variety of phenolic compounds, McoB catalyzed successfully the decolorization and detoxification of the widely used textile dye malachite green.

Conclusions

The A. niger McoA, McoB, and McoG enzymes showed clearly different catalytic properties. Yellow McoB showed broad substrate specificity, catalyzing the oxidation of several phenolic compounds commonly present in different industrial effluents. It also harbored high decolorization and detoxification activity with the synthetic dye malachite green, showing to have an interesting potential as a new industrial biocatalyst.

Keywords:
Aspergillus; Multicopper oxidase; Laccase; Bioremediation; Decolorization