Abstract
Decolorization of an anthraquinone dye (Mitui Nylon Fast Sky Blue B, SBB) by white-rot fungi, Trametes versicolor and Phanerochaete chrysosporium, was investigated in a low-nitrogen and high-carbon liquid culture. Over 90% of the dye was decolorized after the 12h-incubation with T. versicolor. On the contrary, the decolorization by P. chrysosporium occurred mainly due to biological adsorption of the dye. The production of ligninolytic enzymes, laccase and manganese peroxidase (MnP), was observed during decolorization by T. versicolor, suggesting that the decolorization of SBB is related to ligninolytic activity of white-rot fungi. Four kinds of anthraquinone dyes were treated with partially purified laccase and MnP. Decolorization of each dye by laccase was reached to more than 80%, but two dyes were not decolorized by MnP at all. These results demonstrate that laccase is the most important enzyme in decolorization and degradation of anthraquinone dyes by white-rot fungi. Toxicities of SBB before and after laccase treatment were evaluated by algal growth inhibition test using Selenastrum capricornutum. Although the dye itself showed toxicity at low concentration (2.4mg·l-1 as ErC50), the dye treated with laccase was found to be nontoxic. These findings indicate that the treatment of anthraquinone dyes with laccase is effective in decolorization and detoxification of the dyes.
