Transformation and degradation of the disazo dye Chicago Sky Blue by a purified laccase from Pycnoporus cinnabarinus

The degradation of the disazo dye Chicago Sky Blue 6B by a purified laccase from Pynoporus cinnabarinus was investigated. Laccase was purified to homo geneity and characterized. The enzyme had a molecular size of 63 kDa as det ermined by SDS-PAGE and an isoelectric point at pH 3. Amino acid compositio n and N-terminal amino acid sequence was shown to be similar to other funga l laccases. The purified laccase was stable for 1 h at 60 degrees C and was irreversibly inactivated by sodium azide at 0.1 mM. Laccase was shown to i nitiate destruction of the chromophore of the disazo dye Chicago Sky Blue, resulting in the formation of two intermediate products with absorption int ensities about one order of magnitude lower than the parent molecule. The r ate at which the dye was transformed by purified laccase was shown to incre ase with increasing concentrations of the enzyme. (C) 2000 Elsevier Science Inc. All rights reserved.