DECOLORATION OF THE DIAZO DYE REACTIVE BLACK 5 BY IMMOBILISED Bjerkandera adusta IN A STIRRED TANK BIOREACTOR

Martina Mohorčič,^a Jožefa Friedrich,^a* and Aleksander Pavko^b
aNational Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia
^bFaculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, 1000 Ljubljana, Slovenia

Abstract
Decoloration of the synthetic textile dye Reactive Black 5 by the cultivated fungi, Bjerkandera adusta, Irpex lacteus, and Hypoxylon fragiforme was studied. The most effective fungus in shaken flask experiments was B. adusta, which was able to decolorise the dye from black-blue to a yellow color in less than 10 days. This fungus was chosen for cultivation in a 5 L stirred tank bioreactor with immobilised mycelium. Here decoloration of the dye in an initial concentration of 0.2 g/L from black-blue to intense yellow was reached in 20 days. Considering the spectral absorption coefficients at three different wavelengths, the final liquid was decolorised to an almost ecologically acceptable degree. Measurement of activities of the oxidative enzymes laccase, lignin peroxidase, manganese dependent- and manganese independent peroxidases showed that initially lignin peroxidases and subsequently manganese dependent peroxidases are presumably responsible for the decoloration of the diazo dye Reactive Black 5 by B. adusta.

Key words: diazo dye, Reactive Black 5, decoloration, ligninolytic fungi, Bjerkandera adusta, peroxidases, stirred tank bioreactor, immobilised biomass, bioremediation