Magnetic cross-linked laccase aggregates - Bioremediation tool for decolorization of distinct classes of recalcitrant dyes

The increasing use of laccase in waste water industries is useful to explore the high benefit/cost ratio of insolubilization technologies like cross linked enzyme aggregates (CLEAs) for the decolorization and detoxification of distinctive classes of recalcitrant dyes. Amino-functionalized magnetic nanoparticles bonded to CLEAs increased the potential of laccase-based CLEAs and are applicable for commercial implementation of this technology in environmental applications. The activity recovery obtained from the stable rigid structure of magnetic CLEAs was around 32%. High volumetric activity, increased in thermal and operational stability of laccase and its resistance to extreme conditions were the properties provided by these magnetic CLEAs. Kinetic studies show that the catalytic efficiency of the enzyme, based on the k(cat)/k(m) value, changed significantly upon CLEAs and magnetic CLEA formations. When 0.2 U/mL of magnetic CLEAs was used, the biocatalyst rapidly decolorized 61-96% of remazol brilliant blue R, malachite green and reactive black 5 initially at 50 mg L-1 at 20 degrees C and pH 7.0. Investigation of dye degradation using both active and heat denatured CLEAs revealed a slight adsorption of dyes on inactivated biocatalysts. A laboratory scale perfusion basket reactor (BR) was used to study the continuous decolorization of dyes. The efficient decolorization (>90%) of remazol brilliant blue R and slight decrease in CLEA activity were measured over a 10 h period of continuous operation, which illustrates the potential of CLEAs for the wastewater treatment. The present findings will advance the understanding of dye decolorization mechanism by CLEA laccase, which could provide useful references for developing industrial wastewater treatment. (C) 2014 Elsevier B.V. All rights reserved.