Biosynthesis of laccase by Aspergillus flavus NG85 Isolated from Saint Catherine protectorate

Characterization of Aspergillus flavus NG 85 laccase and its dye decolorization efficiency

The purified laccase of Aspergillus flavus NG85 isolated from Saint Catherine Protectorate, showed a molecular weight of 68.5 kDa. Its optimum activity obtained at enzyme concentration of 0.15 mg, substrate concentration of 10 mg/ml, temperature of 47.5 oC, pH of 5 and Km of 9.09 mg/ml. The enzyme retained 85% of its activity after 4 hours of incubation at 50 oC and 88% of its activity after 4 hours of incubation at pH 5. Copper sulfate exhibited the highest significant promotive effect on laccase activity, while sodium azide caused complete inhibition. The maximum and rapid decolorization of the purified laccase was achieved with malachite green. Among seven metallic ions tested, copper ion was the best in decolorization efficiency. Furthermore, decolorization of the real textile effluent by purified laccase predominantly occurred within the first 4 days. The putative gene for laccase was isolated, sequenced and recorded in Gene bank under accession number KM522917.2.