Biodegradation of Dyes by Laccase from Isolated Strain Aspergillus flavus PUF5

Abstract

Synthetic dyes are very difficult to degrade for their complex structure. During dyeing process in industry, a huge amount of dyes are lost as effluents. Degradation of these effluents by physical and chemical processes is the most problematic issues nowadays. Enzymatic oxidation of these dyes using oxidoreductase such as laccase has received a great attention in recent years for decolorization of dyes in effluent. In the present study, an isolated fungus Aspergillus flavus PUF5 was used to produce laccase enzyme and employed for degradation of five commercially used textile dyes, phenol red, methyl orange, malachite green, bromophenol blue and Congo red. The investigations were made with the effect of redox mediators (1 mM), temperature (25–45 °C), pH (4–8) and incubation time (0–24 h) in the dye decolorization by laccase. Highest efficiency in dye decolorization was found with redox mediator 1-hydroxy-benzotriazole (HBT). The interactions between four variable factors were statistically studied using response surface methodology. Optimized states of selected variables were dye concentration (6.04 µM), enzyme concentration (78.8 U/ml), pH (5.6) and redox mediator (1.07 mM) with predicted and observed activity of laccase 85.94 and 86.3 U/ml, respectively. These results suggest that laccase is a potential enzyme for removal of dyes present in wastewater of textile industry.