Laccase Production Under Optimized Parameters by Aspergillus oryzae, an Endophytic Fungus and their Application to Waste Water Treatment

Abstract

Objective: To isolate an endophytic fungal laccase producer from the Ziziphus mauritiana plant leaves in the surroundings of paper mill effluents and to study its role in the decolorization of synthetic dyes, removal of COD and phenol from industrial effluents. Methods: Laccase-producing endophytic fungi were isolated and screened by using an agar plate method. The positive isolates were identified, and laccase activity was determined by using spectrophotometric methods to monitor the oxidation of guaiacol and optimizing various parameters affecting laccase production. The molecular mass of the purified laccase enzyme was determined by using 12% SDSgel electrophoresis. Industrial effluents were treated with laccase to remove phenol, decolorize dyes, and reduce chemical oxygen demand. For the analysis, a spectrophotometric method was employed. Findings: One of the most effective endophytic fungal isolates, Aspergillus oryzae, was screened as a maximum laccase producer. The optimal pH of 6, temperature of 35 o C, inoculation period of 8 days, and the inoculum number of 3 discs/100 ml of Czapek Dox Broth in submerged culture were determined for the maximum laccase production. Sucrose and sodium nitrate, as carbon and nitrogen sources, considerably assisted laccase production. The molecular weight of the isolated laccase from A. oryzae was 66 kDa. The greatest activity was determined to be 64.2 U/mL, which is two times more than under unoptimized conditions. After the fifth day of exposure, the A. oryzae laccase decolorizes the synthetic dyes Bromophenol blue, Congo red, Methyl orange, and Phenol red.Chemical oxygen demand and phenolic pollutants' clearance rates were 38-43% and 60% from coal and textile effluents during their exposure times, respectively. Novelty: A. oryzae was discovered to be a potent natural laccase producer endophytic fungus from paper mill effluents, which may be used for decolorizing non-textile dyes, treatment of various industrial effluents, and other industrial purposes.