Production and Characterization of Tyrosinase Enzyme for Enhanced Treatment of Organic Pollutants in Petroleum Refinery Effluent

One of the cruel environmental quagmires confronting the Petroleum industry is the high organic pollutant levels in the bio-treatment unit of its refinery wastewater treatment plants which is not in line with the design specification. High level of organic pollutants in discharged non-compliant effluents from petroleum refineries leads to varied environmental hazards. Wastewaters discharged from petroleum refineries are characterized by the presence of toxic pollutants like phenols, polycyclic aromatic hydrocarbons (PAHs), metal derivatives, etc. Numerous enzymes from plants, fungi and bacteria have been reported to be involved in the degradation of toxic organic pollutants but with limited field trials. The present study focuses on production and characterization of enzyme, tyrosinase expressed by native microorganisms in refinery wastewater and its application in the removal of organic pollutants from petroleum refinery effluents. A total of 10 microbial strains were identified and isolated from refinery wastewater and screened for expression of tyrosinase using standard microbiological methods. Among 10 isolates, 4 isolates; Bacilus subtilis, Verticillium sp., Penicillium sp. and Aspergillus flavus were selected for enzyme characterization and production based on the magnitude of the zone of clearance they produced. Tyrosinase was produced in broth and partially purified by ammonium sulfate precipitation, dialysis and Sephadex G-75. The purified enzyme was immobilized in sodium alginate and was used for the treatment of petroleum refinery wastewater. Results revealed that the immobilized enzyme significantly removed phenol and PAHs present in the wastewater by 95 %, and 89 % respectively. These findings highlight the viability of enzyme, tyrosinase, for the degradation of organic pollutants in petroleum-derived effluents.