Elimination and detoxification of phenanthrene assisted by a laccase from halophile Alkalibacillus almallahensis.

Phenanthrene (Phe), a tricyclic Polycyclic Aromatic Hydrocarbon (PAH), is found in high concentrations as a pollutant in various environments. In this study, the removal or (oxidizing) ability of Phe by a laccase from Alkalibacillus almallahensis was investigated. The laccase (12 U mL−1) was able to remove 63% of Phe (50 mg L−1) under optimal conditions of 40 °C, pH 8, 1.5 M NaCl and in the presence of 1 mM HBT as a laccase mediator after a 72 h incubation period. The results for the effect of different solvents, ionic and non-ionic surfactants on the activity of the halophilic laccase towards Phe showed that the addition of these compounds increase removal efficiency and complete enzymatic removal of Phe will achieve in a solution of 5% (v/v) acetone and 1.5% tween 80. The kinetic parameters Km and Vmax of laccase-catalyzed removal of the substrate were determined as 0.544 mM and 0.882 µmol h−1 mg−1, respectively. A microtoxicity study with respect to the inhibition of algal growth showed a decrease in toxicity of the laccase-treated Phe solution. [ABSTRACT FROM AUTHOR]