Homogeneously catalytic oxidation of phenanthrene by the reaction of extracellular secretions of pyocyanin and Nicotinamide Adenine Dinucleotide

Application of biological methods on polycyclic aromatic hydrocarbons (PAHs) treatment is always limited by its low degradation efficiency. In this work, a catalytic oxidation pathway of phenanthrene resulted by extracellular secretions of P. aeruginosa NY3 was proposed. Results of the in vitro experiments showed that, the extracellular secretions of Pyocyanin (Pyo) and Nicotinamide Adenine Dinucleotide (NADH) acted as homogeneous catalysts because which produced H2O2, hydroxyl free radical and superoxide anion radical continuously under aerobic conditions. These produced reactive oxygen species oxidized the phenanthrene in aqueous solution, leading to the cleavage of the phenanthrene ring and the formation of phthalates products and low molecular weight metabolites (such as alkanoic acids). The ratio of BOD5/COD of phenanthrene-containing wastewaters was greatly improved after treating with Pyo and NADH. Results of the in vivo experiments showed that, predegradation of phenanthrene by extracellular fluid simultaneously containing Pyo and NADH, promoted cell growth of P. aeruginosa NY3, which confirmed the improvement of bioavalability of phenanthrene-containing wastewaters by the catalytic oxidation of Pyo and NADH. Further details of the free radical detection indicated that, the increase in secretion of Pyo by a bacterium was favorable to the production of H2O2 in the extracellular fluid.