Application of Pseudomonas putida PpG 786 Containing P‐450 Cytochrome Monooxygenase for Removal of Trace Naphthalene Concentrations

This study explores the potential for a bacterial monooxygenase to remove polynuclear aromatic hydrocarbons from aqueous solutions at high rates. This is part of a larger effort to test the versatility of the cytochrome P‐450cam monooxygenase enzyme system for detoxification of industrial process wastewaters that contain trace quantities of hazardous compounds like PAHs or halocarbons. The intracellular concentration of P‐450cam in washed, resting cell suspensions of Pseudomonoas putida PpG 786 that were cultured on camphor was measured by adapting a spectrophotometric method used to measure P‐450 concentration in extracts of mammalian tissues. Naphthalene removal in the suspensions was measured as a function of incubation time, biomass concentration, starting naphthalene concentration (3‐180 μmol/L) and in the presence of known P‐450 inhibitors. Involvement of the P‐450cam system in the measured naphthalene disappearance was established by showing that while significant naphthalene removal occurred in camphor‐grown biomass, no disappearance was observed in glutamate‐grown biomass and that removal was turned off in the presence of the P‐450 inhibitor metyrapone. The half‐life of naphthalene removal for a 1 ppm solution (7.8 μM) was about 18 h. The fraction of naphthalene removed descreased rapidly as initial naphthalene concentration increased, and essentially no naphthalene was removed when the starting concentration exceeded 189 μmol/L (23 ppm).