A sensitive method for naphthalene oxygenase assay in whole cells

The naphthalene oxygenase activities of strains degrading this compound are frequently low. Spectrometric methods allow determination only down to a minimum of 10 nmol/min/mg protein. Difficulties also result from the fact that the measurements mostly require whole cells, which involves a high background signal. We developed a new sensitive method which enables high cell concentrations to be used because the naphthalene is determined after extraction from the reaction mixture with cyclohexane. This approach has other advantages which are discussed. The method was applied to different strains which degrade naphthalene at varying rates and to a community. The values determined coincided with those calculated from the rate of oxygen consumption.