The effect of nitrate and ammonium ions on kinetics of diesel oil degradation by Gordonia alkanivorans S7

The process of degradation of diesel oil hydrocarbons by aerobic denitrifying bacterial strain Gordonia alkanivorans S7 in media containing either nitrate or/and ammonium ions was studied. Experiments were carried out at high concentration of dissolved oxygen and high hydrocarbons contents. Microbial growth, rate of hydrocarbons biodegradation, respiratory activity of cells, critical oxygen concentration, ammonium and nitrate ions uptake were determined. Although there was no significant difference in biomass production in media with nitrate or ammonium ions, the values of respiratory activity and degree of hydrocarbon consumption were considerably higher in the presence of nitrate ions what could result from co-respiration, which occurred in presence of both nitrate and oxygen. In nitrate-containing medium, values of critical oxygen concentration in the last days of culture were lower than in the medium with ammonium ions. Results obtained in culture with NH4NO3 show that ammonium ions may cause the suppression of nitrate ions uptake. Conclusions of the work indicate the need for preliminary experiments before beginning full-scale bioremediation processes to find the suitable form and concentration of nitrogen source to stimulate growth of aerobic denitrifiers. The strain G. alkanivorans S7 is a new example of aerobic denitrifier, application of which can provide benefits for biodegradation of diesel oil hydrocarbons.