EFFECTS OF OXYGEN, PH AND NITRATE CONCENTRATION ON DENITRIFICATION BY PSEUDOMONAS SPECIES

The production of nitrogen-containing gases by denitrification in three organisms was examined using membrane inlet mass spectrometry. The effects of O-2 (during both growth and maintenance) and of pH, nitrate concentration and carbon source were tested in non-proliferating cell suspensions. Two strains of Pseudomonas aeruginosa were capable of co-respiration of NO3- and O-2 and, under controlled O-2 supply, gave oscillatory denitrification. Variations in culture and assay conditions affected both the rate of denitrification and the ratio of end products (N2O:N-2). Higher rates were seen following anaerobic growth. Optimum values of pH and nitrate concentration for denitrification are given. Generally, the optimum pH was 7.0-7.5, approximately that of the growth medium. Optimum nitrate concentration was generally 20 mM.