Aerobic denitrification by a novel Pseudomonas sp. JN5 in different bioreactor systems

Abstract

The present study evaluated the nitrate removal efficiency of a potent aerobic denitrifying bacterium in different bioreactor systems. The isolated bacterial strain characterized as Pseudomonas sp. based on biochemical and 16S rDNA sequence analysis. The strain showed an unusual ability of nitrate removal in both aerobic and anaerobic conditions, with the highest efficiency in aerobic conditions. Denitrification efficiency assessed and at low nitrate concentrations (50 mg/L), complete removal has occurred within 24 h and in high concentration (216 mg/L) removal was on 48th h of cultivation. The bacterial growth pattern was similar in all tested nitrate concentrations, and the tolerant strain JN5 could perform the aerobic denitrification at higher concentrations. In a fermenter with an initial nitrate concentration of 100 mg/L, complete removal observed within 24 h of incubation. Around 50% of nitrate removal achieved during the logarithmic growth phase of the bacterium and the remaining portion in a stationary phase under high dissolved oxygen conditions. The aerobic denitrifying efficiency of the newly isolated bacterial strain JN5 improved in a combined fermenter-packed bed reactor system with circulating batch and continuous process operations. The isolate JN5 efficiently used as an aerobic denitrifier in a bio-augmentation based system and the combinations of reactor systems improved the performance of nitrate removal by the aerobic denitrifying microorganism.