Analyzing Simultaneous Heterotrophic Nitrification and Aerobic Denitrification Potential of a Newly Isolated Bacterium, Bacillus cereus strain GS5 SND by Newly Isolated Bacillus cereus GS5 strain

* Abstract-The present study aims in investigating simultaneous heterotrophic nitrification and aerobic denitrification (SND) ability of a newly isolated bacterium. The bacterial strain GS5 was isolated from a laboratory scale denitrifying bioreactor and characterized. Based on phenotypic and phylogenetic characteristics as derived from partial 16S rRNA gene sequence, the isolate was identified to be Bacillus cereus GS5 strain (Gen Bank accession no. KM212993). The strain had exhibited the capability of utilizing ammonia, nitrate and nitrite as sole nitrogen sources in presence of external carbon sources, thus heterotrophic in nature. Considering, initial concentration of ammonium as 50 mg/L, 92.02% was removed after 24h incubation with little accumulation of the intermediates such as hydroxylamine, nitrite, and nitrate. Similarly, the new isolate had a high denitrifying ability, from initial 100 mg/L nitrate, 98.26% was removed in a 24h period under aerobic conditions, with reduced level of nitrite accumulation (0.613 mg/L). Thereby, confirming aerobic denitrification. Gas production as a result of denitrification process was indicated by the presence of gas bubbles in the Durham tubes and on the surface of the microbial culture broth. The results illustrated that the optimum aerobic denitrification conditions for strain GS5 were, a C/N ratio of 3.5, incubation temperature of 35 °C, an initial pH of 7, and rotation speed of 125 rpm (dissolved oxygen 2.75-3 mg/L). Therefore, the new isolate Bacillus cereus GS5 strain, with aerobic heterotrophic nitrification-denitrification ability, can be used in full scale treatment systems for facilitating simultaneous nitrification and denitrification (SND) in order to remove nitrogen from contaminated water.