Simultaneous removal of nitrogen and phosphorous from domestic wastewater using Bacillus cereus GS-5 strain exhibiting heterotrophic nitrification, aerobic denitrification and denitrifying phosphorous removal

A newly isolated GS-5 strain exhibiting heterotrophic nitrification, aerobic denitrification and denitrifying phosphorous removal was identified as Bacillus cereus GS-5 based on its phenotypic and phylogenetic characteristics. The isolate had exhibited efficient NH4+-N, NO3−-N, NO2−-N and PO43−-P removal from nutrient spiked real domestic wastewater with average rates of 2.62, 2.69, 1.16 and 0.42 mg L−1 h−1, respectively under aerobic condition. Metabolic inhibitor based mass balance analysis indicated that dinitrogen gas (41%), intracellular nitrogen (29%) and intracellular phosphorous (60%) were the major fates of the initial NH4+-N and PO43−-P. The successfully expression of hydroxylamine oxidase (hao), nitrate reductase (nar), nitrite reductase (nir) and poly phosphate kinase (ppk) enzyme in the cell free extracts and PCR amplification of nar, nir and ppk genes in the isolated strain provided further evidences for the nutrient removal possibility. A possible pathway of for nitrogen removal by GS-5 is suggested.