Characterization on the aerobic denitrification process of Bacillus strains

Abstract

Bioenergy from biomass crops plays an important role as a promising energy source to meet the energy demands. However, during the production of biomass crops, water requirement, water quality degradation and the resulting environmental and economic problems are important factors that can affect the development of bioenergy worldwide, especially in low- and middle-income countries. In addition, industrial-scale production of bioenergy may also cause pollution to water resources. Thus, it is extremely urgent to take effective approaches to improve the waterbodies. In this study, four novel denitrifying Bacillus strains, JD-005, JD-014, JD-016 and JD-017, were isolated, characterized and further studied on the properties of nitrogen removal. The four strains could utilize ammonium, nitrate and nitrite source under aerobic conditions. In a simulated 5 L sewage bioreactor, four strains also exhibited efficient denitrification performance in multiple nitrogen coexistence, with the nitrite-N removal rates reached 0.41–1.89 mg/L/h, and the ammonium removal rates reached 0.87–2.07 mg/L/h. In addition, the denitrification metabolic pathway of Bacillus subtilis JD-014 was confirmed by investigating the nitrogen balance, gaseous nitrogen production, enzyme activity and functional genes analysis. With outstanding nitrite tolerance, the nitrogen removal efficiency could up to approximately 50–80% at initial NO2−-N concentration of 50–200 mg/L. These results showed that JD-014 should be of great potential in bioremediation of polluted waterbodies and may provide an efficient and eco-friendly way in the future to improve water resources and realize better sustainable bioenergy application.