New insight into the nitrogen removal capacity and mechanism of Streptomyces mediolani EM-B2

Abstract

The utilization of actinomycetes as the bioresources for heterotrophic nitrification and aerobic denitrification is rarely reported due to the lack of work to explore their nitrogen biodegradation capabilities. Streptomyces mediolani EM-B2 belonging to actinomycetes could effectively remove high concentration of multiple nitrogen forms, and the maximum removal rates of ammonium, nitrate and nitrite reached 3.46 mg/(L·h), 1.71 mg/(L·h) and 1.73 mg/(L·h), respectively. Nitrite was preferentially consumed from the simultaneous nitrification and denitrification reaction system. Nitrogen balance analysis uncovered that more than 37% of the initial total nitrogen was converted to nitrogenous gas by aerobic denitrification. Experiments with specific inhibitors of nitrification and denitrification revealed that strain EM-B2 contained ammonia monooxygenase, hydroxylamine oxidoreductase, nitrate reductase and nitrite oxidoreductase, which were successfully expressed and detected as 0.43, 0.59, 0.12 and 0.005 U/mg proteins, respectively. These findings may provide new insights into the actinomycetes for bioremediation of nitrogen pollution wastewater.

Keywords: Nitrogen balance; Simultaneous nitrification and denitrification; Specific enzymes; Specific inhibitors; Streptomyces mediolani.