Characteristics and Potential Activity of Aerobic Denitrifying Bacteria from Fish Farming Ponds

Abstract

The presence of inorganic nitrogen in the aquaculture environment is inseparable from the nitrogen cycle. The nitrogen cycle always involves microbiological processes, including the activity of microorganisms. Denitrification is one of the main processes to reduce inorganic nitrogen content. This study aims to isolate, characterize, and measure the activity of aerobic denitrifying bacteria in eliminating inorganic nitrogen in waters. Denitrifying bacteria isolated from fish farm pond water samples by enrichment and specific medium. The nitrate reduction activity of denitrifying bacterial isolates was analyzed through the measurement of nitrate, nitrite, and gas levels. Denitrifying bacterial isolates were characterized based on colony morphology, cell shape, and Gram type. Analysis of nitrate reduction rate determined based on Michaelis-Menten kinetics. A total of 7 isolates of aerobic denitrifying bacteria were successfully isolated from enrichment medium with diverse characteristics. The percentage of nitrate reduction activity of the seven denitrifying bacterial isolates ranged from 50.48 - 87.08%. Two selected denitrifying bacterial isolates namely isolates BP8 and BP11 showed the best nitrate reduction activity of 90.14% and 88.45%. Isolates BP8 and BP11 had a maximum speed of nitrate reduction (Vmax) of 0.08 mM/hour and 0.03 mM/hour. The Michaelis-Menten constant (Km) values of isolates BP8 and BP11 were 0.35 mM and 0.44 mM. The denitrifying bacterial isolates obtained have potential as bioremediation agents for inorganic nitrogen compounds in aquaculture.