Aerobic nitrification and denitrification among heterotrophic bacterial isolates

In addition to being an integral part of the planet’s nitrogen cycle, bacterially facilitated nitrification is a process of great commercial importance in the wastewater treatment, aquaculture and agronomy industries. Twelve distinct species of heterotrophic bacteria, belonging to the genera Bacillus, Pediococcus and Lactobacillus, were isolated from BiOWiSH’s commercially available water treatment products (Aqua, Aqua FOG, AquaFarm). These isolates were then examined for aerobic nitrification activity using colorimetric analysis of ammonia (via a modified Berthelot reaction), nitrite and nitrate (via a modified Griess reaction). Rates of aerobic ammonia degradation ranged from 0.927 ppm h-1 to 5.89 ppm h-1 in wastewater reactor flasks. The use of heterotrophic, aerobic bacteria in water treatment systems may present economic advantages as well as novel biological management of undesirable nitrogenous intermediates. Introduction The biological removal of inorganic nitrogenous compounds, such as ammonia (NH4 +) and nitrate (NO3 -) from aquatic systems has long been a topic of interest for wastewater engineers and other water treatment professionals. These compounds contribute to eutrophication and are toxic to many aquatic organisms; therefore their presence in treated wastewater and in clean water systems, such as ponds, lakes, and reservoirs, is undesirable (Shannon et al, 2008). In the past, combinations of autotrophic nitrifying and denitrifying bacteria (which convert NH4 + to N2, with NO3 as an intermediate) were believed to be the only method for effecting such remediation. However, the discovery of novel metabolic pathways among several bacterial taxa during the latter part of the 20th century forced a reevaluation of this paradigm (Schmidt et al, 1987). Scheme 1 – Diagram of the microbial nitrogen cycle which visualizes the various metabolic pathways through which bacteria convert NH4 + to N2. Dashed lines indicate pathways generally carried out in the presence of oxygen, whereas solid lines indicate pathways generally believed to be anoxic (Schreiber, 2009). Research Study