The Inhibitory Effects of Free Nitrous Acid on the Energy Generation and Growth Processes of an Enriched Nitrobacter Culture

Abstract

The inhibitory effects of nitrite (NO2-)/free nitrous acid (HNO2-FNA) on the metabolism of Nitrobacter were investigated using a method allowing the decoupling of the growth and energy generation processes. A lab-scale sequencing batch reactor was operated forthe enrichment of a Nitrobacter culture. Fluorescent in situ hybridization (FISH) analysis showed that 73% of the bacterial population was Nitrobacter. Batch tests were carried out to assess the oxygen and nitrite consumption rates of the enriched culture at low and high nitrite levels, in the presence or absence of inorganic carbon. It was observed that in the absence of CO2, the Nitrobacter culture was able to oxidize nitrite at a rate that is 76% of that in the presence of CO2, with an oxygen consumption rate that is 85% of that measured in the presence of CO2. This enabled the impacts of nitrite/FNA on the catabolic and anabolic processes of Nitrobacter to be assessed separately. FNA rather than nitrite was likely the actual inhibitor to the Nitrobacter metabolism. It was revealed that FNA of up to 0.05 mg HNO2-N x L(-1) (3.4 microM), which was the highest FNA concentration used in this study, did not have any inhibitory effect on the catabolic processes of Nitrobacter. However, FNA initiated its inhibition to the anabolic processes of Nitrobacterat approximately 0.011 mg HNO2-N x L(-1) (0.8 microM), and completely stopped biomass synthesis at a concentration of approximately 0.023 mg HNO2-N x L(-1) (1.6 microM). The inhibitory effect could be described by an empirical inhibitory model proposed in this paper, but the underlying mechanisms remain to be revealed.

Antimicrobial Effects of Free Nitrous Acid on Desulfovibrio vulgaris: Implications for Sulfide-Induced Corrosion of Concrete

“…Free nitrous acid (FNA), the protonated form of nitrite, was recently demonstrated to be the true metabolic inhibitor behind the usually observed nitrite inhibition (11). In recent treatment of sewer biofilms, it was seen that application of FNA for 6 to 24 h at 0.2 to 0.3 mg N/liter decreased the live cell percentage from about 80% to 5 to 15% (3).…”

Simultaneous Elimination of Carbon and Nitrogen Compounds of Petrochemical Effluents by Nitrification and Denitrification

“…It has been observed that high concentrations of nitrite can inhibit the nitrification process and that could be mainly related to the pH values through the formation of HNO 2 . Nitrous acid is known to inhibit nitrification, thus, low pH values must be avoided in nitrifying processes (Anthonisen et al, 1976;Vadivelu et al, 2006aVadivelu et al, , 2006b. Recently, Silva et al (2011) reported that the nitrite-oxidizing process was more sensitive to the presence of nitrite than the ammonium-oxidizing process, suggesting that nitrite accumulation in nitrification systems should be controlled to avoid a higher accumulation of nitrite and a decrease in nitrate yield.…”

Producing free nitrous acid – A green and renewable biocidal agent – From anaerobic digester liquor

“…It has been reported that, at parts per billion (ppb) levels, FNA has inhibitory effects on: 1) the anabolic and catabolic activities of ammonia and nitrite oxidising bacteria [2,3]; 2) growth, nitrate and nitrite reduction activities of denitrifying bacteria in activated sludge [4] and 3) aerobic and anoxic phosphorus uptake by polyphosphate accumulating organisms [5,6]. In addition, FNA has also been shown to inhibit methanogens [7], pathogens [8] and yeast [9].…”