Nitrate as electron acceptor

A facultative autotroph (lithotroph) strain MLHE-1 was able to oxidize arsenite under anaerobic conditions to arsenate using nitrate as electron acceptor (Oremland et al. 2002). 

Bacteria have been isolated using reduced anthraquinone-2,6-disulfonate (HjAQDS) as electron donor and nitrate as electron acceptor (Coates et al. 2002). The organisms belonged to the a-, p-, y-, and 5-subdivision of the Proteobacteria, and were able to couple the oxidation of H AQDS to the reduction of nitrate with acetate as the carbon source. In addition, a number of C2 and C3 substrates could be used including propionate, butyrate, fumarate, lactate, citrate, and pyruvate. 

The growth of Bacillus subtilis may take place under a variety of conditions (a) aerobic conditions, (b) using nitrate as electron acceptor, and (c) fermentative conditions with glucose provided pyruvate is available as an electron acceptor since the organism lacks pyruvate formate hydrogen lyase (Nakano and Zuber 1998). 

The genus Thiobacillus, especially the species T. denitrificans catalyzed the oxidation reactions of hydrogen sulfide yielding soluble hydrosulfide compounds, elemental sulfur, and sulfuric acid. Carbonyl sulfide and carbon disulfide are converted to hydrogen sulfide by hydrolysis. Additionally, they are oxidized to SOx and sulfates via microbial action. The reported oxidation reactions of thiosulfate using nitrate as electron acceptor are ... 

The corresponding anoxic process, using nitrate as electron acceptor and ending the process by formation of N2, is (cf. Examples 2.2 and 2.4) ... 

It is important to notice that Equation (5.13) is valid for the relation between oxygen and nitrate as electron acceptors in aerobic and anoxic processes, respectively. These processes thereby relate to a corresponding transformation of organic matter as electron donor. In addition to the transformation of organic matter in the redox processes, organic matter is also used for the production of heterotrophic biomass. 

A fundamental requirement for using a sewer as a treatment system followed by subsequent physicochemical or mechanical treatment is often the installment of aerators. Contrary to what has been proposed by a number of authors, the limitation in using the sewer as a treatment system is normally not the biomass. Addition (circulation) of activated sludge is, therefore — except for cases with excessive aeration — in general, of no interest. Substitution of oxygen with nitrate as electron acceptor is possible, but a reduced rate of transformation is expected. 

Groundwater and Soil. Pumping out the liquid phase is an obvious first step if die contaminant is likely to be mobile, but in situ bioremediation is a promising option. Thus, the U.S. Department of Energy is investigating the use of anaerobic in situ degradation of carbon tetrachloride with nitrate as electron acceptor, and acetate as electron donor. 

The anaerobic oxidation of ammonia can be an important process in the absence of oxygen, if nitrite as an alternative electronacceptor is available. Nitrite does usually not accumulate in high concentrations but may be continuously delivered by bacteria using nitrate as electron acceptor for the oxidation of organic carbon. Thus, anammox... 

Dissimilatory reduction of nitrate to ammonia is performed by obligate and facultative anaerobes with fermentative metabolism, including Clostridium and Bacillus species (Tiedje, 1988). These organisms, in contrast to denitrifiers, usually do not rely on nitrate as electron acceptor. Therefore, DNRA involves 8e transfer as compared to 5e transfer for denitrification, suggesting that more organic substrate can be potentially degraded by DNRA. However, nitrate availability under DNRA conditions is usually very low because much of the nitrate formed during nitrification under aerobic conditions is rapidly consumed by denitrifiers in adjacent anaerobic environments. 

In recent years, availability of modem tools inclnding oxygen and ion-specific electrodes, culture vessels, and analytical methods has made it possible to determine the environmental conditions that support denitrification. These studies have shown that it is possible that a group of bacteria (mostly heterotrophic nitrifiers) are able to simultaneously utilize oxygen, nitrite, or nitrate as electron acceptors, even when oxygen levels in cultures approach near saturation levels (Zehr and Ward,... 

Certain species of Enterobacteriaceae, especially 0. proteus, could utilise nitrates as electron acceptors for anaerobic respiration, resulting in reduction of nitrate into nitrite. Nitrite further could possibly react with secondary amines present in the wort, forming (V-nitrosoamine (Figure 8.2). A -nitrosomines are carcinogenic in nature (Smith, 1994). Hence, a considerable amount of apparent total N-nitroso compounds (ATNCs) represents a possible risk to health, and consequently their concentration is strictly monitored and limited to 20 gg/1 (Maiguerite and Walker, 2002). Because of the risk of W-nitroso compounds, the Enterobacteriaceae species related to brewery environments are monitored. 

Emanuelsson, E. A. C. and Livingston, A. G. 2002. Study of membrane attached biofilm performance with nitrate as electron acceptor. Desalination, 149,211-215. 

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