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Cultivation and Conversion of Algae for Wastewater Treatment and Biofuel Production
Published in Sonil Nanda, Prakash Kumar Sarangi, Dai-Viet N. Vo, Fuel Processing and Energy Utilization, 2019
Priyanka Yadav, Sivamohan N. Reddy, Sonil Nanda
Microalgae assimilated the fixed N2 as ammonium-nitrogen, nitrate-nitrogen, and nitrite-nitrogen. The assimilation of nitrogen requires its reduction to ammonium-nitrogen in a two-step process in the presence of nitrate and nitrite reductases enzymes. In the initial step, the nitrate-nitrogen reduces to nitrite-nitrogen by the nitrate reductase enzyme in the presence of NADPH as a reducing agent. Furthermore, nitrite-nitrogen is reduced to ammonium-nitrogen by the nitrite reductase enzyme, which further uses ferredoxin to catalyze the electron transfer reactions. Ammonium-nitrogen formed by the reduction of nitrate-nitrogen and nitrite-nitrogen is further converted into amino acids by the glutamine synthetase-glutamate synthase pathway in the presence of the glutamine synthase enzyme. Phosphorus enters microalgae cells through the plasma membrane in the form of HPO42− and H2PO4−. Further, phosphate-phosphorus is converted into organic compounds by processes such as phosphorylation, oxidative phosphorylation, and photophosphorylation. In these processes, adenosine diphosphate (ADP) is converted into ATP by an energy input (Martinez et al. 1999).
Nitrogen Cycle Bacteria in Agricultural Soils
Published in Vivek Kumar, Rhizomicrobiome Dynamics in Bioremediation, 2021
Guillermo Bravo, Paulina Vega-Celedón, Constanza Macaya, Ingrid-Nicole Vasconez, Michael Seeger
Denitrification Denitrification is a process in which nitrate is reduced successively to NO, N2O and N2 gases. Nitrate reduction by anaerobic microorganisms uses nitrate as electron acceptor. Nitrate reduction starts with the action of the transmembrane nitrate reductase, whose product is nitrite. Nitrite is then reduced to nitric oxide by nitrite reductase. Nitric oxide is successively reduced to gaseous nitrogen (Rütting et al. 2018). Denitrification can be harmful to soils. It has been shown that 17 Tg of N are lost worldwide every year from soils and 15 Tg at the agroecological level due to the microbial denitrifying activity (Mosier et al. 2004, Mao et al. 2011).
Introduction
Published in Moustafa Samir Moussa, Nitrification in Saline Industrial Wastewater, 2014
In contrast to denitrification, the process of dissimilatory nitrate reduction to ammonia (DNRA) does not have N2 but NH4+ as final product. Apart from a nitrate reductase, a nitrite reductase, which reduces nitrite to ammonia, is involved in this process. Denitrification and DNRA can occur simultaneously and DNRA can be of quantitative importance in environments with high carbon/nitrate ratio or high sulphide concentration (Brunet and Garcia-Gil 1996; Cole 1996; Simon 2002).
Research advances in anammox granular sludge: A review
Published in Critical Reviews in Environmental Science and Technology, 2022
Mabruk Adams, Junxiang Xie, Arthur wendinso Judicael Kabore, Yaofeng Chang, Jiawei Xie, Menglei Guo, Chongjun Chen
Cu is an essential component of nitrite reductase of AnAOB (Hira et al., 2012). The IC50 of Cu2+ on the anammox activity is reported to be in the range of 1.9–12.9 mg L−1 (Lotti et al., 2012). Similarly, in investigating the long-term effects of Cu2+ on the anammox process, it was observed that a 5 mg L−1 concentration could strongly inhibit the anammox activity reducing it by about 94% (Kang & Zheng, 2019). Accordingly, due to the influence of Cu2+, the anammox sludge had a lower settling velocity and a larger diameter. Observations by electron microscope revealed that Cu2+ could induce EPS secretion and cause cell membrane damage (Zhang, Zhang et al., 2015). The joint long-term application of Cu and Zn has also been reported to have resulted in a similar outcome (Kang & Zheng, 2019). This causes the AnAOB to shrink and large amounts of precipitation around aggregates (Zhang, Zhang et al., 2015).
Denitrification-induced carbonate precipitation by bio-composite material with Pseudomonas aeruginosa for simultaneous nitrate and cadmium remediation
Published in Human and Ecological Risk Assessment: An International Journal, 2023
Chaolin Fang, Ruitao Lin, Kaixuan Xu, Varenyam Achal
At the same time, BCM containing P. aeruginosa was able to produce higher nitrite reductase compared to nitrate reductase. The maximal nitrite reductase activity was found at 18 h (0.062 U/mg protein) (Figure 6). It also supports the reason behind insignificant accumulation of nitrite throughout the process (Figure 2). It is noteworthy that in solution, nitrite can generate free nitrous acid that has high biological toxicity and inhibits the growth and metabolism of microorganisms. Thus, the nitrite reductase enzyme that could convert nitrite immediately to less toxic nitric oxide played a crucial role in the denitrification process (Miyahara et al. 2010).
Enhancement of growth and biomolecules (carbohydrates, proteins, and chlorophylls) of isolated Chlorella thermophila using optimization tools
Published in Preparative Biochemistry & Biotechnology, 2022
Sambit Sarkar, Jaivik Mankad, Nitin Padhihar, Mriganka Sekhar Manna, Tridib Kumar Bhowmick, Kalyan Gayen
In this study, nitrate was found to impart a negative effect on biomass synthesis. This result is similar to another study conducted with Asterarcys sp. where 0.375 g/L of nitrate concentration in the media provided higher biomass concentration than other concentrations of nitrates.[16] Similar results were obtained in another study where an increase in nitrate concentration decreased the biomass production and the highest biomass was obtained at the lowest nitrate concentration used in that study (1.5 g/L).[44] However, nitrogen in a form of urea was shown to boost the growth in Chlorella spp.[19] Microalgae cells necessitate nitrogen in a higher amount owing to its role as the critical constituent of proteins, peptides, chlorophylls, enzymes, ATP, RNA, DNA, and other cellular constituents.[45] Nitrogen in form of nitrate, nitrite, and ammonium are directly assimilable in the metabolic activity of microalgae. However, nitrate is comparatively stable thermodynamically than other forms of nitrogen that get oxidized in the aqueous medium. Nitrate after being translocated across plasmalemma requires to be chemically reduced to ammonium for being assimilated into the cell. Chemical reduction of nitrate is governed by two enzymes which are nitrate reductase and nitrite reductase.[46] Nitrate reductase catalyzes the bi-electron transfer in the cytosol with the aid of NADPH. The enzyme nitrate reductase is attached with the pyridine nucleotide oxidation in microalgae.[44] Nitrite reductase reduces nitrite in a reaction of six-election transfer. Nitrite reductase localized in the chloroplast uses ferredoxin which is sourced from the photosynthetic electron flow in microalgae. Ammonium is mostly incorporated into amino acids by the chronological act of glutamine synthetase (GS) and glutamine 2 oxoglutarate aminotransferase (GOGAT). Ammonium is assimilated by GS in an irreversible reaction utilizing glutamate as substrate. GS and GOGAT are usually located in the chloroplast. However, their isoenzymes may also be found in the cytosol. Glutamate synthase facilitates the synthesis of amino acids through transamination after being transported to cytosol from chloroplast.[44]