Health & Environmental Research Online (HERO)


Ammonia


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The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Free nitrous acid selectively inhibits and eliminates nitrite oxidizers from nitrifying sequencing batch reactor

Authors: Kim, DJ; Seo, DW; Lee, SH; Shipin, O (In Press) Bioprocess and Biosystems Engineering. HERO ID: 838936

[Less] In a complete nitrification sequencing batch reactor (CNSBR), where ammonium containing wastewater (200-1,000 mg N/L) . . . [More] In a complete nitrification sequencing batch reactor (CNSBR), where ammonium containing wastewater (200-1,000 mg N/L) is completely oxidized to nitrate up to 2.4 kg NH(4) (+)-N/m(3) d, both ammonia oxidizers and nitrite oxidizers were enriched in the sludge granules. Quantitative fluorescence in situ hybridization analyses of the sludge granules of the CNSBR showed that ammonia oxidizers and nitrite oxidizers occupied 31 and 4.2% of total bacteria, respectively. Most of the nitrite oxidizers were Nitrobacter species (95% of the nitrite oxidizers) and the remainder was Nitrospira species. The population of nitrite oxidizers was significantly higher than that of partial nitrification SBR (PNSBR) where most of the ammonium was oxidized to nitrite. The PNSBR had 37% (ammonia oxidizers) and 0.4% (nitrite oxidizers) of total bacteria. Comparative study with CNSBR and PNSBR revealed that free nitrous acid, rather than free ammonia, played a critical inhibition role to wash out nitrite oxidizers from the reactor. The concentrations of free ammonia and nitrite as well as free nitrous acid in the CNSBR selected Nitrobacter as the dominant nitrite oxidizers rather than Nitrospira.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Crystal structure of the complex between 4-hydroxybutyrate CoA-transferase from Clostridium aminobutyricum and CoA

Authors: Macieira, S; Zhang, J; Buckel, W; Messerschmidt, A (In Press) Archives of Microbiology. HERO ID: 1000059

[Less] Clostridium aminobutyricum ferments 4-aminobutyrate (γ-aminobutyrate, GABA) to ammonia, acetate and . . . [More] Clostridium aminobutyricum ferments 4-aminobutyrate (γ-aminobutyrate, GABA) to ammonia, acetate and butyrate via 4-hydroxybutyrate that is activated to the CoA-thioester catalyzed by 4-hydroxybutyrate CoA-transferase. Then, 4-hydroxybutyryl-CoA is dehydrated to crotonyl-CoA, which disproportionates to butyryl-CoA and acetyl-CoA. Cocrystallization of the CoA-transferase with the alternate substrate butyryl-CoA yielded crystals with non-covalently bound CoA and two water molecules at the active site. Most likely, butyryl-CoA reacted with the active site Glu238 to CoA and the mixed anhydride, which slowly hydrolyzed during crystallization. The structure of the CoA is similar but less stretched than that of the CoA-moiety of the covalent enzyme-CoA-thioester in 4-hydroxybutyrate CoA-transferase from Shewanella oneidensis. In contrast to the structures of the apo-enzyme and enzyme-CoA-thioester, the structure described here has a closed conformation, probably caused by a flip of the active site loop (residues 215-219). During turnover, the closed conformation may protect the anhydride intermediate from hydrolysis and CoA from dissociation from the enzyme. Hence, one catalytic cycle changes conformation of the enzyme four times: free enzyme-open conformation, CoA+ anhydride 1-closed, enzyme-CoA-thioester-open, CoA + anhydride-2-closed, free enzyme-open.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

A Mechanistic Analysis of the Birch Reduction

Author: Zimmerman, HE (In Press) Accounts of Chemical Research. HERO ID: 1000903

[Less] The Birch Reduction is one of the main reactions of organic chemistry. The reaction involves the reaction . . . [More] The Birch Reduction is one of the main reactions of organic chemistry. The reaction involves the reaction of dissolving metals in ammonia with aromatic compounds to produce 1,4-cyclohexadienes. Discovered by Arthur Birch in 1944, the reaction occupies 300 pages in Organic Reactions to describe its synthetic versatility. Thus, it is remarkable that the reaction mechanism has been so very controversial and only relatively recently has been firmly established. Perhaps this is not that surprising, since the reaction also has many unusual and esoteric mechanistic facets. Here, I provide a description of how I have applied ever-evolving levels of quantum mechanics and a novel experimental test to understand details of the mechanism and the origins of the selectivities observed in the Birch reduction. The reaction involves an initial radical anion resulting from introduction of an electron from the blue liquid ammonia solution of free electrons formed by the dissolution of Li or related metals. This radical anion is protonated by an alcohol and then further reduced to a carbanion. Finally, the carbanion is protonated using a second proton to afford a nonconjugated cyclohexadiene. The regiochemistry depends on substituents present. With 18 resonance structures in the case of anisole radical anion, prediction of the initial protonation site would seem difficult. Nevertheless, computational methods from Hückel theory through modern density functional calculations do correctly predict the site of protonation. An esoteric test established this mechanism experimentally. The nature of the carbanion also is of mechanistic interest, and the preponderance of the resonance structure shown was revealed from Hückel calculations involving variable bond orders. For the trianion from benzoic acid, parallel questions about structure are apparent, and have been answered. Some mechanistic questions are answered experimentally and some by modern computations. Recently, our mechanistic understanding has led to a variety of synthetic applications. For example, the preparation of alkyl aromatics from benzoic acids makes use of the intermediates formed in these reactions. This Account provides an overview of both experimental techniques and theoretical methodology used to provide detailed mechanistic understanding of the Birch Reduction.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Synthesis and Application of a New Fluorous-Tagged Ammonia Equivalent

Authors: Nielsen, SD; Smith, G; Begtrup, M; Kristensen, JL (In Press) Chemistry: A European Journal. HERO ID: 990682

[Less] A novel fluorous-tagged ammonia equivalent has been developed. It is based on a nitrogen-oxygen bond, . . . [More] A novel fluorous-tagged ammonia equivalent has been developed. It is based on a nitrogen-oxygen bond, which can be cleaved in a traceless manner by a molybdenum complex or samarium diiodide. The application in the synthesis of ureas, amides, sulfonamides, and carbamates is described. The scope of the fluorous N--O linker is exemplified by the synthesis of itopride, a drug used for the treatment of functional dyspepsia. Itopride was synthesized with the aid of fluorous purification methods and the product was isolated in good overall yield, with high purity.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Changing Lanes from Concerted to Stepwise Hydrogenation: The Reduction Mechanism of Frustrated Lewis Acid-Base Pair Trapped CO(2) to Methanol by Ammonia-Borane

Authors: Roy, L; Zimmerman, PM; Paul, A (In Press) Chemistry: A European Journal. HERO ID: 990264


The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

High rate, high-yield production of methanol by ammonia oxidizing bacteria

Authors: Taher, E; Chandran, K (In Press) HERO ID: 1510714

[Less] The overall goal of this study was to develop an appropriate biological process for achieving autotrophic . . . [More] The overall goal of this study was to develop an appropriate biological process for achieving autotrophic conversion of methane (CH4) to methanol (CH3OH). In this study, we employed ammonia oxidizing bacteria (AOB) to selectively and partially oxidize CH4 to CH3OH. In fed-batch reactors using mixed nitrifying enrichment cultures from a continuous bioreactor, up to 59.89 ± 1.12 mg COD/L of CH3OH was produced within an incubation time of 7 h, which is approximately ten times the yield obtained previously using pure cultures of Nitrosomonas europaea. The maximum specific rate of CH4 to CH3OH conversion obtained during this study was 0.82 mg CH3OH COD/mg AOB biomass COD-d, which is 1.5 times the highest value reported with pure cultures. Notwithstanding these positive results, CH4 oxidation to CH3OH by AOB was inhibited by NH3 (the primary substrate for the oxidative enzyme, ammonia monooxygenase, AMO) as well as the product, CH3OH, itself. Further, oxidation of CH4 to CH3OH by AOB was also limited by reducing equivalents supply, which could be overcome by externally supplying hydroxylamine (NH2OH) as an electron donor. Therefore, a potential optimum design for promoting CH4 to CH3OH oxidation by AOB could involve supplying NH3 (needed to maintain AMO activity) uncoupled from the supply of NH2OH and CH4. Partial oxidation of CH4 containing gases to CH3OH by AOB represents an attractive platform for the conversion of a gaseous mixture to an aqueous compound, which could be used as a commodity chemical. Alternately, the nitrate and CH3 OH thus produced could be channeled to a downstream anoxic zone in a biological nitrogen removal process to effect nitrate reduction to N2, using an internally produced organic electron donor.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Shifts between ammonia-oxidizing bacteria and archaea in relation to nitrification potential across trophic gradients in two large Chinese lakes (Lake Taihu and Lake Chaohu)

Authors: Hou, J; Song, C; Cao, X; Zhou, Y (In Press) Water Research. HERO ID: 1510715

[Less] Ammonia oxidation plays a pivotal role in the cycling and removal of nitrogen in aquatic ecosystems. . . . [More] Ammonia oxidation plays a pivotal role in the cycling and removal of nitrogen in aquatic ecosystems. Recent findings have expanded the known ammonia-oxidizing prokaryotes from Bacteria to Archaea. However, the relative importance of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) in nitrification is still debated. Here we showed that, in two large eutrophic lakes in China (Lake Taihu and Lake Chaohu), the abundance of AOA and AOB varied in opposite patterns according to the trophic state, although both AOA and AOB were abundant. In detail, from mesotrophic to eutrophic sites, the AOA abundance decreased, while the AOB increased in abundance and outnumbered the AOA at hypertrophic sites. In parallel, the nitrification rate increased along these trophic gradients and was significantly correlated with both the AOB abundance and the numerical ratio of AOB to AOA. Phylogenetic analysis of bacterial amoA sequences showed that Nitrosomonas oligotropha- and Nitrosospira-affiliated AOB dominated in both lakes, while Nitrosomonas communis-related AOB were only detected at the eutrophic sites. The diversity of AOB increased from mesotrophic to eutrophic sites and was positively correlated with the nitrification rate. Overall, this study enhances our understanding of the ecology of ammonia-oxidizing prokaryotes by elucidating conditions that AOB may numerically predominated over AOA, and indicated that AOA may play a less important role than AOB in the nitrification process of eutrophic lakes.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Nitrogen cycling and relationships between ammonia oxidizers and denitrifiers in a clay-loam soil

Authors: Paranychianakis, NV; Tsiknia, M; Giannakis, G; Nikolaidis, NP; Kalogerakis, N (In Press) Applied Microbiology and Biotechnology. HERO ID: 1510724

[Less] This study investigated the effect of municipal solid waste (MSW) compost (0, 50, and 100 t/ha) on N . . . [More] This study investigated the effect of municipal solid waste (MSW) compost (0, 50, and 100 t/ha) on N cycling and the microorganisms involved in it, in a clay-loam soil. After a release of nitrates (NO(3) (-)-N) in the first 6 days after compost incorporation, soil NO(3) (-)-N content remained constant in all the treatments until day 62, suggesting N immobilization induced by the soil used in this study. Then, soil NO(3) (-)-N content increased in all treatments and especially in the highest compost dose, providing evidence that immobilization effect has been at least partially relieved. amoA gene copies of ammonia-oxidizing archaea (AOA) and bacteria (AOB) followed the overall pattern of soil NO(3) (-)-N content; however, no differences were found in amoA gene copies among treatments, except in the last sampling, an effect attributed to the slight differences in the potential nitrification rate among them. Ammonia oxidizer pattern provided evidence that both groups were involved in ammonia oxidation and changes in their abundance can be used as 'indicator' to predict changes in soil nitrification status. Moreover, the strong correlation between AOA and AOB amoA copies (R (2) = 0.94) and the high slope (13) of the curve suggest that AOA had probably an important role on ammonia oxidation. Denitrifying genes (nirS, nirK, nosZ) also followed the general pattern of soil NO(3) (-)-N, and they were strongly correlated with both groups of ammonia oxidizers, and particularly AOA, suggesting strong interrelationships among them. Losses of N through denitrification, as they were estimated by total nitrogen, were inversely related to soil NO(3) (-)-N content. Similar to ammonia oxidizers, denitrifying gene copies did not differ among compost treatments an effect that could be probably explained by the low availability of organic-C in the MSW compost and hence the competition with aerobic heterotrophs.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Enhanced heme protein expression by ammonia-oxidizing communities acclimated to low dissolved oxygen conditions

Authors: Arnaldos, M; Kunkel, SA; Stark, BC; Pagilla, KR (In Press) Applied Microbiology and Biotechnology. HERO ID: 1510725

[Less] This study has investigated the acclimation of ammonia-oxidizing communities (AOC) to low dissolved . . . [More] This study has investigated the acclimation of ammonia-oxidizing communities (AOC) to low dissolved oxygen (DO) concentrations. Under controlled laboratory conditions, two sequencing batch reactors seeded with activated sludge from the same source were operated at high DO (near saturation) and low DO (0.1 mg O(2)/L) concentrations for a period of 220 days. The results demonstrated stable and complete nitrification at low DO conditions after an acclimation period of approximately 140 days. Acclimation brought about increased specific oxygen uptake rates and enhanced expression of a particular heme protein in the soluble fraction of the cells in the low DO reactor as compared to the high DO reactor. The induced protein was determined not to be any of the enzymes or electron carriers present in the conventional account of ammonia oxidation in ammonia-oxidizing bacteria (AOB). Further research is required to determine the specific nature of the heme protein detected; a preliminary assessment suggests either a type of hemoglobin protein or a lesser-known component of the energy-transducing pathways of AOB. The effect of DO on AOC dynamics was evaluated using the 16S rRNA gene as the basis for phylogenetic comparisons and organism quantification. Ammonium consumption by ammonia-oxidizing archaea and anaerobic ammonia-oxidizing bacteria was ruled out by fluorescent in situ hybridization in both reactors. Even though Nitrosomonas europaea was the dominant AOB lineage in both high and low DO sequencing batch reactors at the end of operation, this enrichment could not be linked in the low DO reactor to acclimation to oxygen-limited conditions.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Composting toilets a misnomer: Excessive ammonia from urine inhibits microbial activity yet is insufficient in sanitizing the end-product

Authors: Hill, GB; Baldwin, SA; Vinnerås, B (In Press) Journal of Environmental Management. HERO ID: 1510728

[Less] End-product from 16 public mixed latrine style composting toilets (CTs) at 12 sites between 50 and 2100 m.a.s.l. . . . [More] End-product from 16 public mixed latrine style composting toilets (CTs) at 12 sites between 50 and 2100 m.a.s.l. in Western North America was tested in order to evaluate the effect of composting variables (TS%, NH(3)-N, temperature, and material age) on compost quality and hygiene (VS%, Escherichia coli, [Formula: see text] -N, and pH). Principal component analysis indicated that TS%, temperature, and material age equally contributed to reduction in VS%. NH(3)-N had the greatest effect on [Formula: see text] -N, E. coli, and pH. Nitrification was significantly inhibited above 386 mg/kg NH(3)-N, but no such limit was found for E. coli, despite a significant (p = 0.016) but weak (r(2) = 0.11) negative relationship. It may be possible to amplify the sanitizing effect of ammonia and overcome pathogen resistance due to low temperatures and re-contamination (caused by poor design) with generous dosing of urea and ash. However, even sanitized, the fertilization effect of discharged material on the natural environment may not be desired or permitted in parks or protected areas where many CTs were found. To this end, operators of CTs need to evaluate their primary management objectives and ensure congruency with proven system capabilities.