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651.
Abstract Membranes from Nitrosomonas europaea were found to contain two b -type cytochromes. One had an α-band centred at 562 nm and E m,7 =+ 155 mV; the other had an α-band maximum close to 558 nm and E m,7 =+ 40 mV. A b -type cytochrome ran at an apparent M r of 32000 on lithium dodecyl sulphate/polyacrylamide gels at 4°C. 相似文献
652.
Tonči Rezić Božidar Šantek Srđan Novak Vladimir Marić 《World journal of microbiology & biotechnology》2007,23(7):987-996
In this work, the heterotrophic cultivation of bacterium Paracoccus denitrificans has been studied in a horizontal rotating tubular bioreactor (HRTB). After development of a microbial biofilm on the inner
surface of the HRTB, conditions for one-step removal of acetate and ammonium ion were created. The effect of bioreactor process
parameters [medium inflow rate (F) and bioreactor rotation speed (n)] on the bioprocess dynamics in the HRTB was studied. Nitrite and nitrogen oxides (NO and N2O) were detected as intermediates of ammonium ion degradation. The biofilm thickness and the nitrite concentration were gradually
reduced with increase of bioreactor rotation speed when the medium inflow rate was in the range of 0.5–1.5 l h−1. Further increase of inflow rate (2.0–2.5 l h−1) did not have a significant effect on the biofilm thickness and nitrite concentration along the HRTB. Complete acetate consumption
was observed when the inflow rate was in the range of 0.5–1.5 l h−1 at all bioreactor rotation speeds. Significant pH gradient (cca 1 pH unit) along the HRTB was only observed at the highest
inflow rate (2.5 l h−1). The results have clearly shown that acetate and ammonium ion removal by P. denitificans can be successfully conducted in a HRTB as a one-step process. 相似文献
653.
654.
Ability of nitrapyrin,dicyandiamide and acetylene to retard nitrification in a mineral and an organic soil 总被引:1,自引:0,他引:1
Laboratory experiments were conducted to evaluate the efficacy of nitrapyrin, dicyandiamide (DCD) and acetylene (C2H2) as nitrification inhibitors in a silt loam and oragnic soil with and without added NH4. Nitrapyrin (8 μg/g soil) and DCD (20 μg/g soil) were very effective in retarding nitrification of NH4−N in the silt loam soil during 14 days of aerobic incubation at 30°C. However neither nitrapyrin, (20 μg/g soil) nor DCD
(20 or 100 μg/g soil) were effective in retarding NO3 production in the organic soil not amended with NH4. Dicyandiamide was moderately effective in retarding nitrification (39% inhibition) at 100 μg/g concentration but nitrapyrin
at 20 μg/g rate had little effect (8% inhibition) on nitrification in the organic soil amended with NH4. In a separate experiment C2H2 was a very effective inhibitor in both soils when present in the flask atmosphere at 0.1% or 1% (v/v). 相似文献
655.
The coupled system of partial nitrification and anaerobic ammonium oxidation (Anammox) is efficient in nitrogen removal from wastewater. In this study, the effect of different oxygen concentrations on partial nitrification performance with a sequencing batch reactor (SBR) was investigated. Results indicate that, partial nitrification of landfill leachate could be successfully achieved under the 1.0–2.0 mg L−1 dissolved oxygen (DO) condition after 118 d long-term operation, and that the effluent is suitable for an Anammox reactor. Further decreasing or increasing the DO concentration, however, would lead to a decay of nitrification performance. Additionally, the MLSS concentration in the reactor increased with increasing DO concentration. Respirometric assays suggest that low DO conditions (<2 mg L−1) favor the ammonia-oxidizing bacteria (AOB) and significantly inhibit nitrite oxidizing bacteria (NOB) and aerobic heterotrophic bacteria (AHB); whereas high DO conditions (>3 mg L−1) allow AHB to dominate and significantly inhibit AOB. Therefore, the optimal condition for partial nitrification of landfill leachate is 1.0–2.0 mg L−1 DO concentration. 相似文献
656.
The bioenergetic basis for the decrease in metabolic diversity at increasing salt concentrations: implications for the functioning of salt lake ecosystems 总被引:11,自引:1,他引:10
Aharon Oren 《Hydrobiologia》2001,466(1-3):61-72
Examination of the microbial diversity in hypersaline lakes of increasing salt concentrations shows that certain types of dissimilatory metabolism do not occur at the highest salinities. Examples are methanogenesis from hydrogen and carbon dioxide or from acetate, dissimilatory sulfate reduction with oxidation of acetate, and autotrophic nitrification. The observations can be explained on the basis of the energetic cost of haloadaptation used by the different metabolic groups and the free-energy change associated with the dissimilatory reactions. All halophilic microorganisms spend large amounts of energy to maintain steep gradients of Na+ and K+concentrations across their cytoplasmic membrane. Most Bacteria and also the methanogenic Archaea produce high intracellular concentrations of organic osmotic solutes at a high energetic cost. The halophilic aerobic Archaea (order Halobacteriales) and the halophilic fermentative Bacteria (order Halanaerobiales) use KCl as the main intracellular solute. This strategy, while requiring far-reaching adaptations of the intracellular machinery, is energetically more favorable than production of organic compatible solutes. By combining information on the amount of energy available to each physiological group and the strategy used to cope with salt stress, a coherent model emerges that provides explanations for the upper salinity limit at which the different microbial conversions occur in hypersaline lakes. 相似文献
657.
Topsoil stockpiled for 4 years resulted in an accumulation of NH4-N at depths of 1m or more in mound, as measured by an ammonia gas-sensing electrode. When leached with water these soils were also found to contain high concentrations of dissolved organic C below 1m. Both NH4-N and DOC were products of microbial mineralisation of soil organic matter that accumulated under anaerobic conditions. When these soils were restored a flush of decomposition took place, fuelled by labile organic matter and soluble nitrogen.Stockpiled soil which underwent an ammonium-rich perfusion regime in the laboratory indicated that in-mound soils rapidly attained greater nitrification potential than surface mound soils and also had greater potential for further mineralisation of organic matter to NH4-N. This further production was seen as a contribution from the bacterial flush, stimulated by the large labile-C pool already present.As the bulk of stored soil was anaerobic, restored soils were seen as potentially wasteful of their N-reserves; the fate of nitrogen and soluble carbon compounds in restored soils is discussed. 相似文献
658.
Oxygen depletion of lake and seawater is a serious condition with large implications for biodiversity. Therefore, in LCA,
the potential oxygen demand of water emissions is estimated under the label eutrophication impact category. This impact category
should contain the impact of water emissions on the total oxygen consumption in the receiving water. This means that it should
include both primary and secondary oxygen consumption. In spite of this, the oxygen needed to oxidise ammonia has normally
not been taken into account when quantifying the eutrophication impact category.
In this paper, weighting factors for ammonium/ammonia are suggested for the eutrophication impact category. It is shown that,
for treated wastewater, the amount of oxygen needed for nitrification of ammonia is important when compared to the potential
eutrophication calculated using the current recommended weighting factors. These weighting factors take into account oxygen
needed to oxidise the organic matter in the wastewater emission and that needed to degrade the algae potentially grown due
to the emission of nutrients. 相似文献