SEARCH · PubMed Health

Results for “Autotrophic Processes”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources

PubMed2004

ANAMMOX and partial denitritation in anaerobic nitrogen removal from piggery waste.

The anaerobic ammonium removal from a piggery waste with high strength (56 g COD/L and 5 g T-N/L) was investigated using a lab-scale upflow anaerobic sludge bed reactor at a mesophilic condition. Based on the nitrogen and carbon balance in the process, the contribution of autotrophic and heterotrophic organisms was also evaluated in terms of the influent NO2-N/NH4-N ratio (1:0.8 and 1:1.2 for Phase 1 and Phase 2, respectively). The result of this research demonstrates that the anaerobic ammonium removal from the piggery waste, using the UASB reactor, can be performed successfully. Furthermore, it appears that by using granular sludge as the seed biomass, the ANAMMOX reaction can start more quickly. Average nitrogen conversion was 0.59 kg T-N/m3 reactor-day (0.06 kg T-N/kg VSS/day) and 0.66 kg T-N/m3 reactor-day (0.08 kg T-N/kg VSS/day) for Phase 1 and Phase 2. The NO2-N/NH4-N removal ratio by the ANAMMOX was 1.48 and 1.79 for Phase 1 and Phase 2. The higher nitrite contents (about 50%) in the substrate resulted in higher nitrite nitrogen removal by the partial denitritation, as well as the ANAMMOX reaction, implying higher potential of partial denitritation. However, the result reveals that the ANAMMOX reaction was influenced less by the degree of partial denitritation, and the ANAMMOX bacteria did not compete with denitritation bacteria. The colour of the biomass at the bottom of the reactor changed from dark gray to dark red, which was accompanied by an increase in cytochrome content. At the end of the experiment, red-coloured granular sludge with diameter of 1-2 mm at the lower part of the reactor was also observed.

Animals↗

PubMed1977

[Influence of N-serve on mineral nitrogen forms and microorganisms of the soil (author's transl)].

In a model experiment with soil, 2 stages of nitrogen (without additional N and with 200 kg N/ha in the form of ammonia) and 3 N-Serve stages (without inhibitor and with 0.25 per cent and 1 per cent of inhibitor, relative to 200 kg of N/ha) were followed up over a period of 3 and 6 weeks, respectively, with respect to the dynamics of the nitrification process, the saprophytic soil microorganisms, and the autotrophic nitrifiers. In a second experiment, the ammonia form of nitrogen was substituted by the nitrate and nitrite form, respectively. No serious influence on the heterotrophic soil micro-organisms could be detected in any experimental variant; N-Serve was slightly stimulating, the autotrophic nitrifiers were noticeably depressed by N-Serve. The nitrification process could clearly be proved after 3 weeks already; by N-Serve it was remarkably delayed. Nitrite that had been added to the soil was scarcely transformed into nitrate, whereas it was somewhat more ammonified. The high loss of nitrogen in the nitrite variant cannot be caused by denitrification alone. When nitrate was used, the nitrification was not delayed.

Ammonia↗

PubMed2004

Modeling and simulation of oxygen-limited partial nitritation in a membrane-assisted bioreactor (MBR).

Combination of a partial nitritation process and an anaerobic ammonium oxidation process for the treatment of sludge reject water has some general cost-efficient advantages compared to nitrification-denitrification. The integrated process features two-stage autotrophic conversion of ammonium via nitrite to dinitrogen gas with lower demand for oxygen and no external carbon requirement. A nitrifying membrane-assisted bioreactor (MBR) for the treatment of sludge reject water was operated under continuous aeration at low dissolved oxygen (DO) concentrations with the purpose of generating nitrite accumulation. Microfiltration was applied to allow a high sludge retention time (SRT), resulting in a stable partial nitritation process. During start-up of the MBR, oxygen-limited conditions were induced by increasing the ammonium loading rate and decreasing the oxygen transfer. At a loading rate of 0.9 kg N m(-3) d(-1) and an oxygen concentration below 0.1 mg DO L(-1), conversion to nitrite was close to 50% of the incoming ammonium, thereby yielding an optimal effluent within the stoichiometric requirements for subsequent anaerobic ammonium oxidation. A mathematical model for ammonium oxidation to nitrite and nitrite oxidation to nitrate was developed to describe the oxygen-limited partial nitritation process within the MBR. The model was calibrated with in situ determinations of kinetic parameters for microbial growth, reflecting the intrinsic characteristics of the ammonium oxidizing growth system at limited oxygen availability and high sludge age. The oxygen transfer coefficient (K(L)a) and the ammonium-loading rate were shown to be the appropriate operational variables to describe the experimental data accurately. The validated model was used for further steady state simulation under different operational conditions of hydraulic retention time (HRT), K(L)a, temperature and SRT, with the intention to support optimized process design. Simulation results indicated that stable nitrite production from sludge reject water was feasible with this process even at a relatively low temperature of 20 degrees C with HRT down to 0.25 days.

Bacteria, Anaerobic↗

PubMed2002

Model-based evaluation of temperature and inflow variations on a partial nitrification-ANAMMOX biofilm process.

A mathematical model describing nitrification (nitritification plus nitratification) and anaerobic ammonium oxidation (ANAMMOX) combined in a biofilm reactor was developed. Based on this model, a previously proposed one-reactor completely autotrophic ammonium removal over nitrite (CANON) process was evaluated for its temperature dependency and behaviour under variable inflow. The temperature-dependency of growth rates of the involved organisms is described by an Arrhenius-type equation. If temperature decreases, the activities of the involved organisms decrease. This means that thicker biofilms are needed or the ammonium surface load (ASL) to the biofilm should be decreased to maintain full N-removal at lower temperatures. Although the growth rate of nitrite oxidisers is higher than that of ammonium oxidisers at lower temperatures, these organisms can be effectively competed out due to a lower oxygen affinity. Variable inflow or dissolved oxygen (DO) concentration negatively affect the N-removal efficiency due to an unbalance between applied ASL load and required oxygen concentration. A variation of the dissolved oxygen concentration in a small range (+/- 0.2g O2/m3) has no significant influence on the process performance, which means that requirements on electrode sensitivity and a DO control scheme are not too stringent. A variable ASL has obvious influence on the process performance, at both constant and variable DO. A good adjustment of DO in accordance with the variable ASL is needed to optimise the N-removal efficiency. At T = 20 degrees C, an N-removal efficiency of 88% is possible at ASL = 0.5 g NH4+ - N/mr2 d, in a biofilm of at least 0.7 mm thickness and a DO level of 0.3 g O2/m3 in the bulk liquid.

Biofilms↗

PubMed1997

Health impacts of large releases of radionuclides. Roles of micro-organisms in the environmental fate of radionuclides.

Micro-organisms play important roles in the environmental fate of radionuclides in both aquatic and terrestrial ecosystems, with a multiplicity of physico-chemical and biological mechanisms effecting changes in mobility and speciation. Physico-chemical mechanisms of removal, which may be encompassed by the general term 'biosorption', include adsorption, ion exchange and entrapment. These are features of living and dead organisms as well as their derived products. In living cells biosorptive processes can be directly and indirectly influenced by metabolism, and may be reversible and affected by changing environmental conditions. Metabolism-dependent mechanisms of radionuclide immobilization include metal precipitation as sulfides, sequestration by metal-binding proteins and peptides, and transport and intracellular compartmentation. Chemical transformations of radionuclide species, particularly by reduction, can result in immobilization. Microbial processes involved in solubilization include autotrophic and heterotrophic leaching, complexation by siderophores and other metabolites, and chemical transformations. Such mechanisms are important components of natural biogeochemical cycles for radionuclides and should be considered in any analyses of environmental radionuclide contamination. Several micro-organism-based biotechnologies, e.g. those based on biosorption or precipitation, are of potential use for the treatment of radionuclide contamination.

Adsorption↗

PubMed1990

Evolution of the first metabolic cycles.

There are two alternatives concerning the origin of life: the origin may be heterotrophic or autotrophic. The central problem within the theory of an autotrophic origin is the first process of carbon fixation. I here propose the hypothesis that this process is an autocatalytic cycle that can be retrodictively constructed from the extant reductive citric acid cycle by replacing thioesters by thioacids and by assuming that the required reducing power is obtained from the oxidative formation of pyrite (FeS2). This archaic cycle is strictly chemoautotrophic: photoautotrophy is not required. The cycle is catalytic for pyrite formation and autocatalytic for its own multiplication. It is a consequence of this hypothesis that the postulated cycle cannot exist as a single isolated cycle but must be a member of a network of concatenated homologous cycles, from which all anabolic pathways appear to have sprung.

Biological Evolution↗

PubMed2007

Autotrophic CO2 fixation via the reductive tricarboxylic acid cycle in different lineages within the phylum Aquificae: evidence for two ways of citrate cleavage.

Autotrophic carbon fixation was characterized in representative members of the three lineages of the bacterial phylum Aquificae. Enzyme activity measurements and the detection of key genes demonstrated that Aquificae use the reductive tricarboxylic acid (TCA) cycle for autotrophic CO(2) fixation. This is the first time that strains of the Hydrogenothermaceae and 'Desulfurobacteriaceae' have been investigated for enzymes of autotrophic carbon fixation. Unexpectedly, two different mechanisms of citrate cleavage could be identified within the Aquificae. Aquificaceae use citryl-CoA synthetase and citryl-CoA lyase, whereas Hydrogenothermaceae and 'Desulfurobacteriaceae' use ATP citrate lyase. The first mechanism is likely to represent the ancestral version of the reductive TCA cycle. Sequence analyses further suggest that ATP citrate lyase formed by a gene fusion of citryl-CoA synthetase and citryl-CoA lyase and subsequently became involved in a modified version of this pathway. However, rather than having evolved within the Aquificae, our phylogenetic analyses indicate that Aquificae obtained their ATP citrate lyase through lateral gene transfer. Aquificae play an important role in biogeochemical processes in a variety of high-temperature habitats. Thus, these findings substantiate the hypothesis that autotrophic carbon fixation through the reductive TCA cycle is widespread and contributes significantly to biomass production particularly in hydrothermal habitats.

ATP Citrate (pro-S)-Lyase↗

PubMed2003

[Oxygen-limited autotrophic nitrification and denitrification--a novel technology for biological nitrogen removal].

Oxygen-limited autotrophic nitrification and denitrification (OLAND) is a biological nitrogen removal process coupled with partial nitrification and anaerobic ammonium oxidation. In our study, the nitrification was blocked at nitrite stage by controlling the dissolved oxygen concentration at 0.1-0.3 mg.L-1, and then, the denitrification proceeded, with the residual ammonium at the partial nitrification stage as electron donor. As a completely autotrophic nitrification-denitrification process, the OLAND was of many advantages (e.g., low energy consumption, high nitrogen removal rate and small footprint of system), and suitable in particular for treating low COD/NH4(+)-N ratio wastewater. It has become one of the most prosperous and practicable biological nitrogen removal technologies. The recent research of OLAND was reviewed, and its microbial mechanism as well as its applicable prospect was remarked in this paper.

Ammonia↗

PubMed2001

State estimation for a biological phosphorus removal process using an asymptotic observer.

This study investigated the use of an asymptotic observer for state estimation in a continuous biological phosphorus removal process. The estimated states are the concentration of heterotrophic, autotrophic and phosphorus accumulating organisms, polyphosphate, glycogen and PHA. The reaction scheme describing the process was simplified from a combined ASM 1-Delft model. Three examples were investigated: operation at steady state, operation at steady state with a random white-noise in the measurements and operation with a ramp disturbance. In each case, the estimation was quite accurate even if the convergence, driven by the dilution rate, was slow (from 15 to 60 days). The propagation of the measurement noise and a bias in the estimation of glycogen and PHA could be the result of the high condition number of one of the matrices used in the algorithm of the asymptotic observer for the aerated tanks.

Air↗

PubMed2005

Kinetics, diffusional limitation and microscale distribution of chemistry and organisms in a CANON reactor.

In the Completely Autotrophic Nitrogen removal Over Nitrite (CANON) process, aerobic and anaerobic ammonia oxidizing bacteria cooperate to remove ammonia in one oxygen-limited reactor. Kinetic studies, microsensor analysis, and fluorescence in situ hybridization on CANON biomass showed a partial differentiation of processes and organisms within and among aggregates. Under normal oxygen-limited conditions ( approximately 5 microM O2), aerobic ammonia oxidation (nitrification) was restricted to an outer shell (<100 microm) while anaerobic ammonia oxidation (anammox) was found in the central anoxic parts. Larger type aggregates (>500 microm) accounted for 68% of the anammox potential whereas 65% of the nitrification potential was found in the smaller aggregates (<500 microm). Analysis with O2 and NO2- microsensors showed that the thickness of the activity zones varied as a function of bulk O2 and NO2- concentrations and flow rate.

Aerobiosis↗

PubMed1996

Influence of microorganisms on the environmental fate of radionuclides.

Microorganisms have a significant influence on the environmental fate of radionuclides in aquatic and terrestrial ecosystems with a multiplicity of physico-chemical and biological mechanisms effecting changes in mobility and speciation. Physico-chemical mechanisms of removal include association with extracellular materials, metabolites and cell walls which are features of living and dead organisms. In living cells, some physico-chemical processes are reversible, influenced by metabolism and changing environmental conditions. Metabolism-dependent mechanisms of radionuclide immobilization include sulphide precipitation, transport and intracellular compartmentation and/or sequestration by proteins and peptides. In addition, chemical reduction to less soluble forms can result in immobilization. Microbial processes involved in radionuclide solubilization include autotrophic and heterotrophic leaching, and complexation by siderophores and other metabolites. Such mechanisms are important components of biogeochemical cycles for radionuclides and should be considered in any analyses of environmental radionuclide contamination. In addition, several microorganism-based biotechnologies are receiving interest as potential treatment methods.

Absorption↗

PubMed2006

Anaerobic arsenite oxidation by novel denitrifying isolates.

Autotrophic microorganisms have been isolated that are able to derive energy from the oxidation of arsenite [As(III)] to arsenate [As(V)] under aerobic conditions. Based on chemical energetics, microbial oxidation of As(III) can occur in the absence of oxygen, and may be relevant in some environments. Enrichment cultures were established from an arsenic contaminated industrial soil amended with As(III) as the electron donor, inorganic C as the carbon source and nitrate as the electron acceptor. In the active enrichment cultures, oxidation of As(III) was stoichiometrically coupled to the reduction of NO(3) (-). Two autotrophic As(III)-oxidizing strains were isolated that completely oxidized 5 mM As(III) within 7 days under denitrifying conditions. Based on 16S rRNA gene sequencing results, strain DAO1 was 99% related to Azoarcus and strain DAO10 was most closely related to a Sinorhizobium. The nitrous oxide reductase (nosZ) and the RuBisCO Type II (cbbM) genes were successfully amplified from both isolates underscoring their ability to denitrify and fix CO(2) while coupled to As(III) oxidation. Although limited work has been done to examine the diversity of anaerobic autotrophic oxidizers of As(III), this process may be an important component in the biological cycling of arsenic within the environment.

Arsenites↗

PubMed2006

Nitrogen removal rates at a technical-scale pilot plant with the one-stage partial nitritation/Anammox process.

Traditional nitrification/denitrification is not suitable for nitrogen removal when wastewater contains high concentrations of ammonium nitrogen and low concentrations of biodegradable carbon. Recently, a deammonification process was developed and proposed as a new technology for treatment of such streams. This process relies on a stable interaction between aerobic bacteria Nitrosomonas, that accomplish partial nitritation and anaerobic bacteria Planctomycetales, which conduct the Anammox reaction. Simultaneous performance of these two processes can lead to a complete autotrophic nitrogen removal in one single reactor. The experiments where nitrogen was removed in one reactor were performed at a technical-scale moving-bed pilot plant, filled with Kaldnes rings and supplied with supernatant after dewatering of digested sludge. It was found that a nitrogen removal rate obtained at the pilot plant was 1.9 g m(-2) d(-1). Parallel to the pilot plant run, a series of batch tests were carried out under anoxic and aerobic conditions. Within the batch tests, where the pilot plant's conditions were simulated, removal rates reached up to 3 g N m(-2)d(-1). Moreover, the batch tests with inhibition of Nitrosomonas showed that only the Anammox bacteria (not anoxic removal by Nitrosomonas) are responsible for nitrogen removal.

Aerobiosis↗

PubMed2005

Enrichment of anammox from activated sludge and its application in the CANON process.

A microbial culture capable of actively oxidizing ammonium to dinitrogen gas in the absence of oxygen, using nitrite as the electron acceptor, was enriched from local activated sludge (Western Australia) in <14 weeks. The maximum anaerobic ammonium oxidation (i.e., anammox) activity achieved by the anaerobic culture was 0.26 mmol NH (4) (+) (g biomass)(-1) h(-1) (0.58 kg total-N m(-3) day(-1)). Qualitative FISH analysis (fluorescence in situ hybridization) confirmed the phylogenetic position of the enriched microorganism as belonging to the order Planctomycetales, in which all currently identified anammox strains fall. Preliminary FISH analysis suggests the anammox strain belongs to the same phylogenetic group as the Candidatus 'Brocadia anammoxidans' strain discovered in the Netherlands. However, there are quite a few differences in the target sites for the more specific probes of these organisms and it is therefore likely to represent a new species of anammox bacteria. A small amount of aerobic ammonium-oxidizing biomass was inoculated into the anammox reactor (10% v/v) to initiate completely autotrophic nitrogen removal over nitrite (the CANON process) in chemostat culture. The culture was always under oxygen limitation and no organic carbon was added. The CANON reactor was operated as an intermittently aerated system with 20 min aerobiosis and 30 min anaerobiosis, during which aerobic and anaerobic ammonium oxidation were performed in sequential fashion, respectively. Anammox was not inhibited by repeated intermittent exposure to oxygen, allowing sustained, completely autotrophic ammonium removal (0.08 kg N m(-3) day(-1)) for an extended period of time.

Aerobiosis↗

PubMed2003

The role of inorganic carbon limitation in biological nitrogen removal of extremely ammonia concentrated wastewater.

It is clear from the fundamental biochemical processes that nitrification of extremely concentrated ammonia loads requires-among others-(1) sufficient alkalinity to buffer acidification and (2) bicarbonate as the substrate for the autotrophic biomass. However, at low pH values the aeration process causes CO(2) stripping and consequently a decrease of the available inorganic carbon. In order to analyse such complex interactions, we suggest in this paper an enhanced version of the widely acknowledged IWA (formerly IAWQ) activated sludge models. These model enlargements comprise an ion-balance for the calculation of the pH value and of dissociation species, a balance of inorganic carbon and a more detailed description of the relevant N-elimination processes and their inhibitions. The model was successfully employed to optimise a treatment strategy for rejection-water and landfill leachate (500-2000 mg ammonia-Nl(-1), COD/N ratio of 0.25-4). Detailed data from two full-scale rejection-water treatment plants were used for systems identification, model calibration and validation. The results suggest that inhibition and limitation by nitrous acid (HNO(2)) and unionised ammonia (NH(3)) have often been overestimated. In this investigation the bicarbonate concentration proved to be crucial for the process. The optimisation of the bicarbonate concentration in the reactor could improve the nitrozation rate up to 100mg NH(4)(+)-Nl(-1)h(-1).

Ammonia↗

PubMed2001

Estimating biomass yield coefficients for autotrophic ammonia and nitrite oxidation from batch respirograms.

Kinetic characterization of biological processes via batch respirometry requires an accurate estimate of the biomass yield coefficient because it provides the stoichiometric link between biomass synthesis, substrate consumption and oxygen uptake. Expressions for biomass yield coefficients describing autotrophic ammonia and nitrite oxidation were derived from a mechanistically based electron balanced equation. We demonstrate that applying the conventional expression used to calculate the heterotrophic biomass yield results in erroneous estimates for the autotrophic biomass yield. Yield coefficients for autotrophic NH4(+)-N to NO2(-)-N oxidation and NH4(+)-N to NO3(-)-N oxidation were overestimated by 27 to 36%. Due to correlation between the maximum specific growth rate and the biomass yield, the error in yield values propagated in 30 to 40% overestimates of the maximum specific growth rate coefficient for NH4(+)-N oxidation determined from batch respirograms. Therefore, it is essential to employ the correct expression to estimate the autotrophic biomass yield coefficient from batch respirograms due its inadvertent impact on subsequent parameter estimation.

Ammonia↗

PubMed1994

Formation of amide bonds without a condensation agent and implications for origin of life.

Amide bonds are of central importance for biochemistry; in the guise of peptide bonds, they form the backbone of proteins. The formation of amide bonds without the assistance of enzymes poses a major challenge for theories of the origin of life. Enzyme-free formation of amide bonds between amino acids has been demonstrated in the presence of condensing agents such as cyanamide. Here we report the formation of amide bonds in aqueous solution in the absence of any condensing agent. We find that the formation of pyrite (FeS2) from FeS and H2S can provide the driving force for reductive acetylation of amino acids with mercaptoacetic acid (HSCH2COOH). The redox energy of pyrite formation permits the activation of the carboxylic acid group, which is converted to a species that reacts readily with amines. This process provides support for the chemo-autotrophic theory for the origin of life, in which pyrite formation supplies the energy source for the first autocatalytic reproduction cycle.

Acetylation↗

PubMed1983

Chromosome transfer and R-prime plasmid formation mediated by plasmid pULB113 (RP4::mini-Mu) in Alcaligenes eutrophus CH34 and Pseudomonas fluorescens 6.2.

Plasmid pULB113 (RP4::mini-Mu), which contains the mini-Mu transposon, promoted both homologous and heterologous gene transfer from Pseudomonas fluorescens 6.2 and Alcaligenes eutrophus CH34. Homologous gene transfer in P. fluorescens 6.2 and A. eutrophus CH34 occurred at a frequency of 10(-4) to 10(-5), and recombinants inherited unselected recessive markers, suggesting a process of chromosome mobilization. Loci involved in autotrophic growth were among those transferred in A. eutrophus. In heterospecific matings, markers were transferred from P. fluorescens to A. eutrophus, Salmonella typhimurium LT2, and Escherichia coli, from A. eutrophus to P. fluorescens, and from Erwinia carotovora subsp. chrysanthemi to A. eutrophus. Heterospecific matings resulted in the formation of R-prime plasmids at frequencies of 10(-7) to 10(-4) per transferred plasmid. When S. typhimurium was the recipient, we observed R-prime plasmids with both restriction-proficient and restriction-deficient strains, although restriction markedly affected the frequency of transfer of pULB113. R-prime plasmids were quite stable, but lost the transposed marker more easily in a rec+ background than in a recA background, suggesting excision of transposed material by reciprocal recombination between flanking copies of mini-Mu. R-prime plasmids could be transferred easily into different recipients and were used in complementation studies. PstI restriction digests of four R-prime plasmids carrying P. fluorescens 6.2 DNA showed a number of additional bands, suggesting that several genes were transposed together with the selected marker on the plasmid.

Alcaligenes↗