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1.
Water Res ; 182: 115896, 2020 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-32830101

RESUMO

Current H2S treatment methods for sour gases require considerable amounts of chemicals and energy, or in case of biological treatment, unwanted diluents such as oxygen or nitrogen may be introduced. In order to reduce those requirements, the viability of an anaerobic biological H2S removal process using purple phototrophic bacteria (PPB) was investigated in this study. PPB can use sunlight, and centrate as nutrient source, thus potentially reducing energy and chemical requirements. An added benefit is the production of biomass with potential uses, such as single cell protein. An inoculum of PPB enriched from domestic wastewater was grown photoautotrophically with sulfide as the electron donor and inorganic carbon in a mixed culture. Additionally, synthetic medium and centrate as well as high (56 ±â€¯11 Wm-2) and low (27 ±â€¯3 Wm-2) IR irradiation were trialled. Finally, a process model was developed to study biomass specific removal rates and yield. The results showed that a mixed culture of PPB removed sulfide completely in synthetic media (121 ±â€¯9 mg-S.L-1) at a maximum rate of 1.79 ±â€¯0.16 mg-S(Lh)-1 (low irradiance) and 2.9 mg-S(Lh)-1 (high irradiance). The pH increased in both experiments from about 8.5 to 9. Sulfide removal rates using centrate and low irradiance were similar. However Fe and Mn were found to be limiting growth and sulfide removal. In all experiments, Chromatiaceae (purple sulfur bacteria) were most abundant at the end of the experiment, while at the start purple non-sulfur bacteria were most abundant (from the inoculum). Process modelling and experimental work identified the sulfide oxidation to be a multi-step process with accumulation of intermediates. Specific rates were directly dependent on light input, doubling at high irradiance. Sulfide oxidation was estimated at 0.100 ±â€¯0.014 h-1 (0.085 ±â€¯0.012 g-S(g-VS.h)-1) at low irradiance, and the biomass yield at 0.86 ±â€¯0.05 mg-COD.mg-COD-1. This process model enables the virtual evaluation of autotrophic sulfide removal by PPB in a continuous scaled-up process. Overall, the photoautotrophic removal of sulfide seems to be a viable option, especially because of the possibility of using sunlight as an energy source and centrate as a nutrient source.


Assuntos
Processos Autotróficos , Reatores Biológicos , Bactérias , Sulfetos , Águas Residuárias
2.
Mar Pollut Bull ; 157: 111261, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32658663

RESUMO

The temporal-spatial distribution of marine autotrophic picoplankton (APP) in the central Bohai Sea was investigated in April (spring), June (early summer), August (summer), and October (autumn) in 2015 through a combination of HPLC-pigment method and flow cytometry. Flow cytometry results showed that APP was composed of Synechococcus (Syn) and pico-eukaryotes (PEUKs). The lowest average abundances of Syn and PEUKs was obtained in April. Afterward, the average APP density substantially increased, and Syn dominated the total cell abundances. Although generally outnumbered by Syn, PEUKs were the larger contributor to total APP carbon biomass (>52%) in all the cruises, except in August, when Syn bloomed. Compared with the cytometric method, HPLC-pigment CHEMTAX revealed a more sophisticated diversity of APP community. In April, diatoms were the main contributor to pico-Chl a, whereas prasinophytes became the main contributor in June and October. Syn bloom was evidenced by CHEMTAX, which revealed that it contributed 69.3% of Chl a in August. Redundancy analysis suggested that temperature was the main factor influencing the distribution of APP. Moreover, nutrients and their structures had some effects, which depended on different APP groups in the area. The accordance between CHEMTAX and cytometric method was evaluated through correlation analysis. A significantly positive correlation between cell abundance and CHEMTAX-derived Chl a was observed for Syn in August and PEUKs in June. Nevertheless, further study is needed owing to the observed discrepancies between the methods.


Assuntos
Processos Autotróficos , Água do Mar , China , Cromatografia Líquida de Alta Pressão , Citometria de Fluxo , Fitoplâncton
3.
Bioresour Technol ; 315: 123826, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32682266

RESUMO

Elemental sulfur (S0) introduction could achieve the co-existence of heterotrophic denitrification (HDN) and autotrophic denitrification (ADN) in practical organic-limited nitrate wastewater treatment. Until now, changes in key functional species, metabolic pathways and microbial products in the succession process of microbialcommunities based on different of pollutant concentration and trophic conditions are still unclear. In present study, high-efficiency of total nitrogen (TN) removal achieved in S0-based ADN bioreactor at influent nitrate of 30-240 mg/L. Content of proteins and polysaccharides in extracellular polymeric substances (EPS) declined with nitrate loads increased. The key functional heterotrophic denitrifiers (Hyphomicrobium, Trichococcus, Rivibacter) and autotrophic biotope (Thiobacillus, Thiomonas, Ferritrophicum, Flavobacterium, Stenotrophomonas, Cloacibacterium and Pseudoxanthomonas) jointly contributed to high nitrogen removal efficiency at different nitrate loads. Furthermore, network analysis verified that symbiotic relationships accounted for the major proportion (88.3%) of the microbial network. The enhanced of nitrogen and sulfur metabolism improved nitrogen removal and S0-based autotrophic denitrification capacity.


Assuntos
Microbiota , Águas Residuárias , Processos Autotróficos , Reatores Biológicos , Desnitrificação , Redes e Vias Metabólicas , Nitratos , Nitrogênio , Enxofre
4.
Water Sci Technol ; 81(5): 1071-1079, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32541123

RESUMO

In this study, the completely autotrophic nitrogen removal over nitrite (CANON) process was initiated in a sequencing batch biofilm reactor (SBBR). Then the reactor was operated under different IC/N ratios. The total inorganic nitrogen removal efficiency (TINRE) at IC/N ratios of 0.75, 1.0, 1.25, 1.5 and 2.0 were 37.0 ± 11.0%, 58.9 ± 10.2%, 73.9 ± 3.2%, 73.6 ± 1.8% and 72.6 ± 2.0%, respectively. The suitable range of IC/N ratio in this research is 1.25-2.0. The poor nitrogen removal performance at IC/N ratio of 0.75 was due to the lack of growth substrate for AnAOB and low pH simultaneously; at IC/N ratio of 1.0 this was because the substrate concentration was insufficient for fully recovering the AnAOB activities. Microbial analysis indicated that Nitrosomonas, Nitrospira and Candidatus Brocadia were the main ammonium oxidation bacteria (AOB), nitrite oxidation bacteria (NOB) and anammox bacteria (AnAOB), respectively. In addition, at IC ratios of 1.25 or higher, denitrification was promoted with the rise of IC/N ratio, which might be because the change of IC concentrations caused cell lysis of microorganisms and provided organic matter for denitrification.


Assuntos
Microbiota , Nitritos , Processos Autotróficos , Biofilmes , Reatores Biológicos , Carbono , Desnitrificação , Nitrogênio
5.
Environ Sci Pollut Res Int ; 27(29): 36816-36825, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32572742

RESUMO

The performance and process of the constructed pyrite-based mixotrophic denitrification (POMD) system using pyrite and residual organic matters as the co-electron donors were investigated for simultaneous removal of N and P from secondary effluent. After the batch experiments, 61.80 ± 3.26% of phosphate and 99.99 ± 0.01% of nitrate were removed, and the obtained nitrate removal rate constant can reach 2.09 days-1 in POMD system, which was significantly superior to that reported (0.95 day-1) in pyrite-based autotrophic denitrification (PAD) system. PO43--P removal was mainly achieved via chemical precipitation as FePO4 with iron, and it was irrelevant with the initial nitrate and ammonium concentrations. High-throughput 16S rRNA gene sequencing analysis showed the coexistence of heterotrophic and autotrophic denitrifiers in the mixotrophic environment. The denitrification process could be divided into two stages according to the carbon balance and calculation of sulfate accumulation: (a) nitrate was mainly reduced heterotrophically during 12-36 h and (b) nitrate was reduced autotrophically after 36 h. The calculated proportion of heterotrophic denitrification was 58.17 ± 3.78%, which was promoted by a higher ammonium concentration. These findings are likely to be useful in understanding the mixotrophic denitrification process and developing a cost-effective technology to simultaneously remove N and P from secondary effluent. Graphical abstract.


Assuntos
Desnitrificação , Fósforo , Processos Autotróficos , Reatores Biológicos , Ferro , Nitratos , RNA Ribossômico 16S , Sulfetos , Enxofre
6.
Chemosphere ; 257: 127272, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32534299

RESUMO

A hybrid biofilter was established on Fe-C supported carriers aimed to enhance nitrogen removal from polluted water of low Carbon/Nitrogen (C/N) ratio. Effects of organic loadings, hydraulic retention time (HRT), additional electron donor (Fe2+) supplementation and operation mode on the performance of the biofilter were investigated. Results showed that up-flow operation mode was better than down-flow mode in terms of nitrate and total nitrogen (TN) removal at low COD/N. The average removal of NO3--N, NH4+ -N and TN attained 83.1%, 84.7% and 81.2%, respectively, under the conditions of influent COD/NO3--N = 1.5-3.6, HRT = 10 h and up-flow operation. When the biofilter was operated under autotrophic conditions without organic compounds in influent as electron donors, the biofilter achieved a NO3--N removal of 46% and TN removal of 56% depending on the innate electron donors provided by the Fe-C carriers. Supplementation of Fe2+ in influent further promoted autotrophic denitrifying process, and the removal of NO3--N and TN increased to 96.3% and 84.7%, respectively, at the mol ratio of Fe2+/NO3- = 10 and HRT = 10 h. The microbial community was analyzed for the biofilm samples enriched under heterotrophic and autotrophic conditions. The Fe-C biofilter boosted the growth of a large population of mixotrophic denitrifying bacteria including Gallionella, heterotrophic denitrifying bacteria Denitratisoma, and autotrophic denitrifying bacteria Thiobacillus and Thioalkalispira. On the whole, the biofilter coupled with Fe-C micro-electrolysis provides a novel strategy to treat polluted water of low C/N under both heterotrophic and autotrophic conditions.


Assuntos
Reatores Biológicos/microbiologia , Nitrogênio/metabolismo , Processos Autotróficos , Bactérias , Carbono , Desnitrificação , Poluentes Ambientais , Processos Heterotróficos , Nitratos , Águas Residuárias , Água
7.
J Ind Microbiol Biotechnol ; 47(4-5): 357-372, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32385605

RESUMO

Yeast and microalgae are microorganisms with widely diverging physiological and biotechnological properties. Accordingly, their fields of applications diverge: yeasts are primarily applied in processes related to fermentation, while microalgae are used for the production of high-value metabolites and green technologies such as carbon capture. Heterotrophic-autotrophic systems and synthetic ecology approaches have been proposed as tools to achieve stable combinations of such evolutionarily unrelated species. We describe an entirely novel synthetic ecology-based approach to evolve co-operative behaviour between winery wastewater isolates of the yeast Saccharomyces cerevisiae and microalga Chlorella sorokiniana. The data show that biomass production and mutualistic growth improved when co-evolved yeast and microalgae strains were paired together. Combinations of co-evolved strains displayed a range of phenotypes, including differences in amino acid profiles. Taken together, the results demonstrate that biotic selection pressures can lead to improved mutualistic growth phenotypes over relatively short time periods.


Assuntos
Chlorella/fisiologia , Saccharomyces cerevisiae/fisiologia , Simbiose , Processos Autotróficos , Biomassa , Fermentação , Processos Heterotróficos , Microalgas/fisiologia
8.
J Environ Manage ; 266: 110586, 2020 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-32392139

RESUMO

Expanded granular sludge bed (EGSB) reactors were rarely applied for complete ammonium removal over nitrite. In this study, a high ammonium loading rate of 3677 mg N/L/d was achieved in an EGSB reactor. Approximately 5.5-8.5% of influent ammonium was converted to nitrous oxide (N2O) that is a potent greenhouse gas. Moreover, the percentage increased linearly with the increase in ammonium load. A model well matched the reactor dynamics. The model indicated that hydroxylamine (NH2OH) oxidation contributed to over 40% of produced N2O, and denitrification by ammonium oxidizing bacteria contributed to N2O emission significantly. Furthermore, the model suggests that a low oxygen concentration can result in a low N2O emission at the cost of a slightly low ammonium removal rate while influent organic matter play a minor role in reducing N2O emission. This study shows that EGSB reactors are effective in ammonium removal. In addition, the emission of N2O is significant.


Assuntos
Desnitrificação , Nitritos , Processos Autotróficos , Reatores Biológicos , Nitrogênio , Óxido Nitroso , Esgotos
9.
Water Res ; 178: 115848, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32361288

RESUMO

Micro-aerobic enhancement technology has been developed as an effective tool to enhance simultaneous removal of sulfide, nitrate and organic carbon during the integrated autotrophic-heterotrophic denitrification (IAHD) process under high loading; however, its mechanism of enhancement for functional bacteria remains ambiguous. In this study, we discovered that heterotrophic sulfide-oxidizing nitrate-reducing bacteria (h-soNRB) are responsible for enhancing IAHD performance under micro-aerobic conditions with high sulfide loading. In a continuous IAHD bioreactor, aeration rate of 2.6 mL min-1·L-1 promoted 2 to 4 times higher removal efficiencies of sulfide, nitrate and acetate with an influent sulfide concentration of 18.75 mmol/L. Metagenomic analysis revealed that trace oxygen stimulated the abundance of genes responsible for sulfide oxidation (sqr, glpE, pdo, sox and cysK), which were upregulated by 15.2%-129.9%, and the genes encoding nitrate reductase were up-regulated by 67.4%. The increased acetate removal efficiency was attributed to upregulation of ack, pta and TCA cycle related genes. The h-NRB Pseudomonas, Azoarcus, Thauera and Halomonas were detected and regarded as h-soNRB in our bioreactor. According to Illumina MiSeq sequencing, these genera were absolutely dominant in the micro-aerobic microbial community at relative abundances ranging from 82.72% to 90.84%. The sulfide, nitrate and acetate removal rates of Pseudomonas C27, a typical h-soNRB, were at least 10 times higher under micro-aerobic conditions than under anaerobic conditions. Besides, the sulfur, nitrogen and carbon metabolic network was constructed based on the Pseudomonas C27 genome. The pdo and cysK genes found in this strain may be the most advantageous for autotrophic sulfide oxidizing nitrate reducing bacteria (a-soNRB), which are closely related to the high-efficiency sulfide, nitrate and acetate removal performance under high sulfide concentrations and a limited oxygen supply. In addition, after micro-aerobic cultivation, the anaerobic sulfide loading tolerance of the IAHD bioreactor increased from 18.75 to 37.5 mmol/L with sulfide, nitrate and acetate removal efficiencies increasing 1.5 to 3 times, which suggests that intermittent micro-aeration might be a more economical and efficient regime for high-sulfide IAHD regulation.


Assuntos
Processos Autotróficos , Desnitrificação , Bactérias , Reatores Biológicos , Nitratos , Oxirredução , Sulfetos
10.
Bioresour Technol ; 310: 123465, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32388206

RESUMO

Nitrogen removal from saline wastewater is challenging due to adverse effects of salinity on biological processes. A novel sulfur-autotrophic cyclic denitrification filter (CDF) was tested for marine recirculating aquaculture systems (RAS) under varying conditions. Low ammonia, nitrite and sulfide concentrations were maintained at residence times between 4 and 12 h. After introduction of Poecilia sphenops, concentrations of NH4+-N, NO2--N, NO3--N were maintained below 1, 1, and 60 mg/L, respectively. Fish waste inputs to the CDF contributed to mixotrophic denitrification and low sulfate production. A mass balance showed that 7% of the feed nitrogen was assimilated by fish, 6% was removed by passive denitrification (e.g., in anoxic zones in filters), 60% in the CDF and 27% was discharged during sampling and solids removal. Daily fresh water addition was <2% of fish tank volumes. The results are promising as a low cost alternative for saline wastewater denitrification.


Assuntos
Reatores Biológicos , Desnitrificação , Animais , Aquicultura , Processos Autotróficos , Nitratos , Nitrogênio , Enxofre , Águas Residuárias
11.
Chemosphere ; 256: 126952, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32428737

RESUMO

The adjustment of hydraulic retention time (HRT) and the supplement of titanium(III) nitrilotriacetate (Ti(III)-NTA) as a reducing agent were implemented in an anaerobic downflow hanging sponge (DHS) reactor with the aims to (i) improve nitrogen removal performance and to (ii) eliminate N2O emission. A laboratory-scale DHS reactor was operated at 35 °C, under autotrophic denitrification conditions with methane gas (14.2 L d-1) as the main carbon source, NaNO3 and NaNO2 (20 mg N L-1 per compound) as nitrogen sources. The sufficient HRT for simultaneously removing nitrate and nitrite in this reactor was found at 12 h when HRT was reduced from 24 to 6 h. Then at the HRT of 12 h, the addition of Ti(III)-NTA at a final concentration of 25 µM Ti(III) boosted the reactor's nitrogen removal rates from 1.4 ± 0.6 to 4.1 ± 1.9 g NO3--N m-3 d-1 and 3.2 ± 2.8 to 6.6 ± 3.3 g NO2--N m-3 d-1. Furthermore, this study is the first to consider the N2O emission in a continuous reactor applying denitrification coupled to anaerobic methane oxidation (DAMO) process. Produced N2O in this DHS reactor was from 10.6 × 10-4% to 89.0 × 10-4% of removed NOx- without Ti(III)-NTA and from 0.7 × 10-4% to 61.4 × 10-4% of removed NOx- with Ti(III)-NTA. Overall, these findings suggested the advantage of Ti(III)-NTA as an oxygen scavenger for denitrification processes and the potential of the anaerobic DHS reactor for facilitating the DAMO processes and mitigating N2O gas.


Assuntos
Reatores Biológicos , Nitrogênio/metabolismo , Anaerobiose , Processos Autotróficos , Carbono , Desnitrificação , Metano , Nitratos , Nitritos , Óxido Nitroso , Oxirredução , Substâncias Redutoras
12.
Water Res ; 179: 115914, 2020 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-32413614

RESUMO

Iron sulphides, mainly in the form of mackinawite (FeS), pyrrhotite (Fe1-xS, x = 0-0.125) and pyrite (FeS2), are the most abundant sulphide minerals and can be oxidized under anoxic and circumneutral pH conditions by chemoautotrophic denitrifying bacteria to reduce nitrate to N2. Iron sulphides mediated autotrophic denitrification (ISAD) represents an important natural attenuation process of nitrate pollution and plays a pivotal role in linking nitrogen, sulphur and iron cycles in a variety of anoxic environments. Recently, it has emerged as a promising bioprocess for nutrient removal from various organic-deficient water and wastewater, due to its specific advantages including high denitrification capacity, simultaneous nitrogen and phosphorus removal, self-buffering properties, and fewer by-products generation (sulphate, waste sludge, N2O, NH4+, etc.). This paper provides a critical overview of fundamental and engineering aspects of ISAD, including the theoretical knowledge (biochemistry, and microbial diversity), its natural occurrence and engineering applications. Its potential and limitations are elucidated by summarizing the key influencing factors including availability of iron sulphides, low denitrification rates, sulphate emission and leaching heavy metals. This review also put forward two key questions in the mechanism of anoxic iron sulphides oxidation, i.e. dissolution of iron sulphides and direct substrates for denitrifiers. Finally, its prospects for future sustainable wastewater treatment are highlighted. An iron sulphides-based biotechnology towards next-generation wastewater treatment (NEO-GREEN) is proposed, which can potentially harness bioenergy in wastewater, incorporate resources (P and Fe) recovery, achieve simultaneous nutrient and emerging contaminants removal, and minimize waste sludge production.


Assuntos
Desnitrificação , Águas Residuárias , Processos Autotróficos , Reatores Biológicos , Compostos Ferrosos , Ferro , Nitratos , Nitrogênio , Sulfetos , Eliminação de Resíduos Líquidos
13.
J Environ Manage ; 268: 110674, 2020 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-32383647

RESUMO

To avoid hydrogen injection and to enhance the settleability of microbial biomass in biological treatment of nitrate-contaminated drinking water resources, a new method based on granulation of a mixture of hydrogen consumer denitrifiers (HCD) and microalgae is introduced. Decreasing hydraulic retention time (HRT) was applied as the selection pressure in an up-flow photobioreactor to increase the speed of granulation and nitrate removal under autotrophic condition during a 50-day operation. Formation of granules occurred at three phases including granule nucleation, growth of granule, and mature granule, with decreasing the values of ζ-potential from -19 mV to -4 mV. Enhancement of microbial attachment within granule formation could reduce the presence of total suspended solids in the effluent. Developed granules of HCD and microalgae could settle down with velocity of 40 ± 0.6 m/h when reaching the average size of 1.2 mm at day 40. Complete NO3--N removal from drinking water was achieved from the initial stage of granulation until the end of operation at all HRTs of 3 days-5 h. The clear treated water was obtained at the growth phase when the chemical oxygen demand and phosphate were undetectable. Therefore, the application of HCD-microalgae granule is a promising way for nitrate removal from water.


Assuntos
Água Potável , Microalgas , Purificação da Água , Processos Autotróficos , Reatores Biológicos , Desnitrificação , Hidrogênio , Nitratos
14.
Proc Natl Acad Sci U S A ; 117(23): 13168-13175, 2020 06 09.
Artigo em Inglês | MEDLINE | ID: mdl-32471945

RESUMO

Living biological systems display a fascinating ability to self-organize their metabolism. This ability ultimately determines the metabolic robustness that is fundamental to controlling cellular behavior. However, fluctuations in metabolism can affect cellular homeostasis through transient oscillations. For example, yeast cultures exhibit rhythmic oscillatory behavior in high cell-density continuous cultures. Oscillatory behavior provides a unique opportunity for quantitating the robustness of metabolism, as cells respond to changes by inherently compromising metabolic efficiency. Here, we quantify the limits of metabolic robustness in self-oscillating autotrophic continuous cultures of the gas-fermenting acetogen Clostridium autoethanogenum Online gas analysis and high-resolution temporal metabolomics showed oscillations in gas uptake rates and extracellular byproducts synchronized with biomass levels. The data show initial growth on CO, followed by growth on CO and H2 Growth on CO and H2 results in an accelerated growth phase, after which a downcycle is observed in synchrony with a loss in H2 uptake. Intriguingly, oscillations are not linked to translational control, as no differences were observed in protein expression during oscillations. Intracellular metabolomics analysis revealed decreasing levels of redox ratios in synchrony with the cycles. We then developed a thermodynamic metabolic flux analysis model to investigate whether regulation in acetogens is controlled at the thermodynamic level. We used endo- and exo-metabolomics data to show that the thermodynamic driving force of critical reactions collapsed as H2 uptake is lost. The oscillations are coordinated with redox. The data indicate that metabolic oscillations in acetogen gas fermentation are controlled at the thermodynamic level.


Assuntos
Reatores Biológicos/microbiologia , Clostridium/metabolismo , Metabolismo Energético , Fermentação , Processos Autotróficos , Biomassa , Monóxido de Carbono/metabolismo , Hidrogênio/metabolismo , Metabolômica , Oxirredução , Proteômica , Termodinâmica
15.
Bioresour Technol ; 308: 123302, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32276204

RESUMO

Pyrrhotite-sulfur autotrophic denitrification (PSAD) system, using mixture of pyrrhotite and sulfur particle as electron donor, was studied through batch, column and pilot experiments. Treating synthetic secondary effluent at HRT 3 h, the PSAD system obtained the effluent with NO3--N 0.28 ± 0.14 mg·L-1 and without PO43--P to be detected. Thiobacillus was the most abundant autotrophic denitrification bacteria; autotrophic, heterotrophic and sulfate-reducing bacteria coexisted in the PSAD system; phosphate was mainly removed in forms of graftonite, dufrenite, ardealite. The H+ produced in the SAD could accelerate the PAD through promoting pyrrhotite dissolution, and iron ions produced in the PAD could accelerate the SAD through Fe3+/Fe2+ shuttle. Because of the synergistic effects between the pyrrhotite and sulfur, the PSAD system removed nitrate and phosphate deeply and efficiently. It is a promising way to meet the stringent nitrogen and phosphorus discharge standards and to recover phosphorus resources from wastewater.


Assuntos
Desnitrificação , Microbiota , Processos Autotróficos , Reatores Biológicos , Minerais , Nitratos , Nitrogênio , Fosfatos , Enxofre
16.
Bioresour Technol ; 307: 123229, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32247270

RESUMO

The inclusion of S0 hydrolysis in a kinetic model of autotrophic denitrification has been recently proposed; however the model has not been calibrated or validated yet. Thus, a new methodology was developed and applied to calibrate and validate this kinetic model for the first time. An inoculum adapted from a poultry wastewater treatment plant at stoichiometric S0/NO3- ratio was used. The model was calibrated with batch data (initial nitrate concentrations of 50 and 6.25 mg NO3--N/L) at an S0/N ratio = 2.29 mg S/mg N and validated with seven different batch data. The sensitivity analysis showed that the most sensitive parameters are related to S0 hydrolysis. The kinetic model was successfully calibrated with the new methodology and validated, with Theil inequality coefficient values lower than 0.21. Thus, the proposed model and methodology were proved to be well suited for the simulation of elemental sulfur-based autotrophic denitrification in batch systems.


Assuntos
Reatores Biológicos , Desnitrificação , Processos Autotróficos , Calibragem , Nitratos , Enxofre
17.
Environ Sci Technol ; 54(6): 3609-3617, 2020 03 17.
Artigo em Inglês | MEDLINE | ID: mdl-32125831

RESUMO

For the production of edible microbial protein (MP), ammonia generated by the Haber-Bosch process or reclaimed ammonia from waste streams is typically considered as the nitrogen source. These processes for ammonia production are highly energy intensive. In this study, the potential for using nitrogen gas (N2) as a direct nitrogen source for MP production by hydrogen-oxidizing bacteria (HOB) was evaluated. The use of N2 versus ammonium as nitrogen source during the enrichment process resulted in differentiation of the bacterial community composition of the enrichments. A few previously unknown potential N2-fixing HOB taxa (i.e., representatives of the genus Azonexus and the family Comamonadaceae) dominated the enrichments. The biomass yield of a N2-fixing HOB enrichment was 30-50% lower than that of the ammonium-based HOB enrichment from the same inoculum source. The dried biomass of N2-fixing HOB had a high protein content (62.0 ± 6.3%) and an essential amino acid profile comparable to MP from ammonium-based HOB. MP from N2-fixing HOB could potentially be produced in situ without entailing the emissions caused by ammonia production and transportation by conventional means. It could be a promising substitute for N2-fixing protein-rich soybean because it has 70% higher protein content and double energy conversion efficiency from solar energy to biomass.


Assuntos
Processos Autotróficos , Hidrogênio , Bactérias , Nitrogênio , Fixação de Nitrogênio , Oxirredução
18.
Environ Pollut ; 262: 114190, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32193079

RESUMO

Organ carbon are often used to enhance denitrification in wastewater treatment. However, their possible effects on microbial interactions are very limited. In this work, an anaerobic ammonium oxidation (anammox) coupled with sulfur autotrophic/mixotrophic denitrification (SAD/SMD) system was used to investigate the changes in microbial interactions among the microbial communities under different nutrient condition. The removal efficiency of total nitrogen increased from 70% (SAD) to 97% (SMD). The Illumina sequencing analysis indicated that Planctomycetes was the most dominant bacterial phylum in anammox system. Thiobacillus and Sulfurimonas, two typical autotrophic denitrifiers, decreased significantly from 31.9% to 17.7%-12.2% and 9.3%, when the nutrient condition changed from SAD to SMD (P < 0.05). Meanwhile, some heterotrophic or mixotrophic denitrifying bacteria, including Gemmobacter, Pseudomonas and Thauera increased significantly (P < 0.05). Molecular ecological network (MEN) analysis showed that the addition of organic carbon substantially altered the overall architecture of the network. Compared with SAD, the SMD had shorter path lengths, indicating higher transfer efficiencies of information and materials among different microorganism. The addition of organic carbon increased the microbial interaction complexity of Proteobacteria. The links of Thiobacillus, which was a typical sulfur-oxidizing autotrophic denitrifying bacteria, significantly reduced (P < 0.05) with the addition of organic carbon, while the links of the heterotrophic bacteria Geobacter significantly increased (P < 0.05). This study provided new insights into our understanding of the shifts in the bacteria community and their microbial interactions under different nutrient conditions (SAD and SMD) in sulfur-supported denitrification system.


Assuntos
Desnitrificação , Microbiota , Processos Autotróficos , Reatores Biológicos , Nitratos , Nitrogênio , Enxofre
19.
Proc Natl Acad Sci U S A ; 117(13): 7516-7523, 2020 03 31.
Artigo em Inglês | MEDLINE | ID: mdl-32170009

RESUMO

Among CO2-fixing metabolic pathways in nature, the linear Wood-Ljungdahl pathway (WLP) in phylogenetically diverse acetate-forming acetogens comprises the most energetically efficient pathway, requires the least number of reactions, and converts CO2 to formate and then into acetyl-CoA. Despite two genes encoding glycine synthase being well-conserved in WLP gene clusters, the functional role of glycine synthase under autotrophic growth conditions has remained uncertain. Here, using the reconstructed genome-scale metabolic model iSL771 based on the completed genome sequence, transcriptomics, 13C isotope-based metabolite-tracing experiments, biochemical assays, and heterologous expression of the pathway in another acetogen, we discovered that the WLP and the glycine synthase pathway are functionally interconnected to fix CO2, subsequently converting CO2 into acetyl-CoA, acetyl-phosphate, and serine. Moreover, the functional cooperation of the pathways enhances CO2 consumption and cellular growth rates via bypassing reducing power required reactions for cellular metabolism during autotrophic growth of acetogens.


Assuntos
Aminoácido Oxirredutases/metabolismo , Aminometiltransferase/metabolismo , Processos Autotróficos/fisiologia , Complexos Multienzimáticos/metabolismo , Acetilcoenzima A/metabolismo , Aminoácido Oxirredutases/genética , Aminometiltransferase/genética , Proteínas de Bactérias/metabolismo , Ciclo do Carbono , Dióxido de Carbono/metabolismo , Monóxido de Carbono/metabolismo , Clostridium/metabolismo , Redes e Vias Metabólicas , Complexos Multienzimáticos/genética , Família Multigênica , Óxido Nítrico Sintase/genética , Óxido Nítrico Sintase/metabolismo
20.
Aquat Toxicol ; 222: 105463, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32172181

RESUMO

Massive use of glyphosate-based herbicides in agricultural activities has led to the appearance of this herbicide in freshwater systems, which represents a potential threat to these systems and their communities. These herbicides can affect autotrophic and heterotrophic picoplankton abundance. However, little is known about glyphosate impact on the whole structure of these assemblages. Herein, we used an 8-day long microcosm approach under indoor controlled conditions to analyze changes in the structure of picoplankton exposed to a single pulse of glyphosate. The analyzed picoplankton correspond to two outdoor ponds with contrasting states: "clear" (chlorophyll-a = 3.48 µg L-1± 1.15; nephelometric turbidity, NTU = 1) and "turbid" (chlorophyll-a = 105.96 µg L-1 ± 15.3; NTU = 48). We evaluated herbicide impact on different picoplankton cytometric populations and further explored changes in bacterial dominant operational taxonomic units (OTUs) fingerprinting. We observed that glyphosate induced a drastic decrease in the abundance of phycocyanin-rich picocyanobacteria. Particularly, in the turbid system this effect resulted in an 85 % decrease in the abundance of the whole autotrophic picoplankton. Glyphosate also changed the structure of the heterotrophic fraction by means of changing bacterial dominant OTUs fingerprinting patterns in both systems and by shifting the relative abundances of cytometric groups in the clear scenario. These results demonstrate that upon glyphosate exposure picoplanktonic fractions face not only the already reported changes in abundance, but also alterations in the composition of cytometric groups and of bacterial dominant operational taxonomic units. This research provides suitable and still little explored tools to analyze agrochemical effects on picoplanktonic communities.


Assuntos
Processos Autotróficos/efeitos dos fármacos , Glicina/análogos & derivados , Herbicidas/toxicidade , Processos Heterotróficos/efeitos dos fármacos , Plâncton/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Agricultura , Clorofila A/metabolismo , Cianobactérias/efeitos dos fármacos , Cianobactérias/crescimento & desenvolvimento , Cianobactérias/metabolismo , Água Doce/química , Glicina/toxicidade , Plâncton/crescimento & desenvolvimento , Plâncton/metabolismo
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