Phosphate-accumulating Organism Research Articles

Tailored synbiotic powder (functional food) to prevent hyperphosphataemia (kidney disorder)

Hyperphosphataemia is treated with phosphate binders, which can cause adverse effects. Spray-dried synbiotic powder (SP) composed of Lactobacillus casei JCM1134 (a phosphate-accumulating organism; PAO) and Aloe vera is potentially a safer alternative for efficient phosphate removal. In this study, a novel strategy was developed; lysine-derivatized deacetylated A. vera (DAVK) was synthesised and fabricated on phosphate-deficient PAO (PDP) for efficient phosphate transfer and then spray-dried with the supernatant of DAV centrifugation to form a sacrificial layer on PDP for SP integrity during gastric passage. In vitro experiments revealed that PAO removed only 1.6% of the phosphate from synthetic media, whereas SP removed 89%, 87%, and 67% (w/v) of the phosphate from milk, soft drink, and synthetic media, respectively, confirming the protective role of A. vera and efficient phosphate transport. Compared with commercial binders, SP effectively removed phosphate from synthetic media, whereas SP and CaCO3 exhibited comparative results for milk and soft drink. Importantly, CaCO3 caused hypercalcaemia. Thus, the described SP presents a promising tool to prevent hyperphosphataemia. This study also revealed a novel factor: diets of patients with chronic kidney disease should be monitored to determine the optimal phosphate binders, as phosphate removal performance depends on the accessible phosphate forms.

Simultaneous removal of phosphorous and nitrogen by ammonium assimilation and aerobic denitrification of novel phosphate-accumulating organism Pseudomonas chloritidismutans K14

Pseudomonas chloritidismutans K14, a novel phosphate-accumulating organism with the capacity to perform ammonium assimilation, aerobic denitrification, and phosphorus removal, was isolated from aquaculture sediments. It produced no hemolysin, and showed susceptibility to most antibiotics. Optimum conditions were achieved with sodium pyruvate as a carbon source, a C/N ratio of 10, pH of 7.5, temperature of 27 °C, P/N ratio of 0.26, and shaking at 140 rpm. Under optimum conditions, the highest removal efficiencies of ammonium, nitrite, and nitrate were 99.82%, 99.11%, and 99.78%, respectively; the corresponding removal rates were 6.27, 4.51, and 4.99 mg/L/h. The strain removed over 98% of phosphorus, and over 87% of chemical oxygen demand. The highest biomass nitrogen during ammonium assimilation was 99.18 mg/L; no gaseous nitrogen was produced. The genes involved in nitrogen and phosphorus removal were amplified by PCR. This study demonstrated the potential application prospects of strain K14 for nitrogen and phosphorus removal.

Simultaneous aerobic removal of phosphorus and nitrogen by a novel salt-tolerant phosphate-accumulating organism and the application potential in treatment of domestic sewage and aquaculture sewage

Phosphorus (P) and nitrogen (N) pollution are the worldwide challenging problem. In the present study, a new salt-tolerant phosphate-accumulating organism (PAO) was isolated and identified as Bacillus subtilis GHSP10. Strain GHSP10 did not produce hemolysin and showed high susceptibility to antibiotics. The favorable phosphorus removal C/N ratios, P/N ratios, temperature, salinities, pH values and shaking speeds of strain GHSP10 were 10–20, 0.1–0.2, 28 °C, 0–3%, 7.5–8.5 and 100–250 r/min. Besides, strain GHSP10 could conduct heterotrophic nitrification–aerobic denitrification and the maximal removal efficiencies of ammonium, nitrite and nitrate were 99.52%, 81.10% and 95.84% respectively. Moreover, the phosphorus removal process of strain GHSP10 was achieved under entirely aerobic conditions, and glycogen and poly-β-hydroxybutyrate could provide energy source for the phosphorus removal process of strain GHSP10. The amplification of ppk, hao, napA, narG, nirK genes as well as the expression of polyphosphate kinase helped to reveal the removal pathways of phosphorus and nitrogen, providing theoretical support for the phosphorus removal, nitrification and aerobic denitrification abilities of strain GHSP10. Furthermore, efficient removal of phosphorus and nitrogen from both domestic sewage and aquaculture sewage could be accomplished by strain GHSP10. This study may provide a hopeful candidate strain for simultaneous removal of phosphorus and nitrogen pollution from both freshwater sewage and saline sewage.

Complete nitrogen removal via simultaneous nitrification and denitrification by a novel phosphate accumulating Thauera sp. strain SND5

Bacteria capable of simultaneous nitrification and denitrification (SND) and phosphate removal could eliminate the need for separate reactors to remove nutrients from wastewater and alleviate competition for carbon sources between different heterotrophs in wastewater treatment plants (WWTPs). Here we report a newly isolated Thauera sp. strain SND5, that removes nitrogen and phosphorus from wastewater via SND and denitrifying-phosphate accumulation, respectively, without accumulation of metabolic intermediates. Strain SND5 simultaneously removes ammonium, nitrite, and nitrate at an average rate of 2.85, 1.98, and 2.42 mg-N/L/h, respectively. Batch testing, detection of functional genes, nitrogenous gas detection and thermodynamic analysis suggested that nitrogen gas, with hydroxylamine produced as an intermediate, was the most likely end products of heterotrophic ammonium oxidation by strain SND5. The generated end products and intermediates suggest a novel nitrogen removal mechanism for heterotrophic ammonium oxidation in strain SND5 (NH4+→NH2OH→N2). Strain SND5 was also found to be a denitrifying phosphate-accumulating organism, capable of accumulating phosphate, producing and storing polyhydroxybutyrate (PHB) as an intracellular source of carbon while using nitrate/nitrite or oxygen as an electron acceptor during PHB catabolism. This study identifies a novel pathway by which simultaneous nitrogen and phosphorus removal occurs in WWTPs via a single microbe.

Phosphorus and nitrogen removal by a novel phosphate-accumulating organism, Arthrobacter sp. HHEP5 capable of heterotrophic nitrification-aerobic denitrification: Safety assessment, removal characterization, mechanism exploration and wastewater treatment

A novel phosphate-accumulating organism (PAO), Arthrobacter sp. HHEP5 was isolated from mariculture effluents. It produced no hemolysin and was susceptible to most antibiotics. It had removal efficiencies of above 99% for 1–10 mg/L phosphorus at 18–28 °C, pH 5.5–8.5, salinities 0–3%, C/N ratios 5–20, P/N ratios 0.1–0.2 and 20–260 rpm. It exhibited simultaneous aerobic phosphorus removal, nitrification and denitrification with the highest ammonium, nitrite, nitrate removal efficiencies of 99.87%, 100%, 99.37%. Phosphorus removal was accomplished by assimilating phosphate with the existence of polyphosphate kinase completely under aerobic condition. Genes involved in nitrogen removal were amplified. 99% of phosphorus and 95% of nitrogen in both mariculture and domestic wastewater were removed by HHEP5. This study provided sound methods for future screening of PAOs and new perspectives for renewed cognition of phosphorus removal process. Wide adaptation and remarkably aerobic phosphorus, nitrogen removal performances would make HHEP5 a promising candidate in wastewater treatment.

Isolation and appraisal of a non-fermentative bacterium, Delftia tsuruhatensis, as denitrifying phosphate-accumulating organism and optimal growth conditions

Eutrophication caused by excessive nitrogen, phosphorous in water body has considerably serious impacts on the production and life of human being. Activated sludge, a biological removal process, is regarded as a promising and sustainable technology for wastewater treatment. In this study, a novel strain of denitrifying phosphate-accumulating organism (DPAO) was isolated from the activated sludge conducted the acclimation of anaerobic/anoxic (A/O) stage and anaerobic/aerobic (A/A) stage. The removal efficiencies of NO3−-N and PO43--P in bioreactor were 98.7 % and 90.7 % respectively. The metabolic activity of DPAOs was improved from 34.43%–98.28% after A/A stage. The genetic identification and morphological and biochemical characteristics of isolated strain were analyzed and discussed to determine it as a non-fermentative Delftia tsuruhatensis. Sodium acetate and ammonium sulfate + peptone were testified to be optimal carbon source and nitrogen for the growth of this strain respectively. Furthermore, the orthogonal test was measured and calculated to find that the order of key factors affecting the growth of this strain was pH > nitrogen > carbon. According to computer response surface methodology, the most suitable medium group for this strain as 4450 mg/L of sodium acetate (carbon source), 1320 mg/L of ammonium sulfate + peptone (nitrogen source) and 7.85 of pH. The findings of this work broadened up our comprehension of the biological removal process for DPAOs during enhanced biological phosphorus removal.

Effects of operational models (batch, continuous and CFID modes) on the performance of a single A2O airlift bioreactor for treatment of milk processing wastewater

This study surveys the effect of different operational models, batch, continuous, and continuous feeding with intermittent discharge (CFID), on the performance of an air lift reactor (ALR) and a stirred tank reactor (STR) in terms of simultaneous removal of CNP from milk processing wastewater. The experimental data were recorded under similar operating conditions with HRT of 10h, air flow rate of 2l/min, and biomass concentration of 5–6g/l. The obtained results indicated that the CFID mode was a promising regime which ensured the occurrence of anaerobic, anoxic, and aerobic conditions in the air lift bioreactor. This gave favorable conditions for simultaneous COD and nutrient removal processes in one compartment. At the optimum condition obtained, 170mg/l (79%) of total nitrogen (TN) and 25mg/l (63%) phosphorus (TP) were removed in the CFID-ALR, while, batch and continuous operational conditions did not create anaerobic and efficient anoxic zones in the air lift bioreactor. The ALR was more effective to remove nutrients when compared to the STR at all different operational modes studied. The microbial community at different experimental conditions was also investigated to detect Candidatus Accumulibactor as a common species of phosphate accumulating organism (PAOs) through PCR method. From the PCR results, Candidate Accumulibactor was detected in the CFID-ALR, underpinning the observed TP removal.

Deciphering the relationship among phosphate dynamics, electron-dense body and lipid accumulation in the green alga Parachlorella kessleri.

Phosphorus is an essential element for life on earth and is also important for modern agriculture, which is dependent on inorganic fertilizers from phosphate rock. Polyphosphate is a biological polymer of phosphate residues, which is accumulated in organisms during the biological wastewater treatment process to enhance biological phosphorus removal. Here, we investigated the relationship between polyphosphate accumulation and electron-dense bodies in the green alga Parachlorella kessleri. Under sulfur-depleted conditions, in which some symporter genes were upregulated, while others were downregulated, total phosphate accumulation increased in the early stage of culture compared to that under sulfur-replete conditions. The P signal was detected only in dense bodies by energy dispersive X-ray analysis. Transmission electron microscopy revealed marked ultrastructural variations in dense bodies with and without polyphosphate. Our findings suggest that the dense body is a site of polyphosphate accumulation, and P. kessleri has potential as a phosphate-accumulating organism.

A metabolic network of a phosphate-accumulating organism provides new insights into enhanced biological phosphorous removal

Here we present a metabolic network representing the central carbon metabolism as well as the synthesis of polyhydroxyalcanohates and the polyphosphate accumulation mechanisms of the bacterium Candidatus Accumulibacter phosphatis, which was previously identified from metagenomic studies in enhanced biological phosphorous removal sludges. The reconstructed metabolic network, together with flux balance analysis can be used to provide new insights into controversial aspects of the metabolism of phosphate-accumulating organisms and is also a tool that can be used in to help enhanced biological phosphorous removal (EBPR) process design and operation.

Accumulation of inorganic polyphosphates in Saccharomyces cerevisiae under nitrogen deprivation: Stimulation by magnesium ions and peculiarities of localization

The yeast Saccharomyces cerevisiae was shown to have a high potential as a phosphate-accumulating organism under growth suppression by nitrogen limitation. The cells took up over 40% of phosphate from the medium containing 30 mM glucose and 5 mM potassium phosphate and over 80% of phosphate on addition of 5 mM magnesium sulfate. The major part of accumulated Pi was reserved as polyphosphates. The content of polyphosphates was ∼57 and ∼75% of the phosphate accumulated by the cells in the absence and presence of magnesium ions, respectively. The content of long-chain polyphosphates increased in the presence of magnesium ions, 5-fold for polymers with the average length of ∼45 phosphate residues, 3.7-fold for polymers with the average chain length of ∼75 residues, and more than 10-fold for polymers with the average chain length of ∼200 residues. On the contrary, the content of polyphosphates with the average chain length of ∼15 phosphate residues decreased threefold. According to the data of electron and confocal microscopy and X-ray microanalysis, the accumulated polyphosphates were localized in the cytoplasm and vacuoles. The cytoplasm of the cells accumulating polyphosphates in the presence of magnesium ions had numerous small phosphorus-containing inclusions; some of them were associated with large electron-transparent inclusions and the cytoplasmic membrane.

A predictive model for the reactor inorganic suspended solids concentration in activated sludge systems

A simple predictive model for the activated sludge reactor inorganic suspended solids (ISS) concentration (excluding that from chemical precipitant dosing) is presented. It is based on the accumulation of influent ISS in the reactor and an ordinary heterotrophic organism (OHO) ISS content (fiOHO) of 0.15 mg ISS/mg OHO organic (volatile) suspended solids (VSS) and a variable phosphate accumulating organism (PAO) ISS content (fiPAO) proportional to their P content (fXBGP). Organism ISS content is conceptualized as the uptake of dissolved inorganic solids by active organisms, which when dried in the total suspended solids (TSS) test procedure, precipitate and manifest as ISS. The model is validated with data from 22 investigations conducted over the past 15 years on 30 aerobic and anoxic-aerobic nitrification-denitrification (ND) systems and 18 anaerobic-anoxic-aerobic ND biological excess P removal (BEPR) systems variously fed artificial and real wastewater, and operated from 3 to 20 days sludge age. The predicted reactor VSS/TSS ratio reflects the observed relative sensitivity to sludge age, which is low, and to BEPR, which is high. To use the model for design, two parameters need to be known: (1) the influent ISS concentration, which is not commonly measured in wastewater characterization analyses and (2) the P content of PAOs (fXBGP), which can vary considerably depending on the extent of anoxic P uptake BEPR that takes place in the system. Some guidance on the measurement of influent ISS concentration and selection of the PAO P content to calculate the mixed liquor VSS/TSS ratio for design is given.

Modelling inorganic material in activated sludge systems

A simple predictive model for the activated sludge reactor inorganic suspended solids (ISS) concentration is presented. It is based on the accumulation of influent ISS in the reactor and an ordinary heterotrophic organism (OHO) ISS content (fiOHO) of 0.15 mg ISS/mgOHOVSS and a variable phosphate accumulating organism (PAO) ISS content (fiPAO) proportional to their P content (fXBGP). The model is validated with data from 21 investigations conducted over the past 15 years on 30 aerobic and anoxic-aerobic nitrification denitrification (ND) systems and 18 anaerobic-anoxic-aerobic ND biological excess P removal (BEPR) systems variously fed artificial and real wastewater and operated from 3 to 20 d sludge age. The predicted reactor VSS/TSS ratio reflects the observed relative sensitivity to sludge age, which is low, and to BEPR, which is high. For effective use of the model for design, two significant issues require attention: measurement of the influent ISS concentration, which is not commonly done in wastewater characterisation analyses; and estimating a priori the P content of PAOs (fXBGP), which can vary considerably depending on the extent of anoxic P uptake BEPR that takes place in the system. Some guidance on selection of the mixed liquor VSS/TSS ratio for design is given. WaterSA Vol.30 (2) 2004: 153-174

The influence of anaerobic reaction time on the fraction of denitrifying phosphate accumulating organism in BNR precesses

This study investigated the influence of anaerobic reaction time on the fraction of denitrifying phosphate accumulating organisms (DNPAO) to total phosphate accumulating organisms (PAOs) using a series of batch experiments. The results showed that the DNPAO increased as the anaerobic reaction time increased. This implied that the PHA (polyhydroxyalkanoates) accumulating rate of DNPAO was lower than that of non‐denitrifying phosphate accumulating organisms (non‐DNPAO). Thus, the DNPAO required a longer anaerobic reaction time to reach the saturated intracellular PHA level. Furthermore, more than two hours of anaerobic hydraulic retention time is necessary when designing an enhanced DNPAO process.

Difficulties and developments in biological nutrient removal technology and modelling

Filamentous bulking and the long sludge age required for nitrification are two important factors that limit the wastewater treatment capacity of biological nutrient removal (BNR) activated sludge systems. A growing body of observations from full-scale plants indicate support for the hypothesis that a significant stimulus for filamentous bulking in BNR systems in alternating anoxic-aerobic conditions with the presence of oxidized nitrogen at the transition from anoxic to aerobic. In the DEPHANOX system, nitrification takes place externally allowing sludge age and filamentous bulking to be reduced and increases treatment capacity. Anoxic P uptake is exploited in this system but it appears that this form of biological excess P removal (BEPR) is significantly reduced compared with aerobic P uptake in conventional BNR systems. Developments in the understanding of the BEPR processes of (i) phosphate accumulating organism (PAO) denitrification and anoxic P uptake, (ii) fermentation of influent readily biodegradable (RB)COD and (iii) anaerobic hydrolysis of slowly biodegradable (SB)COD are evaluated in relation to the IAWQ Activated Sludge Model (ASM) No.2. Recent developments in BEPR research do not yet allow a significant improvement to be made to ASM No. 2 that will increase its predictive power and reliability and therefore it remains essentially as a framework to guide further research.

Difficulties and developments in biological nutrient removal technology and modelling

Filamentous bulking and the long sludge age required for nitrification are two important factors that limit the wastewater treatment capacity of biological nutrient removal (BNR) activated sludge systems. A growing body of observations from full-scale plants indicate support for the hypothesis that a significant stimulus for filamentous bulking in BNR systems in alternating anoxic-aerobic conditions with the presence of oxidized nitrogen at the transition from anoxic to aerobic. In the DEPHANOX system, nitrification takes place externally allowing sludge age and filamentous bulking to be reduced and increases treatment capacity. Anoxic P uptake is exploited in this system but it appears that this form of biological excess P removal (BEPR) is significantly reduced compared with aerobic P uptake in conventional BNR systems. Developments in the understanding of the BEPR processes of (i) phosphate accumulating organism (PAO) denitrification and anoxic P uptake, (ii) fermentation of influent readily biodegradable (RB)COD and (iii) anaerobic hydrolysis of slowly biodegradable (SB)COD are evaluated in relation to the IAWQ Activated Sludge Model (ASM) No.2. Recent developments in BEPR research do not yet allow a significant improvement to be made to ASM No. 2 that will increase its predictive power and reliability and therefore it remains essentially as a framework to guide further research.