By-product Ammonia Research Articles

Study on the mechanism and stability of microbially induced struvite precipitation (MISP) for enhanced immobilization of uranium

The microbial induced carbonate precipitation (MICP) technique has been shown to immobilize a wide range of heavy metals. However, the MICP process for removing uranium-dominated composite heavy metals ignores the formation of substances such as uranyl carbonate, which can easily lead to uranium migration. Furthermore, the by-product ammonia is one of the bottlenecks limiting the application of MICP. In this work, the microbially induced struvite precipitation (MISP) method was used to enhance U immobilization while reducing by-product contamination. The results showed that the optimal uranium removal rate of the MISP process was increased by 82.98% compared to the MICP. Characterization results confirmed the co-precipitation of U with NH4+ in the form of uramphite and struvite, while the participation of U changed the mineral crystal shape. Stability experiments showed that the maximum release of U from struvite was only 1.27%, which is much lower than the minimum release of U from CaCO3. As a result, the MISP process both enhanced uranium immobilization efficiency, decreased the risk of uranium migration-release, and reduced the environmental impact of the by-product ammonia. These results provided a new perspective for studying U contamination remediation and its co-precipitation behavior in microbial mineralization.

Self‐foaming polyurea foams reinforced by nano SiO2 via a non‐isocyanate route

AbstractThe feedstocks for conventional polyurea foams (PUrFs) are limited but they have more choices in urea route as discribed in this work. Urea, ternary amine T403 and diaminodecane DA‐10 were used for the construction of self‐foaming PUrFs, in which the byproduct ammonia performs as a foaming agent. The influence of nano SiO2 content and feeding ratio of T403 to DA‐10 on the pore morphology and the properties of PUrFs were investigated. A feeding amount of 3 wt% nano SiO2 is found to be able to significantly improve the nucleation performance of PUrFs. If the nano SiO2 loading is higher (5 wt%) the melt strength will increase, which is not benefit for the foaming. An appropriate feeding ratio of T403 to DA‐10 (1/1, sample PUrF‐3‐50) can improve the crystallinity thus promoting the nucleation in foaming process. The comprehensive performance of PUrF‐3‐50 is found to be the highest, with an average pore size at 429 μm, an apparent density at 298 kg/m3, and a compressive strength (75% strain) at 3.2 MPa. It is worth noting that the hysteresis of PUrF‐3‐50 is high (>90%) and stable. This work provides a new strategy for the preparation of PUrFs and broadens the applications of urea‐based polymers.

Ammonia detoxification promotes CD8+ T cell memory development by urea and citrulline cycles.

Amino acid metabolism is essential for cell survival, while the byproduct ammonia is toxic and can injure cellular longevity. Here we show that CD8+ memory T (TM) cells mobilize the carbamoyl phosphate (CP) metabolic pathway to clear ammonia, thus promoting memory development. CD8+ TM cells use β-hydroxybutyrylation to upregulate CP synthetase 1 and trigger the CP metabolic cascade to form arginine in the cytosol. This cytosolic arginine is then translocated into the mitochondria where it is split by arginase 2 to urea and ornithine. Cytosolic arginine is also converted to nitric oxide and citrulline by nitric oxide synthases. Thus, both the urea and citrulline cycles are employed by CD8+ T cells to clear ammonia and enable memory development. This ammonia clearance machinery might be targeted to improve T cell-based cancer immunotherapies.

Astrocytic urea cycle detoxifies Aβ-derived ammonia while impairing memory in Alzheimer’s disease

Alzheimer's disease (AD) is one of the foremost neurodegenerative diseases, characterized by beta-amyloid (Aβ) plaques and significant progressive memory loss. In AD, astrocytes are proposed to take up and clear Aβ plaques. However, how Aβ induces pathogenesis and memory impairment in AD remains elusive. We reportthat normal astrocytes show non-cyclic urea metabolism, whereas Aβ-treated astrocytes show switched-on urea cycle with upregulated enzymes and accumulated entering-metabolite aspartate, starting-substrate ammonia, end-product urea, and side-product putrescine. Gene silencing of astrocytic ornithine decarboxylase-1 (ODC1), facilitating ornithine-to-putrescine conversion, boosts urea cycle and eliminates aberrant putrescine and its toxic byproducts ammonia and H2O2 and its end product GABA to recover from reactive astrogliosis and memory impairment in AD. Our findings implicate that astrocytic urea cycle exerts opposing roles of beneficial Aβ detoxification and detrimental memory impairment in AD. We propose ODC1 inhibition as a promising therapeutic strategy for AD to facilitate removal of toxic molecules and prevent memory loss.

Combining microbially induced calcite precipitation (MICP) with zeolite: A new technique to reduce ammonia emission and enhance soil treatment ability of MICP technology

The byproduct ammonia limits the wide application of the urea-hydrolysis based microbially induced calcite precipitation (MICP) technique. Here, we proposed a new technique termed the “MICP-zeolite technique” to reduce ammonia emission, which combined ammonia removal by zeolite with the MICP process. To understand the new technique, 1) the ability of the used zeolite to adsorb bacteria and remove ammonia was tested; 2) the MICP and MICP-zeolite techniques were applied to soils via both a mixing way and an injecting way to evaluate their performance in ammonia emission, soil cementation, and permeability reduction; 3) many properties of the zeolite and treated/untreated sands were characterized including surface charge, microstructure, surface area, pore size distribution. The results present that the zeolite can adsorb Sporosarcina pasteurii strongly, due to its larger specific surface area, rougher and outwardly-protruding surface, and less negative charge. Contact time, pH, temperature, and zeolite dosage affected ammonia removal efficiency. The MICP-zeolite technique resulted in less ammonia emission, greater soil strength, and lower permeability, and the injecting way is more effective in soil cementation. In soils treated by the proposed technique, the clogged pores were more, the precipitated crystals were more and smaller, the number of micropores and macropores reduced more, and the zeta-potential of particles increased more. Collectively, the MICP-zeolite technique is superior to the MICP technique in treatment effect and environmental friendliness.

Composite Polyvinylpyrrolidone-Sodium Alginate-Hydroxyapatite Hydrogel Films for Bone Repair and Wound Dressings Applications.

Today, the synthesis of biocompatible and bioresorbable composite materials such as “polymer matrix-mineral constituent,” which stimulate the natural growth of living tissues and the restoration of damaged parts of the body, is one of the challenging problems in regenerative medicine. In this study, composite films of bioresorbable polymers of polyvinylpyrrolidone (PVP) and sodium alginate (SA) with hydroxyapatite (HA) were obtained. HA was introduced by two different methods. In one of them, it was synthesized in situ in a solution of polymer mixture, and in another one, it was added ex situ. Phase composition, microstructure, swelling properties and biocompatibility of films were investigated. The crosslinked composite PVP-SA-HA films exhibit hydrogel swelling characteristics, increasing three times in mass after immersion in a saline solution. It was found that composite PVP-SA-HA hydrogel films containing HA synthesized in situ exhibited acute cytotoxicity, associated with the presence of HA synthesis reaction byproducts—ammonia and ammonium nitrate. On the other hand, the films with HA added ex situ promoted the viability of dental pulp stem cells compared to the films containing only a polymer PVP-SA blend. The developed composite hydrogel films are recommended for such applications, such as membranes in osteoplastic surgery and wound dressing.

The dynamic process of dietary soybean β-conglycinin in digestion, absorption, and metabolism among different intestinal segments in grass carp (Ctenopharyngodon idella).

The present study aimed to investigate the dynamic process of soybean β-conglycinin in digestion, absorption, and metabolism in the intestine of grass carp (Ctenopharyngodon idella). Fish fed with 80g β-conglycinin/kg diet for 7weeks, the intestinal digestive enzyme was extracted to hydrolyze β-conglycinin in vitro, the free amino acid and its metabolism product contents in intestinal segments were analyzed. The present study first found that β-conglycinin cannot be thoroughly digested by fish intestinedigestive enzyme and produces new products (about 60- and 55-kDa polypeptides). The indigestible β-conglycinin further caused the free amino acid imbalance, especially caused free essential amino acid deficiency in the proximal intestine but excess in the distal intestine. Moreover, these results might be partly associated with the effect of β-conglycinin in amino acid transporters and tight junction-regulated paracellular pathway. Finally, dietary β-conglycinin increased the content of amino acid catabolism by-product ammonia while decreased the amino acid anabolism product carnosine content in the proximal intestine and distal intestine. Thus, the current study first and systemically explored the dynamic process of β-conglycinin in digestion, absorption, and metabolism, which further supported our previous study that dietary β-conglycinin suppressed fish growth and caused intestine injure.

Interfacial electronic effects of palladium nanocatalysts on the by-product ammonia selectivity during nitrite catalytic reduction

Modulating the electronic structure of catalyst atoms (Pd) can significantly influence the selectivity for ammonia during the catalytic reduction of nitrite.

Kinetic Modelling of Automotive Exhaust NO x Reduction over Platinum

The combination of NOx storage and reduction and in situ NH3 selective catalytic reduction (NSR–SCR) provides the benefits of simple structure, no external source of NH3, low precious metal consumption and high NOx reduction efficiency. The by-product ammonia is of importance in the NSR–SCR coupling system. Considering the formation of ammonia and another important side product N2O during the regeneration period of NSR, detailed mechanisms of H2–NO and CO–NO reactions over Pt were developed. The mechanisms of H2–NO and CO–NO reaction systems, which share the same NOx chemistries, are capable of reproducing experimental results from literature. Ammonia was shown highly sensitive to H2/NO feed ratio. NH3 was formed at low temperatures and decomposed with increase of temperature. For different feed conditions, NHx related reactions showed similar influential tendency on NH3 generation, while the hydrogenation of NH showed much greater influence than the other two reactions. In CO–NO reaction system, the intermediate species N2O formed at low temperatures and reached a maximum production at about 320 °C. N2O decomposed into target product N2 when temperature was further increased. The results of coverage and sensitivity analysis indicated that adsorbed CO(s) occupied most catalytic active sites over the whole temperature range of 100–500 °C investigated and showed strong adsorption energy, hindering NO adsorption process and NO(s) dissociation. As a result, the inadequacy of N(s) species reduced the production of N2 and N2O.

Catalysis effect and conversion process of transition metal chlorides in the synthesis of diethyl carbonate from ethyl carbamate and ethanol

The catalysis effect of transition metal chlorides (TMC) for the synthesis of diethyl carbonate (DEC) from ethyl carbamate and ethanol was investigated in a batch reactor. Their activities were arranged as follows: MnCl2 > CoCl2 > ZnCl2 > CdCl2 > NiCl2, the corresponding yields of DEC were 11, 6.5, 3.7, 2.8, and 2.4 % at 190 °C in 12 h. The highest decomposition temperatures of their diammine complexes were sorted as follows: Ni(NH3)2Cl2 > Mn(NH3)2Cl2 > Co(NH3)2Cl2 > Cd(NH3)2Cl2 > Zn(NH3)2Cl2. These results indicated that the activity of TMC was not entirely determined by its ammonia capture ability, which is characterized by the decomposition temperature of diammine complex. On the other hand, the diammine TMC still showed activity for the synthesis of DEC. Their activities were a little lower than those of the corresponding TMC but the sequence was the same to that of TMC. In the reaction process, TMC was found to be coordinated with byproduct ammonia yielded in situ to form ammine complex, in which the number of ammonia molecule would change with the reaction conditions. These results indicated that the catalysis ability of TMC was the crucial influence factor for DEC yield and the reaction coupling ability of it was also benefit for DEC synthesis.

Active Role of the Substrate During Catalysis by the Therapeutic Enzyme L‐Asparaginase II

Bacterial type II L‐Asparaginases (ASPII) have been used for over four decades to treat acute lymphoblastic leukemia, yet a full reaction mechanism remains unknown. ASPII enzymes catalyze the deamidation of both asparagine (Asn) and glutamine (Gln), which results in the formation of aspartate (Asp) and glutamate (Glu) respectively, and the by‐product ammonia. Proposed ASPII mechanisms to date have yet to explain the absolute requirement of a substrate α‐carboxyl group, and clearly identify the role of the catalytic threonines T12 and T89. Here, we study the reaction mechanism of asparagine degradation by ASPII through ab initio molecular dynamics (MD) simulations. We select a reduced system from the substrate‐bound enzyme obtained by classical MD, and explore different initial reaction pathways by driving the system in steered simulations. Our results show that direct nucleophilic attack by T12 produces a highly unstable substrate‐enzyme intermediate, as the stabilization provided by the nearby protons (i.e., the “oxyanion hole”) is insufficient to sustain the high energy state. We find that the substrate‐enzyme intermediate can be stabilized by first protonating the substrate's amide oxygen through the K162‐T89 proton bridge. Furthermore, the α‐carboxyl of the substrate acts as a proton acceptor for the hydroxyl sidechain of T12 during nucleophilic attack. We conclude by showing that a complete deamidation mechanism may require a sequence of several nucleophilic attacks by both T12 and T89, with K162 playing a critical role as a proton buffer during the course of the reaction.

Nitrilase-catalyzed hydrolysis of 3-aminopropionitrile at high concentration with a tandem reaction strategy for shifting the reaction to β-alanine formation

Given the importance of β-alanine, the nitrilase BjNIT3397 from Bradyrhizobium japonicum strain USDA110 was examined toward the hydrolysis of 3-aminopropionitrile. It has been found that nitrilase BjNIT3397 effectively hydrolyzed 3-aminopropionitrile with substrate concentration up to 3M (210g/L) at the pH 7.3 and temperature 30°C. With the increase of substrate concentration from 0.6 to 3M, 3-aminopropanamide was formed and its percentage in the products was increased up to 33%. In order to reduce the formation of 3-aminopropanamide, aspartate ammonia-lyase and fumaric acid were added into the reaction system to consume the byproduct ammonia. As expected, the reaction was shifted toward the formation of β-alanine, resulting in the decrease of 3-aminopropanamide from 33% to 3%. Therefore, a tandem reaction strategy was developed to effectively prevent the formation of 3-aminopropanamide. This might also offer a possibility of producing β-alanine and l-aspartic acid in one process.

Active Role of the Substrate during Catalysis by the Therapeutic Enzyme L-Asparaginase II

Bacterial type II L-Asparaginases (ASPII) have been used for over four decades to treat acute lymphoblastic leukemia, yet a full reaction mechanism remains unknown. ASPII enzymes catalyze the deamidation of both asparagine (Asn) and glutamine (Gln), which results in the formation of aspartate (Asp) and glutamate (Glu) respectively, and the by-product ammonia. Proposed ASPII mechanisms to date have yet to explain the absolute requirement of a substrate α-carboxyl group, and clearly identify the role of the catalytic threonines T12 and T89. Here, we study the reaction mechanism of asparagine degradation by ASPII through ab initio molecular dynamics (MD) simulations. We selected a reduced system from the substrate-bound enzyme obtained by classical MD, and explore different initial reaction pathways by driving the system in steered simulations. Our results show that direct nucleophilic attack by T12 produces a highly unstable substrate-enzyme intermediate, as the stabilization provided by the nearby protons (i.e., the “oxyanion hole”) is insufficient to sustain the high energy state. We find that the substrate-enzyme intermediate can be stabilized by first protonating the substrate's amide oxygen through the K162-T89 proton bridge. Furthermore, the α-carboxyl of the substrate acts as a proton acceptor for the hydroxyl sidechain of T12 during nucleophilic attack. We conclude by showing that a complete deamidation mechanism may require a sequence of several nucleophilic attacks by both T12 and T89, with K162 playing a critical role as a proton buffer during the course of the reaction.

Effects of graphitic carbon nitride on the dehydrogenation of ammonia borane

By ball milling carbon nitride (C 3 N 4 ) and ammonia borane (AB), the AB-C 3 N 4 system was successfully synthesized. It is shown that the dehydrogenation temperature of the AB-C 3 N 4 system was obviously decreased. However, the concentration of byproduct ammonia was much higher than that of pristine AB. Thus, LiBH 4 -modified C 3 N 4 (LC 3 N 4 ) was produced and employed to synthesize a AB-LC 3 N 4 system. The dehydrogenation of the AB-LC 3 N 4 system was investigated using X-ray diffraction, temperature-programmed desorption-mass spectrometry, thermogravimetry-differential thermal analysis, and nuclear magnetic resonance. The results show that the dehydrogenation temperatures of the AB-LC 3 N 4 systems were reduced to a lower region compared with pristine AB. Moreover, byproduct borazine and the induction period were significantly suppressed. After LiBH 4 modification on C 3 N 4 , the other byproduct ammonia was also reduced in the dehydrogenation process. Dynamic analysis and NMR characterization results show that the decomposition mechanism of AB-LC 3 N 4 still follows the self-decomposition of AB, which is induced by the formation of NH 3 BH 2 NH 3 BH 4 . The dehydrogenation temperature of C 3 N 4 -modified ammonia borane was reduced to lower region with depression of byproduct and induction period compared with pristine ammonia borane.

Synthesis of Ethylene Carbonate from Urea and Ethylene Glycol over La(NO<sub>3</sub>)<sub>3</sub> Catalyst

Synthesis of ethylene carbonate (EC) from urea and ethylene glycol was investigated in a batch reactor using La(NO3)3 as catalyst. The reaction was performed under reduced pressure to remove the byproduct ammonia. The effect of various operation conditions such as reaction temperature, reaction time and reaction pressure on the EC yield was explored. It was found that the reaction pressure is a key parameter for the formation of EC. At atmospheric pressure, the reaction cannot happen. As the reaction pressure decreases, the EC yield increases significantly. Under the optimum operation conditions, which are reaction pressure 15 KPa, reaction temperature 413 K, reaction time 3 h, and catalyst concentration 10 wt.%, the EC yield can reach to 93%.

Kinetics studies of dimethyl carbonate synthesis from urea and methanol over ZnO catalyst

A kinetic experiment of dimethyl carbonate (DMC) synthesis by urea methanol over ZnO catalyst was carried out in an isothermal fixed-bed reactor. A kinetic model based on the mole fraction was proposed and the kinetic parameters were estimated from the experimental results. The model predictions were compared with the experimental data and fair agreements were found. The effects of the reaction temperature (443–473 K), space time (0–4.7 h mol−1 kgcat) and urea mass percent (5–9%) in feed on DMC mole fraction were investigated. It was found that the reactions are mainly influenced by the reaction temperature and space time rather than urea mass percent in feed. The experimental and simulated results indicated that the reaction from MC to DMC was the rate-controlling step in the DMC synthesis process from urea and methanol. It is important to remove the DMC and byproduct ammonia to achieve a high selectivity of DMC. This implies that reactive distillation might be used in the DMC synthesis on an industrial scale to achieve a higher selectivity of DMC.

CHO‐K1 host cells adapted to growth in glutamine‐free medium by FACS‐assisted evolution

During the process of recombinant cell line optimisation for production of biopharmaceuticals, multiple cellular properties like robustness against stress, the attainment of high cell concentrations and maintenance of high viability must be considered to maximize protein yield. To improve growth and viability, glutamine is supplemented as an alternative energy source for rapidly dividing cells that oxidize glucose inefficiently. However, the resulting by-product ammonia is toxic at high concentrations and has a negative impact on protein glycosylation, a major quality-determining parameter of biopharmaceuticals. In this work, the CHO-K1 cell line was adapted to a chemically defined medium and suspension growth within 3 weeks. Subsequently, the glutamine concentration was stepwise reduced from 8 to 4 and 2 mM. After each reduction, both the final cell concentration in the batch and the viability decreased. To force a rapid evolution of cells to achieve high final cell concentrations, cells were seeded at high densities (10(7) cells/mL) and surviving cells were sorted by FACS or MACS when viability declined to 10% (typically after 24 h). Sorted cells were grown in batch until viability declined to 10% and viable cells recovered again. The final sorted population was able to reach comparable or even better viable cell concentrations and showed a significantly improved viability compared to their ancestors. The 2 mM glutamine-adapted cell line was directly transferred into glutamine-free medium and was able to grow at comparable rates without requiring further adaptation. Cells compensated the lack of glutamine by increasing their consumption of glutamate and aspartate.

Growth, metabolism and baculovirus production in suspension cultures of an Anticarsia gemmatalis cell line

The UFL-AG-286 cell line, established from embryonic tissue of the lepidopteran insect Anticarsia gemmatalis, has been identified as a good candidate to be used as a cellular substrate in the development of a process for in vitro production of the Anticarsia gemmatalis multicapsid nucleopolyhedrovirus, a baculovirus widely used as bioinsecticide. In order to characterize the technological properties of this cell line and evaluate its feasibility to use it for the large-scale production of Anticarsia gemmatalis multicapsid nucleopolyhedrovirus, UFL-AG-286 cells were adapted to grow as agitated suspension cultures in spinner-flasks. Batch suspension cultures of adapted cells in serum-supplemented TC-100 medium grew with a doubling time of about 29 h and reached a maximum cell density higher than 3.5 x 10(6) viable cells ml(-1). At the end of the growth period glucose was completely depleted from the culture medium, but L: -lactate was not produced. Amino acids, with the exception of glutamine, were only negligibly consumed or produced. In contrast to other insect cell lines, UFL-AG-286 cells appeared to be unable to synthesize alanine as a metabolic way to dispose the by-product ammonia. The synchronous infection of suspension cultures with Anticarsia gemmatalis multicapsid nucleopolyhedrovirus in the early to medium exponential growth phase yielded high amounts of both viral progenies per cell and reduced the specific demands of UFL-AG-286 cells for the main nutrients.

Biological Treatment of Cyanidation Waste Waters

An attached growth aerobic biological treatment process has been developed at Homestake Mining Co.’s Lead operation which not only oxidizes free and complexed cyanides, including the stable iron complexed cyanides, but also thiocyanate, and the oxidation byproduct ammonia. Through the employment of a mutant strain of bacteria which has been gradually and specifically acclimated to the waste, these potential pollutants are mineralized to relatively harmless sulfates, carbonates, and nitrates. The resultant effluent, through toxicological testing, has been shown compatible with the receiving stream, which serves as a cold water marginal trout fishery.

The Colony Shale Oil Project: ABSTRACT

For many years, the oil shale boom in western Colorado has been just around the corner. Now, the Colony Shale Oil Project, a joint development of The Oil Shale Corp. and Exxon Corp., is under full construction and will be the nation's first full-sized commercial shale oil project. The Colony operation, located in Garfield County in northwestern Colorado, is targeted for production at a rate of 47,000 bbl/day of synthetic oil in early 1986. To support the plant, it will be necessary to produce 66,000 tons/day of oil shale from a conventional room-and-pillar mine. The shale will be hauled from the mine in 85-ton trucks and crushed to -9 in. (229 mm) in a 72 × 109 in. (1.8 × 2.8 m) gyratory crusher. The coarse ore will then be transported by a 72 in. (1.8 m) conveyor belt 5,000 ft (1,525 m) to the secondary crushing station where it will be further reduced to -½ in. (13 mm) by eleven impactor crushers. The finely crushed shale will enter six Tosco II retorts, each capable of processing 11,000 tons/day. When heated to 900°F (482°C) in the pyrolysis drum, the kerogen vaporizes and is separated from the spent shale. The oil shale vapors are then condensed, fractionated, and upgraded by hydrotreating before entering a pipeline to be transported to a conventional refinery. By-products ammonia, sulfur, and coke will be recover d from the upgrading process. To mitigate the impact of a large work force on the sparsely populated Western Slope, Colony is developing the Battlement Mesa community on the Colorado River 15 mi (24 km) south of the project site. When completed, the community will house approximately 25,000 residents in a variety of housing types, and will be the second largest town in western Colorado. Colony is providing the equivalent of interest-free loans to local organizations for the establishment of schools, a fire station, and other needed facilities. End_of_Article - Last_Page 580------------