The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Guo-liang Zhang - One of the best experts on this subject based on the ideXlab platform.
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Solubility of sodium 4-Nitrotoluene-2-sulfonate in (propanol + water) and (ethylene glycol + water) systems
The Journal of Chemical Thermodynamics, 2020Co-Authors: Ling-xin Wang, Fengbao Zhang, Xiao-man Yu, Guo-liang ZhangAbstract:Abstract The solubility data of sodium 4-Nitrotoluene-2-sulfonate (NTSNa) in aqueous organic solutions (propanol + water) and (ethylene glycol + water) were measured at temperatures ranging from (290 to 351) K using a dynamic method. The mole fraction of water in solvent mixtures ranged from 0 to 0.8. The solubility values are correlated with the electrolyte non-random two-liquid (E-NRTL) model. From the results obtained, the E-NRTL model provides a satisfactory mathematical representation of the experimental results for the (NTSNa + propanol + water) system and an unsatisfactory result for the (NTSNa + ethylene glycol + water) system. Thus, the modified Apelblat model is applied to describe the (NTSNa + ethylene glycol + water) system also. The calculated (solid + liquid) equilibrium temperatures with the modified Apelblat model are in good agreement with the experimental results. The root-mean-square deviations of solubility temperature varied from (0.08 to 0.94) K for two models. The effect of different aqueous organic solutions on the reaction of oxidation 4-Nitrotoluene-2-sulfonic acid (NTS) to 4,4′-dinitrostilbene-2,2′-disulfonic acid (DNS) was discussed.
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Solubility of disodium 4,4′-dinitrostilbene-2,2′-disulfonate and sodium 4-Nitrotoluene-2-sulfonate in aqueous organic solutions and its application feasibility in oxidation stage of DSD acid synthesis
The Journal of Chemical Thermodynamics, 2014Co-Authors: Wen Zhao, Fengbao Zhang, Guo-liang ZhangAbstract:Abstract Solid–liquid equilibrium (SLE) measurements for disodium 4,4′-dinitrostilbene-2,2′-disulfonate (DNSNa) and sodium 4-Nitrotoluene-2-sulfonate (NTSNa) in aqueous ethylene glycol monoethyl ether solution and aqueous ethylene glycol monobutyl ether solution were conducted using a dynamic method over the temperature range from (280 to 335) K. A synergistic effect on DNSNa solubility was observed with the maximum solubility at solute-free mass fraction of ethylene glycol monoethyl ether w 3 0 = 0.4000 and solute-free mass fraction of ethylene glycol monobutyl ether w 4 0 = 0.5999 , respectively. The solubility data were correlated using the thermodynamic electrolyte non-random two-liquid (E-NRTL) model and model parameters were determined simultaneously. Aqueous ethylene glycol monobutyl ether solution at solute-free mass fraction of ethylene glycol monobutyl ether w 4 0 = 0.2000 was found to be suitable solvent medium for the oxidation of 4-Nitrotoluene-2-sulfonic acid (NTS) to 4,4′-dinitrostilbene-2,2′-disulfonic acid (DNS) and the conclusion was confirmed using the static analytical method combined with UV–VIS spectrophotometer.
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Investigation the solubility difference of sodium 4-Nitrotoluene-2-sulfonate and 4-Nitrotoluene-2-sulfonic acid in (sulfuric acid + water) system
Fluid Phase Equilibria, 2013Co-Authors: Ying Yang, Hui Zhang, Fengbao Zhang, Guo-liang ZhangAbstract:Abstract The solubility data of sodium 4-Nitrotoluene-2-sulfonate (NTSNa) and 4-Nitrotoluene-2-sulfonic acid (NTS) in (sulfuric acid + water) mixture solvents were measured at temperatures ranging from 285 K to 340 K using a dynamic method. The solute-free mass fraction of sulfuric acid ( w 3 0 ) in solvent mixtures ranged from 0 to 0.70. NTS showed the lowest solubility when w 3 0 is 0.60. After the sulfonation reaction, the reaction solution should be diluted to the concentration 0.60 mass fraction of sulfuric acid to make NTS precipitate as much as possible. Solubility of NTS is much larger than that of NTSNa when w 3 0 is smaller than 0.20, but no obvious solubility difference can be detected when w 3 0 is larger than 0.50. This result shows that only when w 3 0 is smaller than 0.20, the recycle process which was designed by our previous study can be carried out. The solubility data were correlated by the modified Apelblat model, the calculated (solid + liquid) equilibrium curves are in good agreement with the experimental data.
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Investigation of sodium 4-Nitrotoluene-2-sulfonate solubility in aqueous organic solutions
The Journal of Chemical Thermodynamics, 2011Co-Authors: Ling-xin Wang, Fengbao Zhang, Xiao-man Yu, Guo-liang ZhangAbstract:Abstract The solubility of sodium 4-Nitrotoluene-2-sulfonate (NTSNa) in binary solvent mixtures (methanol + water), (ethanol + water), and (2-methoxyethanol + water) was investigated over the temperature range from (288 to 344) K. The mole fraction of water in solvent mixtures ranged from 0 to 0.8. The solubility data are described by the electrolyte non-random two-liquid (E-NRTL) model. The E-NRTL binary interaction parameters are expressed as a function of temperature, and were obtained from the experimental data. The root-mean-square deviations of solubility temperature varied from (0.20 to 1.35) K.
Gautam Sarath - One of the best experts on this subject based on the ideXlab platform.
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TNT Biotransformation and Detoxification by a Pseudomonas Aeruginosa Strain
Biodegradation, 2003Co-Authors: Byung-taek Oh, Patrick J. Shea, Rhae A. Drijber, Galina K. Vasilyeva, Gautam SarathAbstract:Successful microbial-mediated remediation requires transformationpathways that maximize metabolism and minimize the accumulation of toxic products. Pseudomonas aeruginosa strain MX, isolated from munitions-contaminated soil, degraded 100 mg TNT L^-1 in culture medium within 10 h under aerobic conditions. The major TNT products were 2-amino-4,6-dinitrotoluene (2ADNT, primarily in the supernatant) and 2,2'-azoxytoluene (2,2'AZT, primarily in the cell fraction), which accumulated as major products via the intermediate2-hydroxylamino-4,6-dinitrotoluene (2HADNT). The 2HADNT and2,2'AZT were relatively less toxic to the strain than TNT and 2ADNT. Aminodinitrotoluene (ADNT) production increased when yeast extract was added to the medium. While TNT transformation rate was not affected by pH, more HADNTs accumulated at pH 5.0 than at pH 8.0 and AZTs did not accumulate at the lower pH. The appearance of 2,6-diamino-4-Nitrotoluene (2,6DANT) and 2,4-diamino-6-nitrotoluene (2,4DANT); dinitrotoluene (DNT) and nitrotoluene (NT); and 3,5-dinitroaniline (3,5DNA) indicated various routes of TNT metabolism and detoxification by P. aeruginosa strain MX.
Rebecca E. Parales - One of the best experts on this subject based on the ideXlab platform.
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Nitrobenzoates and Aminobenzoates Are Chemoattractants for Pseudomonas Strains
Applied and Environmental Microbiology, 2020Co-Authors: Rebecca E. ParalesAbstract:Three Pseudomonas strains were tested for the ability to sense and respond to nitrobenzoate and aminobenzoate isomers in chemotaxis assays. Pseudomonas putida PRS2000, a strain that grows on benzoate and 4-hydroxybenzoate by using the β-ketoadipate pathway, has a well-characterized β-ketoadipate-inducible chemotactic response to aromatic acids. PRS2000 was chemotactic to 3- and 4-nitrobenzoate and all three isomers of aminobenzoate when grown under conditions that induce the benzoate chemotactic response. P. putida TW3 and Pseudomonas sp. strain 4NT grow on 4-Nitrotoluene and 4-nitrobenzoate by using the ortho (β-ketoadipate) and meta pathways, respectively, to complete the degradation of protocatechuate derived from 4-Nitrotoluene and 4-nitrobenzoate. However, based on results of catechol 1,2-dioxygenase and catechol 2,3-dioxygenase assays, both strains were found to use the β-ketoadipate pathway for the degradation of benzoate. Both strains were chemotactic to benzoate, 3- and 4-nitrobenzoate, and all three aminobenzoate isomers after growth with benzoate but not succinate. Strain TW3 was chemotactic to the same set of aromatic compounds after growth with 4-Nitrotoluene or 4-nitrobenzoate. In contrast, strain 4NT did not respond to any aromatic acids when grown with 4-Nitrotoluene or 4-nitrobenzoate, apparently because these substrates are not metabolized to the inducer (β-ketoadipate) of the chemotaxis system. The results suggest that strains TW3 and 4NT have a β-ketoadipate-inducible chemotaxis system that responds to a wide range of aromatic acids and is quite similar to that present in PRS2000. The broad specificity of this chemotaxis system works as an advantage in strains TW3 and 4NT because it functions to detect diverse carbon sources, including 4-nitrobenzoate.
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Evolution of a new bacterial pathway for 4-Nitrotoluene degradation
Molecular Microbiology, 2011Co-Authors: Rebecca E. ParalesAbstract:Summary Bacteria that assimilate synthetic nitroarene compounds represent unique evolutionary models, as their metabolic pathways are in the process of adaptation and optimization for the consumption of these toxic chemicals. We used Acidovorax sp. strain JS42, which is capable of growth on nitrobenzene and 2-nitrotoluene, in experiments to examine how a nitroarene degradation pathway evolves when its host strain is challenged with direct selective pressure to assimilate non-native substrates. Although the same enzyme that initiates the degradation of nitrobenzene and 2-nitrotoluene also oxidizes 4-Nitrotoluene to 4-methylcatechol, which is a growth substrate for JS42, the strain is incapable of growth on 4-Nitrotoluene. Using long-term laboratory evolution experiments, we obtained JS42 mutants that gained the ability to grow on 4-Nitrotoluene via a new degradation pathway. The underlying basis for this new activity resulted from the accumulation of specific mutations in the gene encoding the dioxygenase that catalyses the initial oxidation of nitroarene substrates, but at positions distal to the active site and previously unknown to affect activity in this or related enzymes. We constructed additional mutant dioxygenases to identify the order of mutations that led to the improved enzymes. Biochemical analyses revealed a defined, step-wise pathway for the evolution of the improved dioxygenases.
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Active site residues controlling substrate specificity in 2-nitrotoluene dioxygenase from Acidovorax sp. strain JS42
Journal of Industrial Microbiology and Biotechnology, 2005Co-Authors: Juanito V. Parales, Rosmarie Friemann, Rebecca E. ParalesAbstract:Acidovorax (formerly Pseudomonas ) sp. strain JS42 utilizes 2-nitrotoluene as sole carbon, nitrogen, and energy source. 2-Nitrotoluene 2,3-dioxygenase (2NTDO) catalyzes the initial step in 2-nitrotoluene degradation by converting 2-nitrotoluene to 3-methylcatechol. In this study, we identified specific amino acids at the active site that control specificity. The residue at position 350 was found to be critical in determining both the enantiospecificity of 2NTDO with naphthalene and the ability to oxidize the ring of mononitrotoluenes. Substitution of Ile350 by phenylalanine resulted in an enzyme that produced 97% (+)-(1 R , 2 S )- cis -naphthalene dihydrodiol, in contrast to the wild type, which produced 72% (+)-(1 R , 2 S )- cis -naphthalene dihydrodiol. This substitution also severely reduced the ability of the enzyme to produce methylcatechols from nitrotoluenes. Instead, the methyl group of each nitrotoluene isomer was preferentially oxidized to form the corresponding nitrobenzyl alcohol. Substitution of a valine at position 258 significantly changed the enantiospecificity of 2NTDO (54% (−)-(1 S , 2 R )- cis -naphthalene dihydrodiol formed from naphthalene) and the ability of the enzyme to oxidize the aromatic ring of nitrotoluenes. Based on active site modeling using the crystal structure of nitrobenzene 1,2 dioxygenase from Comamonas sp. JS765, Asn258 appears to contribute to substrate specificity through hydrogen bonding to the nitro group of nitrotoluenes.
Mohe Zhang - One of the best experts on this subject based on the ideXlab platform.
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degradation of 2 4 6 trinitrotoluene tnt by immobilized microorganism biological filter
Process Biochemistry, 2010Co-Authors: Zhongyou Wang, Zhengfang Ye, Mohe ZhangAbstract:Abstract The combined process of immobilized microorganism-biological filter was used to degrade TNT in an aqueous solution. The results showed that the process could effectively degrade TNT, which was not detected in the effluent of the system. GC/MS analysis identified 2-amino-4,6-dinitrotoluene (2-A-4,6-DNT), 4-amino-2,6-dinitrotoluene (4-A-2,6-DNT), 2,4-diamino-6-nitrotoluene (2,4-DA-6-NT) and 2,4-diamino-6-nitrotoluene (2,6-DA-4-NT) as the main anaerobic degradation products. In addition, the Haldane model successfully described the anaerobic degradation of TNT with high correlation coefficients (R2 = 0.9803). As the electron donor, ethanol played a major role in the TNT biodegradation. More than twice the theoretical requirement of ethanol was necessary to achieve a high TNT degradation rate (above 97.5%). Moreover, Environment Scan Electron Microscope (ESEM) analysis revealed that a large number of globular microorganisms were successfully immobilized on the surface of the carrier. Further analysis by Polymerase Chain Reaction (PCR)-Denaturing Gradient Gel Electrophoresis (DGGE) demonstrated that the special bacterial for TNT degradation may have generated during the domestication with TNT for 150 days. The dominant species for TNT degradation were identified by comparing gene sequences with Genebank.
Byung-taek Oh - One of the best experts on this subject based on the ideXlab platform.
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TNT Biotransformation and Detoxification by a Pseudomonas Aeruginosa Strain
Biodegradation, 2003Co-Authors: Byung-taek Oh, Patrick J. Shea, Rhae A. Drijber, Galina K. Vasilyeva, Gautam SarathAbstract:Successful microbial-mediated remediation requires transformationpathways that maximize metabolism and minimize the accumulation of toxic products. Pseudomonas aeruginosa strain MX, isolated from munitions-contaminated soil, degraded 100 mg TNT L^-1 in culture medium within 10 h under aerobic conditions. The major TNT products were 2-amino-4,6-dinitrotoluene (2ADNT, primarily in the supernatant) and 2,2'-azoxytoluene (2,2'AZT, primarily in the cell fraction), which accumulated as major products via the intermediate2-hydroxylamino-4,6-dinitrotoluene (2HADNT). The 2HADNT and2,2'AZT were relatively less toxic to the strain than TNT and 2ADNT. Aminodinitrotoluene (ADNT) production increased when yeast extract was added to the medium. While TNT transformation rate was not affected by pH, more HADNTs accumulated at pH 5.0 than at pH 8.0 and AZTs did not accumulate at the lower pH. The appearance of 2,6-diamino-4-Nitrotoluene (2,6DANT) and 2,4-diamino-6-nitrotoluene (2,4DANT); dinitrotoluene (DNT) and nitrotoluene (NT); and 3,5-dinitroaniline (3,5DNA) indicated various routes of TNT metabolism and detoxification by P. aeruginosa strain MX.
