The Experts below are selected from a list of 9921 Experts worldwide ranked by ideXlab platform
Janet K. Jansson - One of the best experts on this subject based on the ideXlab platform.
-
novel 4 Chlorophenol degradation gene cluster and degradation route via hydroxyquinol in arthrobacter Chlorophenolicus a6
Applied and Environmental Microbiology, 2005Co-Authors: Maria Unell, Karolina Nordin, Janet K. JanssonAbstract:Arthrobacter Chlorophenolicus A6, a previously described 4-Chlorophenol-degrading strain, was found to degrade 4-Chlorophenol via hydroxyquinol, which is a novel route for aerobic microbial degradation of this compound. In addition, 10 open reading frames exhibiting sequence similarity to genes encoding enzymes involved in Chlorophenol degradation were cloned and designated part of a Chlorophenol degradation gene cluster (cph genes). Several of the open reading frames appeared to encode enzymes with similar functions; these open reading frames included two genes, cphA-I and cphA-II, which were shown to encode functional hydroxyquinol 1,2-dioxygenases. Disruption of the cphA-I gene yielded a mutant that exhibited negligible growth on 4-Chlorophenol, thereby linking the cph gene cluster to functional catabolism of 4-Chlorophenol in A. Chlorophenolicus A6. The presence of a resolvase pseudogene in the cph gene cluster together with analyses of the G+C content and codon bias of flanking genes suggested that horizontal gene transfer was involved in assembly of the gene cluster during evolution of the ability of the strain to grow on 4-Chlorophenol.
-
Degradation of 4-Chlorophenol at low temperature and during extreme temperature fluctuations by Arthrobacter Chlorophenolicus A6.
Microbial ecology, 2004Co-Authors: Agneta Backman, Janet K. JanssonAbstract:Low average temperatures and temperature fluctuations in temperate soils challenge the efficacy of microbial strains used for clean up of pollutants. In this study, we investigated the cold tolerance of Arthrobacter Chlorophenolicus A6, a microorganism previously shown to degrade high concentrations of 4-Chlorophenol at 28°C. Luciferase activity from a luc-tagged derivative of the strain (A6L) was used to monitor the metabolic status of the population during 4-Chlorophenol degradation. The A6L strain could degrade 200–300 μg mL−1 4-Chlorophenol in pure cultures incubated at 5°C, although rates of degradation, growth and the metabolic status of the cells were lower at 5°C compared to 28°C. When subjected to temperature fluctuations between 5 and 28°C, A6L continued to degrade 4-Chlorophenol and remained active. In soil microcosm experiments, the degradation rates were significantly faster the first week at 28°C, compared to 5°C. However, this difference was no longer seen after 7 days, and equally low 4-Chlorophenol concentrations were reached after 17 days at both temperatures. During 4-Chlorophenol degradation in soil, CFU and luciferase activity values remained constant at both 5 and 28°C. However, once most of the 4-Chlorophenol was degraded, both values decreased by 1–1.5 logarithmic values at 28°C, whereas they remained constant at 5°C, indicating a high survival of the cells at low temperatures. Because of the ability of A. Chlorophenolicus A6 to degrade high concentrations of 4-Chlorophenol at 5°C, together with its tolerance to temperature fluctuations and stress conditions found in soil, this strain is a promising candidate for bioaugmentation of Chlorophenol-contaminated soil in temperate climates.
-
impact of 4 Chlorophenol contamination and or inoculation with the 4 Chlorophenol degrading strain arthrobacter Chlorophenolicus a6l on soil bacterial community structure
FEMS Microbiology Ecology, 2002Co-Authors: Cecilia Jernberg, Janet K. JanssonAbstract:The 4-Chlorophenol-degrading strain, Arthrobacter Chlorophenolicus A6L (chromosomally tagged with the firefly luciferase gene, luc) was inoculated into 4-Chlorophenol-contaminated soil to assess the impact of bioaugmentation with a biodegrading strain on the indigenous microbiota. Simultaneously, the impact of 4-Chlorophenol alone, or inoculation with A. Chlorophenolicus into non-contaminated soil, was addressed. Using terminal restriction fragment length polymorphism (T-RFLP) several significant changes were detected in community fingerprint patterns obtained from soil microcosms treated under the different conditions. The relative abundances of some populations, as judged by the relative intensity of terminal restriction fragments, were significantly impacted by either 4-Chlorophenol, A. Chlorophenolicus inoculation, or by a combination of both inoculation and 4-Chlorophenol contamination. Some populations were significantly stimulated and others were significantly repressed when compared to control soil with no additions. For several peaks, the positive or negative impact imposed by the treatments increased over the 13-day incubation period. Some members of the bacterial community were specifically sensitive to A. Chlorophenolicus inoculation or to 4-Chlorophenol contamination, whereas other populations remained relatively unaffected by any of the treatments. The A. Chlorophenolicus inoculum was also monitored by T-RFLP and was found to have a significantly higher relative abundance in soil contaminated with 4-Chlorophenol. These results were substantiated by a high correlation to luciferase activity measurements and the number of colony forming units of the inoculum. Therefore, the A. Chlorophenolicus A6L population was positively stimulated by the presence of the 4-Chlorophenol substrate (180 μg g−1 soil) that it catabolized during the first 8 days of the incubation period as a carbon and energy source. Together, these results demonstrate that specific populations in the soil bacterial community rapidly fluctuated in response to specific disturbances and the resulting shifts in the community may therefore represent an adjustment in community structure favoring those populations best capable of responding to novel stress scenarios.
-
Impact of 4‐Chlorophenol contamination and/or inoculation with the 4‐Chlorophenol‐degrading strain, Arthrobacter Chlorophenolicus A6L, on soil bacterial community structure
FEMS microbiology ecology, 2002Co-Authors: Cecilia Jernberg, Janet K. JanssonAbstract:The 4-Chlorophenol-degrading strain, Arthrobacter Chlorophenolicus A6L (chromosomally tagged with the firefly luciferase gene, luc) was inoculated into 4-Chlorophenol-contaminated soil to assess the impact of bioaugmentation with a biodegrading strain on the indigenous microbiota. Simultaneously, the impact of 4-Chlorophenol alone, or inoculation with A. Chlorophenolicus into non-contaminated soil, was addressed. Using terminal restriction fragment length polymorphism (T-RFLP) several significant changes were detected in community fingerprint patterns obtained from soil microcosms treated under the different conditions. The relative abundances of some populations, as judged by the relative intensity of terminal restriction fragments, were significantly impacted by either 4-Chlorophenol, A. Chlorophenolicus inoculation, or by a combination of both inoculation and 4-Chlorophenol contamination. Some populations were significantly stimulated and others were significantly repressed when compared to control soil with no additions. For several peaks, the positive or negative impact imposed by the treatments increased over the 13-day incubation period. Some members of the bacterial community were specifically sensitive to A. Chlorophenolicus inoculation or to 4-Chlorophenol contamination, whereas other populations remained relatively unaffected by any of the treatments. The A. Chlorophenolicus inoculum was also monitored by T-RFLP and was found to have a significantly higher relative abundance in soil contaminated with 4-Chlorophenol. These results were substantiated by a high correlation to luciferase activity measurements and the number of colony forming units of the inoculum. Therefore, the A. Chlorophenolicus A6L population was positively stimulated by the presence of the 4-Chlorophenol substrate (180 μg g−1 soil) that it catabolized during the first 8 days of the incubation period as a carbon and energy source. Together, these results demonstrate that specific populations in the soil bacterial community rapidly fluctuated in response to specific disturbances and the resulting shifts in the community may therefore represent an adjustment in community structure favoring those populations best capable of responding to novel stress scenarios.
Cecilia Jernberg - One of the best experts on this subject based on the ideXlab platform.
-
impact of 4 Chlorophenol contamination and or inoculation with the 4 Chlorophenol degrading strain arthrobacter Chlorophenolicus a6l on soil bacterial community structure
FEMS Microbiology Ecology, 2002Co-Authors: Cecilia Jernberg, Janet K. JanssonAbstract:The 4-Chlorophenol-degrading strain, Arthrobacter Chlorophenolicus A6L (chromosomally tagged with the firefly luciferase gene, luc) was inoculated into 4-Chlorophenol-contaminated soil to assess the impact of bioaugmentation with a biodegrading strain on the indigenous microbiota. Simultaneously, the impact of 4-Chlorophenol alone, or inoculation with A. Chlorophenolicus into non-contaminated soil, was addressed. Using terminal restriction fragment length polymorphism (T-RFLP) several significant changes were detected in community fingerprint patterns obtained from soil microcosms treated under the different conditions. The relative abundances of some populations, as judged by the relative intensity of terminal restriction fragments, were significantly impacted by either 4-Chlorophenol, A. Chlorophenolicus inoculation, or by a combination of both inoculation and 4-Chlorophenol contamination. Some populations were significantly stimulated and others were significantly repressed when compared to control soil with no additions. For several peaks, the positive or negative impact imposed by the treatments increased over the 13-day incubation period. Some members of the bacterial community were specifically sensitive to A. Chlorophenolicus inoculation or to 4-Chlorophenol contamination, whereas other populations remained relatively unaffected by any of the treatments. The A. Chlorophenolicus inoculum was also monitored by T-RFLP and was found to have a significantly higher relative abundance in soil contaminated with 4-Chlorophenol. These results were substantiated by a high correlation to luciferase activity measurements and the number of colony forming units of the inoculum. Therefore, the A. Chlorophenolicus A6L population was positively stimulated by the presence of the 4-Chlorophenol substrate (180 μg g−1 soil) that it catabolized during the first 8 days of the incubation period as a carbon and energy source. Together, these results demonstrate that specific populations in the soil bacterial community rapidly fluctuated in response to specific disturbances and the resulting shifts in the community may therefore represent an adjustment in community structure favoring those populations best capable of responding to novel stress scenarios.
-
Impact of 4‐Chlorophenol contamination and/or inoculation with the 4‐Chlorophenol‐degrading strain, Arthrobacter Chlorophenolicus A6L, on soil bacterial community structure
FEMS microbiology ecology, 2002Co-Authors: Cecilia Jernberg, Janet K. JanssonAbstract:The 4-Chlorophenol-degrading strain, Arthrobacter Chlorophenolicus A6L (chromosomally tagged with the firefly luciferase gene, luc) was inoculated into 4-Chlorophenol-contaminated soil to assess the impact of bioaugmentation with a biodegrading strain on the indigenous microbiota. Simultaneously, the impact of 4-Chlorophenol alone, or inoculation with A. Chlorophenolicus into non-contaminated soil, was addressed. Using terminal restriction fragment length polymorphism (T-RFLP) several significant changes were detected in community fingerprint patterns obtained from soil microcosms treated under the different conditions. The relative abundances of some populations, as judged by the relative intensity of terminal restriction fragments, were significantly impacted by either 4-Chlorophenol, A. Chlorophenolicus inoculation, or by a combination of both inoculation and 4-Chlorophenol contamination. Some populations were significantly stimulated and others were significantly repressed when compared to control soil with no additions. For several peaks, the positive or negative impact imposed by the treatments increased over the 13-day incubation period. Some members of the bacterial community were specifically sensitive to A. Chlorophenolicus inoculation or to 4-Chlorophenol contamination, whereas other populations remained relatively unaffected by any of the treatments. The A. Chlorophenolicus inoculum was also monitored by T-RFLP and was found to have a significantly higher relative abundance in soil contaminated with 4-Chlorophenol. These results were substantiated by a high correlation to luciferase activity measurements and the number of colony forming units of the inoculum. Therefore, the A. Chlorophenolicus A6L population was positively stimulated by the presence of the 4-Chlorophenol substrate (180 μg g−1 soil) that it catabolized during the first 8 days of the incubation period as a carbon and energy source. Together, these results demonstrate that specific populations in the soil bacterial community rapidly fluctuated in response to specific disturbances and the resulting shifts in the community may therefore represent an adjustment in community structure favoring those populations best capable of responding to novel stress scenarios.
Ayse Kuleyin - One of the best experts on this subject based on the ideXlab platform.
-
removal of phenol and 4 Chlorophenol by surfactant modified natural zeolite
Journal of Hazardous Materials, 2007Co-Authors: Ayse KuleyinAbstract:In this study the adsorption characteristics of phenol and 4-Chlorophenol by surfactant-modified zeolite was investigated. Batch studies were performed to evaluate the effects of various experimental parameters such as contact time, adsorbent dose, initial concentration, and temperature on the removal of phenol and 4-Chlorophenol. The sorption kinetics was tested for intraparticle diffusion, Elovich, and pseudo-second order reaction and rate constants of kinetic models were calculated. Equilibrium isotherms for the adsorption of phenol were analyzed by Freundlich, Langmuir, and Tempkin isotherm models. Freundlich isotherm was found to best represent the data for phenol and 4-Chlorophenol adsorption.
Xihua Chen - One of the best experts on this subject based on the ideXlab platform.
-
Degradation of 4-Chlorophenol in a dielectric barrier discharge system
Separation and Purification Technology, 2013Co-Authors: Xihua Chen, Wenjuan Bian, Xuehong Song, Deqi Liu, Jiao ZhangAbstract:Abstract A dielectric barrier discharge system with a discharging zone apart from a degrading zone is developed to remove 4-Chlorophenol from water. Oxygen is fed through the discharging zone where it dissociates to form a plasma stream. The plasma stream is introduced into the degrading zone to make 4-Chlorophenol degraded effectively. The removal of 4-Chlorophenol was influenced by the processing parameters such as gas flow rate, pH and applied voltage. Increasing the peak voltage or gas flow rate among a certain range, the removal efficiency was enhanced. More than 80% of 4-Chlorophenol was removed in 6 min at pH 9.00, resulting in a high energy efficiency of 46.34 × 10 −9 mol J −1 (21.46 g/kW h). Discharging in initial 4-Chlorophenol solution, the removal percent was about 90% at 30 min with peak voltage of 14.64 kV and oxygen flow rate of 200 L h −1 . The corresponding energy efficiency was 12.35 × 10 −9 mol J −1 (5.72 g/kW h). During the degradation, aromatic products and organic acids were produced. The main aromatic intermediates were different at different pH, suggesting different pathways of the target contaminant. After the benzene ring was opened, organic acid such as formic acid, oxalic acid, d -(+)-malic acid and maleic acid were formed.
-
The intermediate products in the degradation of 4-Chlorophenol by pulsed high voltage discharge in water.
Journal of hazardous materials, 2011Co-Authors: Wenjuan Bian, Xuehong Song, Deqi Liu, Jiao Zhang, Xihua ChenAbstract:Abstract Degradation of 4-Chlorophenol by pulsed high voltage discharge is an intricate process involving a series of complex chemical reactions. Hydroxylation of 4-Chlorophenol to form hydroquinone, 4-chlororesorcinol and 4-chlorocatechol is the first step, though a very small amount of direct cleavage products of the C1–C2 or C5–C6 bond are observed. The yield of 4-chlorocatechol is about twice as much as that of hydroquinone. Less 4-chloresorcinol is produced. The free chloride ions dropped from the 4-Chlorophenol degradation can obtain reactivity again from the discharge, and react with undegraded 4-Chlorophenol to form 2,4-diChlorophenol. Some ring-opened products have also been identified and their possible reaction routes are proposed. Several compounds are verified by use of authentic samples. The more stable ring-opened products are low molecular weight (LMW) acids such as formic, acetic, oxalic, malonate, maleic and malic acid. By discharging 4-Chlorophenol aqueous solution for 36 min, the amount of carbons obtained from organic acids is more than 50% while that of carbons from aromatic products less than 20% in the carbons of degraded 4-Chlorophenol, which is about 94% of initial carbons. After 60 min of discharge, all the 4-Chlorophenol and its aromatic intermediates have been removed completely and the organic carbons are mainly presented as organic acid such as acetic and oxalate acid. At the end of the 120 min discharge, the amount of the remaining organic carbons is not more than 14% of the initial carbons.
Juan J Rodriguez - One of the best experts on this subject based on the ideXlab platform.
-
Kinetics of 4-Chlorophenol Hydrodechlorination with Alumina and Activated Carbon-Supported Pd and Rh Catalysts
Industrial & Engineering Chemistry Research, 2009Co-Authors: Elena Díaz, Angel F. Mohedano, Miguel A. Gilarranz, L. Calvo, José A. Casas, Juan J RodriguezAbstract:The hydrodechlorination of 4-Chlorophenol promoted by different commercial catalysts based on Pd and Rh on γ-alumina and activated carbon has been investigated in a continuous stirred basket reactor (20−40 °C and 1 bar) in order to analyze the kinetics of the reaction. External and internal mass transfer effects were found to be negligible from the values of the Carberry and Weisz−Prater numbers. The reaction rate showed a first-order dependence with respect to 4-Chlorophenol. All catalysts were effective in the removal of 4-Chlorophenol, with phenol, cyclohexanone, and cyclohexanol identified as reaction products, although the last one was only detected with the Rh/AC catalyst. The highest apparent kinetic constant values correspond to the hydrogenation of 4-Chlorophenol to phenol. These values were in the range 146−478 L/kgcat·h for Pd/Al2O3, 179−713 L/kgcat·h for Pd/AC, and 44−172 L/kgcat·h for Rh/AC. The values of the apparent activation energy for 4-Chlorophenol disappearance ranged within 47−58 kJ/mol.
-
kinetics of the hydrodechlorination of 4 Chlorophenol in water using pd pt and rh al2o3 catalysts
Industrial & Engineering Chemistry Research, 2008Co-Authors: Elena Díaz, Angel F. Mohedano, Miguel A. Gilarranz, L. Calvo, José A. Casas, Juan J RodriguezAbstract:The hydrodechlorination of 4-Chlorophenol in an aqueous phase was studied in a semicontinuous basket stirred tank reactor using Pd, Pt, and Rh on γ-alumina commercial catalysts (0.5% w/w) under mild reaction conditions. The catalytic activity was studied in the temperature range of 20−40 °C. Pd and Rh showed a higher catalytic activity than Pt. From consumption of 4-Chlorophenol and evolution of the reaction products, phenol, cyclohexanone, and cyclohexanol, a reaction scheme based on a parallel-series pathway and a kinetic model based on pseudo-first-order dependence on 4-Chlorophenol have been proposed. Hydrodechlorination of 4-Chlorophenol to phenol exhibits the largest apparent kinetic constant for Pd (k1 = 0.42–0.73 h−1) and Pt (k1 = 0.20–0.42 h−1) catalysts, while in the case of Rh, the three reactions, hydrodechlorination of 4-Chlorophenol to phenol (k1 = 0.43–0.64 h−1) and hydrogenation of phenol to cyclohexanone (k3 = 0.42–0.78 h−1) and to cyclohexanol (k4 = 0.38–0.65 h−1), have comparable values...
