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Jalal Hawari - One of the best experts on this subject based on the ideXlab platform.
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metabolism of hexahydro 1 3 5 trinitro 1 3 5 triazine through initial reduction to hexahydro 1 nitroso 3 5 dinitro 1 3 5 triazine followed by denitration in Clostridium bifermentans haw 1
Applied Microbiology and Biotechnology, 2003Co-Authors: Jianshen Zhao, Louise Paquet, Annamaria Halasz, Jalal HawariAbstract:A fast hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)-degrading [28.1 μmol h−1 g (dry weight) cells−1; biomass, 0.16 g (dry weight) cells−1] and strictly anaerobic bacterial strain, HAW-1, was isolated and identified as Clostridium bifermentans using a 16S-rRNA-based method. Based on initial rates, strain HAW-1 transformed RDX to hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX), hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine (DNX), and hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX) with yields of 56, 7.3 and 0.2%, respectively. Complete removal of RDX and its nitroso metabolites produced (%, of total C or N) methanol (MeOH, 23%), formaldehyde (HCHO, 7.4%), carbon dioxide (CO2, 3.0%) and nitrous oxide (N2O, 29.5%) as end products. Under the same conditions, strain HAW-1 transformed MNX separately at a rate of 16.9 μmol h−1 g (dry weight) cells−1 and produced DNX (25%) and TNX (0.4%) as transient products. Final MNX transformation products were (%, of total C or N) MeOH (21%), HCHO (2.9%), and N2O (17%). Likewise strain HAW-1 degraded TNX at a rate of 7.5 μmol h−1 g (dry weight) cells−1 to MeOH and HCHO. Furthermore, removal of both RDX and MNX produced nitrite (NO2 −) as a transient product, but the nitrite release rate from MNX was quicker than from RDX. Thus, the predominant pathway for RDX degradation is based on initial reduction to MNX followed by denitration and decomposition. The continued sequential reduction to DNX and TNX is only a minor route.
Kazuhiro Takamizawa - One of the best experts on this subject based on the ideXlab platform.
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resolution of culture Clostridium bifermentans dph 1 into two populations a Clostridium sp and tetrachloroethene dechlorinating desulfitobacterium hafniense strain jh1
Applied and Environmental Microbiology, 2008Co-Authors: Kelly E Fletcher, Kirsti M Ritalahti, Kurt D Pennell, Kazuhiro TakamizawaAbstract:Clostridium bifermentans strain DPH-1 reportedly dechlorinates tetrachloroethene (PCE) to cis-1,2-dichloroethene. Cultivation-based approaches resolved the DPH-1 culture into two populations: a nondechlorinating Clostridium sp. and PCE-dechlorinating Desulfitobacterium hafniense strain JH1. Strain JH1 carries pceA, encoding a PCE reductive dehalogenase, and shares other characteristics with Desulfitobacterium hafniense strain Y51.
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complete dechlorination of tetrachloroethylene by use of an anaerobic Clostridium bifermentans dph 1 and zero valent iron
Environmental Technology, 2008Co-Authors: Youngcheol Chang, Takeshi Sato, S Kikuchi, N Kawauchi, Kazuhiro TakamizawaAbstract:Abstract A laboratory test was conducted to examine the combined effect of an anaerobic Clostridium bifermentans DPH‐1 and addition of zero‐valent iron (Fe0) on the reductive dechlorination of tetrachloroethylene (PCE). In addition, the dechlorination of cis‐1,2‐dichloroethylene (cDCE) produced from PCE was examined using Fe0. The cDCE produced was completely dechlorinated to non‐toxic end products, mostly, ethylene by a subsequent chemical reductive process. Production of ethylene was dramatically increased with increase of initial cDCE concentration in the range of 10.3 µM to 928 µM (1.0–90 mg l−1) and the velocity constant was calculated to be 0.38 day−1. On the other hand, the combined use of strain DPH‐1 and Fe0 showed the most significant effect on the initial PCE dechlorination, but cohesion of Fe0 was found to inhibit the dechlorination rate of PCE. It is thought that phosphoric acid iron contained in a medium forms film on the surface of iron particle, so oxidation of iron is inhibited.
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in vitro dehalogenation of tetrachloroethylene pce by cell free extracts of Clostridium bifermentans dph 1
Bioresource Technology, 2001Co-Authors: Youngcheol Chang, Masahiro Hatsu, Benedict C Okeke, Kazuhiro TakamizawaAbstract:Cell-free extracts of Clostridium bifermentans DPH-1 catalyzed tetrachloroethylene (PCE) dechlorination. PCE degradation was stimulated by addition of a variety of electron donors. Ethanol (0.61 mM) was the most effective electron donor for PCE dechlorination. Maximum activity was recorded at 30 degrees C and pH 7.5. Addition of NADH as a cofactor stimulated enzymatic activity but the activity was not stimulated by addition of metal ions. When the cell-free enzyme extract was incubated in the presence of titanium citrate as a reducing agent, the dehalogenase was rapidly inactivated by propyl iodide (0.5 mM). The activity of propyliodide-reacted enzyme was restored by illumination with a 250 W lamp. The dehalogenase activity was also inhibited by cyanide. The substrate spectrum of activity included trichloroethylene (TCE), cis-1,2-dichloroethylene (cDCE), trans-dichloroethylene, 1,1-dichloroethylene, 1,2-dichloroethane, and 1,1,2-trichloroethane. The highest rate of degradation of the chlorinated aliphatic compounds was achieved with PCE, and PCE was principally degraded via TCE to cDCE. Results indicate that the dehalogenase could play a vital role in the breakdown of PCE as well as a variety of other chlorinated aliphatic compounds.
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purification cloning and sequencing of an enzyme mediating the reductive dechlorination of tetrachloroethylene pce from Clostridium bifermentans dph 1
Canadian Journal of Microbiology, 2001Co-Authors: Benedict C Okeke, Young C Chang, Masahiro Hatsu, Tohru Suzuki, Kazuhiro TakamizawaAbstract:An enzyme mediating the reductive dechlorination of tetrachloroethylene (PCE) from cell-free extracts of Clostridium bifermentans DPH-1 was purified, cloned, and sequenced. The enzyme catalyzed the...
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removal of tetrachloroethylene in an anaerobic fixed bed reactor immobilized with Clostridium bifermentans dph 1
Water supply, 2001Co-Authors: Youngcheol Chang, Masahiro Hatsu, K Asanuma, Kazuhiro TakamizawaAbstract:An upflow fixed-bed reactor was evaluated for the removal of tetrachloroethylene (PCE) by a strictly anaerobic, PCE dechlorinating bacterium, Clostridium bifermentans DPH-1 immobilized on sterile ceramic beads. The ceramic beads provide a large surface area for development of cell mass in the column. For kinetic experiments, the conventional first-order reaction kinetics was applied to evaluate the batch and continuous immobilized reactors. Velocity constants ( K B and K C ) under the batch culture and continuous culture were determined to be 1.9 × 10 –2 (mg protein –1 h –1 ) and 1.4 × 10 –2 (mg protein –1 h –1 ), respectively. Maximum specific degradation rate of PCE was calculated as 0.16 (10 –3 μmol mg protein –1 h –1 from average influent concentration of PCE (12 μM) in the bioreactor. Simultaneously maximum volumetric degradation rate was also computed as 10.2 μmol l –1 h –1 . The volumetric degradation rate was relatively higher than those of other reactors. In order to maintain the efficiency of PCE dechlorination, 20 h or more HRT in the reactor system was required.
Jianshen Zhao - One of the best experts on this subject based on the ideXlab platform.
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metabolism of hexahydro 1 3 5 trinitro 1 3 5 triazine through initial reduction to hexahydro 1 nitroso 3 5 dinitro 1 3 5 triazine followed by denitration in Clostridium bifermentans haw 1
Applied Microbiology and Biotechnology, 2003Co-Authors: Jianshen Zhao, Louise Paquet, Annamaria Halasz, Jalal HawariAbstract:A fast hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)-degrading [28.1 μmol h−1 g (dry weight) cells−1; biomass, 0.16 g (dry weight) cells−1] and strictly anaerobic bacterial strain, HAW-1, was isolated and identified as Clostridium bifermentans using a 16S-rRNA-based method. Based on initial rates, strain HAW-1 transformed RDX to hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX), hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine (DNX), and hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX) with yields of 56, 7.3 and 0.2%, respectively. Complete removal of RDX and its nitroso metabolites produced (%, of total C or N) methanol (MeOH, 23%), formaldehyde (HCHO, 7.4%), carbon dioxide (CO2, 3.0%) and nitrous oxide (N2O, 29.5%) as end products. Under the same conditions, strain HAW-1 transformed MNX separately at a rate of 16.9 μmol h−1 g (dry weight) cells−1 and produced DNX (25%) and TNX (0.4%) as transient products. Final MNX transformation products were (%, of total C or N) MeOH (21%), HCHO (2.9%), and N2O (17%). Likewise strain HAW-1 degraded TNX at a rate of 7.5 μmol h−1 g (dry weight) cells−1 to MeOH and HCHO. Furthermore, removal of both RDX and MNX produced nitrite (NO2 −) as a transient product, but the nitrite release rate from MNX was quicker than from RDX. Thus, the predominant pathway for RDX degradation is based on initial reduction to MNX followed by denitration and decomposition. The continued sequential reduction to DNX and TNX is only a minor route.
R L Crawford - One of the best experts on this subject based on the ideXlab platform.
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Degradation of 2-sec-butyl-4,6-dinitrophenol (dinoseb) by Clostridium bifermentans KMR-1.
Applied and environmental microbiology, 1996Co-Authors: T B Hammill, R L CrawfordAbstract:A strain of Clostridium bifermentans, KMR-1, degraded 2-sec-butyl-4,6-dinitrophenol (dinoseb) to a level below the limit of detection by high-performance liquid chromatography (0.5 mg/liter) within 96 h, with no accumulation of aromatic intermediates. KMR-1 could not utilize dinoseb as a sole carbon or energy source, and degradation occurred via cometabolism in the presence of a fermentable carbon source. KMR-1 mineralized some dinoseb in anaerobic cultures, evolving 7.2% of the radioactive label in U-ring 14C-labeled dinoseb as 14CO2. The remaining anaerobic degradation products were incubated with aerobic soil bacteria, and 35.4% of this residual radioactive label was evolved as 14CO2. During this mineralization experiment, 38.9% of the initial label was evolved as 14CO2 after both anaerobic and aerobic phases. This is the first demonstration of dinoseb degradation by a pure microbial culture.
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biotransformation of the explosives 2 4 6 trinitrotoluene and 1 3 5 triaza 1 3 5 trinitrocyclohexane by Clostridium bifermentans
1994Co-Authors: K M Regan, R L CrawfordAbstract:A strain of Clostridium bifermentans isolated from a munitions-supplemented enrichment was able to remove both TNT (2,4,6-trinitrotoluene) and RDX (1,3,5-triaza 1,3,5-trinitrocyclohexane) from its growth media. Biotransformations of TNT and RDX by cometabolism in a nutrient rich medium reduced the removal time from several days to a few hours, as compared to a nutrient limited medium. Redox potential (Eh) of the media had important effects on the biological and abiological transformations of the munition compounds.
Annamaria Halasz - One of the best experts on this subject based on the ideXlab platform.
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metabolism of hexahydro 1 3 5 trinitro 1 3 5 triazine through initial reduction to hexahydro 1 nitroso 3 5 dinitro 1 3 5 triazine followed by denitration in Clostridium bifermentans haw 1
Applied Microbiology and Biotechnology, 2003Co-Authors: Jianshen Zhao, Louise Paquet, Annamaria Halasz, Jalal HawariAbstract:A fast hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX)-degrading [28.1 μmol h−1 g (dry weight) cells−1; biomass, 0.16 g (dry weight) cells−1] and strictly anaerobic bacterial strain, HAW-1, was isolated and identified as Clostridium bifermentans using a 16S-rRNA-based method. Based on initial rates, strain HAW-1 transformed RDX to hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX), hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine (DNX), and hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX) with yields of 56, 7.3 and 0.2%, respectively. Complete removal of RDX and its nitroso metabolites produced (%, of total C or N) methanol (MeOH, 23%), formaldehyde (HCHO, 7.4%), carbon dioxide (CO2, 3.0%) and nitrous oxide (N2O, 29.5%) as end products. Under the same conditions, strain HAW-1 transformed MNX separately at a rate of 16.9 μmol h−1 g (dry weight) cells−1 and produced DNX (25%) and TNX (0.4%) as transient products. Final MNX transformation products were (%, of total C or N) MeOH (21%), HCHO (2.9%), and N2O (17%). Likewise strain HAW-1 degraded TNX at a rate of 7.5 μmol h−1 g (dry weight) cells−1 to MeOH and HCHO. Furthermore, removal of both RDX and MNX produced nitrite (NO2 −) as a transient product, but the nitrite release rate from MNX was quicker than from RDX. Thus, the predominant pathway for RDX degradation is based on initial reduction to MNX followed by denitration and decomposition. The continued sequential reduction to DNX and TNX is only a minor route.