Characterization of naphthalene degradation by Streptomyces sp. QWE-5 isolated from active sludge

2014 ◽  
Vol 70 (6) ◽  
pp. 1129-1134 ◽  
Author(s):  
Peng Xu ◽  
Wencheng Ma ◽  
Hongjun Han ◽  
Baolin Hou ◽  
Shengyong Jia
Keyword(s):  
Degradation Rate ◽  
Substrate Inhibition ◽  
Degradation Pathway ◽  
Active Sludge ◽  
Streptomyces Sp ◽  
Metabolic Intermediates ◽  
Naphthalene Degradation ◽  
Specific Degradation ◽  
Kinetics Of

A bacterial strain, QWE-5, which utilized naphthalene as its sole carbon and energy source, was isolated and identified as Streptomyces sp. It was a Gram-positive, spore-forming bacterium with a flagellum, with whole, smooth, convex and wet colonies. The optimal temperature and pH for QWE-5 were 35 °C and 7.0, respectively. The QWE-5 strain was capable of completely degrading naphthalene at a concentration as high as 100 mg/L. At initial naphthalene concentrations of 10, 20, 50, 80 and 100 mg/L, complete degradation was achieved within 32, 56, 96, 120 and 144 h, respectively. Kinetics of naphthalene degradation was described using the Andrews equation. The kinetic parameters were as follows: qmax (maximum specific degradation rate) = 1.56 h−1, Ks (half-rate constant) = 60.34 mg/L, and KI (substrate-inhibition constant) = 81.76 mg/L. Metabolic intermediates were identified by gas chromatography and mass spectrometry, allowing a new degradation pathway for naphthalene to be proposed. In this pathway, monooxygenation of naphthalene yielded naphthalen-1-ol. Further degradation by Streptomyces sp. QWE-5 produced acetophenone, followed by adipic acid, which was produced as a combination of decarboxylation and hydroxylation processes.

scholarly journals Structural characterization of Polycyclic Aromatic Hydrocarbon degrading enzymes

2014 ◽  
Vol 70 (a1) ◽  
pp. C472-C472
Author(s):  
Juliana Coitinho ◽  
Debora Costa ◽  
Samuel Guimaraes ◽  
Cintia Neves ◽  
Simara Araujo ◽  
...  
Keyword(s):  
Aromatic Hydrocarbons ◽  
Environmental Protection Agency ◽  
Metabolic Activation ◽  
Degradation Pathway ◽  
Laboratory Animals ◽  
International Agency ◽  
Naphthalene Degradation ◽  
The Us ◽  
Polycyclic Aromatic

Polycyclic aromatic hydrocarbons (PAHs) are a group of aromatic hydrocarbons composed of two or more fused rings and include naphthalene, phenanthrene, pyrene and benzo[a]pyrene amongst others. Exposure to naphthalene has been associated with several toxic manifestations in humans and laboratory animals, with the lens of the eye and the lungs being most sensitive [1]. Additionally, this compound has been reclassified as a possible human carcinogen by the US Environmental Protection Agency and the International Agency for Research on Cancer. It has recently been suggested that naphthalene undergoes metabolic activation to 1,2-naphthoquinone, which reacts with DNA, leading to the formation of apurinic sites on DNA and depurinating DNA adducts [2]. Moreover, a number of studies have attested to the carcinogenic and mutagenic properties of more complex PAHs, suggesting the need for further work on the elimination of these compounds from the environment. The Gram-negative bacterium P. putida G7 is among the best studied naphthalene-degrading species. The genes associated with naphthalene metabolism are localized on NAH7, an 83 kilobase plasmid. In P. putida G7 the naphthalene-oxidation genes are organized into two operons under salicylate control. The first operon (upper naphthalene-degradation pathway) includes the genes nahAaAbAcAdBCDEF, which code for the conversion of naphthalene to salicylate, while the second operon (lower pathway) includes the genes nahGTHINLOMKJ responsible for the oxidation of salicylate via the catechol meta-cleavage pathway [3]. In the last years, our group focused on the structure elucidation and the kinetic characterization of the P. putida G7 enzymes involved in the naphthalene degradation pathway. We intend to present these results which basically describe the 3D structures of NahB, NahF, NahG, NahI, NahK and NahK/NahL complex and some kinetic data of these enzymes and their mutants. This work was supported by FAPEMIG, CNPq and VALE S.A.

scholarly journals Characterization of deltamethrin degradation and metabolic pathway by co-culture of Acinetobacter junii LH-1-1 and Klebsiella pneumoniae BPBA052

2020 ◽  
Author(s):  
Jie Tang ◽  
Qiong Hu ◽  
Dan Lei ◽  
Min Wu ◽  
Chaoyi Zeng ◽  
...  
Keyword(s):  
Klebsiella Pneumoniae ◽  
Contaminated Soils ◽  
Degradation Kinetics ◽  
Degradation Pathway ◽  
Gas Chromatography Mass Spectrometry ◽  
Acinetobacter Junii ◽  
Pyrethroid Pesticides ◽  
First Time ◽  
Kinetics Of

Abstract Deltamethrin and its major metabolite 3-phenoxybenzoic acid (3‐PBA) have caused serious threat to the environment as well as human health, yet little is known about their degradation pathways by bacterial co-cultures. In this study, the growth and degradation kinetics of Acinetobacter junii LH-1-1 and Klebsiella pneumoniae BPBA052 during deltamethrin and 3-PBA degradation were established, respectively. When the inoculum proportion of the strains LH-1-1 and BPBA052 was 7.5:2.5, and LH-1-1 was inoculated 24 h before inoculation of strain BPBA052, 94.25% deltamethrin was degraded and 9.16 mg/L of 3-PBA remained within 72 h, which was 20.36% higher and 10.25 mg/L lesser than that in monoculture of LH-1-1, respectively. And the half-life of deltamethrin was shortened from 38.40 h to 24.58 h. Based on gas chromatography–mass spectrometry, 3-phenoxybenzaldehyde, 1,2-benzenedicarboxylic butyl dacyl ester, and phenol were identified as metabolites during deltamethrin degradation in co-culture. This is the first time that a co-culture degradation pathway of deltamethrin has been proposed based on these identified metabolites. Bioremediation of deltamethrin-contaminated soils with co-culture of strains LH-1-1 and BPBA052 significantly enhanced deltamethrin degradation and 3-PBA removal. This study provides a platform for further studies on deltamethrin and 3-PBA biodegradation mechanism in co-culture, and it also proposes a promising approach for efficient bioremediation of environment contaminated by pyrethroid pesticides and their associated metabolites.

scholarly journals Lignocellulose degradation by Phanerochaete chrysosporium: purification and characterization of the main α-galactosidase

1999 ◽  
Vol 339 (1) ◽  
pp. 43-53 ◽  
Author(s):  
Harry BRUMER ◽  
Paul F. G. SIMS ◽  
Michael L. SINNOTT
Keyword(s):  
Phanerochaete Chrysosporium ◽  
Substrate Inhibition ◽  
Enzyme Reaction ◽  
Lignocellulose Degradation ◽  
K Value ◽  
Softwood Pulp ◽  
Leaving Groups ◽  
Kinetics Of ◽  
Optimal Ph

The main α-galactosidase was purified to homogeneity, in 30% yield, from a solid culture of Phanerochaete chrysosporium on 1 part wheat bran/2 parts thermomechanical softwood pulp. It is a glycosylated tetramer of 50 kDa peptide chains, which gives the N-terminal sequence ADNGLAITPQMG(?W)NT(?W)NHFG(?W)DIS(?W)DTI. It is remarkably stable, with crude extracts losing no activity over 3 h at 80 °C, and the purified enzyme retaining its activity over several months at 4 °C. The kinetics of hydrolysis at 25 °C of various substrates by this retaining enzyme were measured, absolute parameters being obtained by active-site titration with 2´,4´,6´-trinitrophenyl 2-deoxy-2,2-difluoro-α-d-galactopyranoside. The variation of kcat/Km for 1-naphthyl-α-d-galactopyranoside with pH is bell-shaped, with pK1 = 1.91 and pK2 = 5.54. The αD(V/K) value for p-nitrophenyl-α-d-glucopyranoside is 1.031±0.007 at the optimal pH of 3.75 and 1.114±0.006 at pH 7.00, indicating masking of the intrinsic effect at optimal pH. There is no α-2H effect on binding galactose [αD(Ki) = 0.994±0.013]. The enzyme hydrolyses p-nitrophenyl β-l-arabinopyranoside ∼ 510 times slower than the galactoside, but has no detectable activity on the α-d-glucopyranoside or α-d-mannopyranoside. Hydrolysis of α-galactosides with poor leaving groups is Michaelian, but that of substrates with good leaving groups exhibits pronounced apparent substrate inhibition, with Kis values similar to Km values. We attribute this to the binding of the second substrate molecule to a β-galactopyranosyl-enzyme intermediate, forming an E•βGal•αGalX complex which turns over slowly, if at all. 1-Fluoro-α-d-galactopyranosyl fluoride, unlike α-d-galactopyranosyl fluoride, is a Michaelian substrate, indicating that the effect of 1-fluorine substitution is greater on the first than on the second step of the enzyme reaction.

Degradation of Pentachlorophenol by Mycena avenacea TA 8480 - Identification of Initial Dechlorinated Metabolites

1992 ◽  
Vol 47 (7-8) ◽  
pp. 561-566 ◽  
Author(s):  
Stefan Kremer ◽  
Olov Sterner ◽  
Heidrun Anke
Keyword(s):  
Degradation Rate ◽  
Degradation Pathway ◽  
Specific Degradation

Cultures of the basidiomycete Mycena avenacea TA 8480 were shown to metabolize entachlorophenol (PCP), 2,3,5,6-tetrachloro-p-hydroquinone (TeCHQ), and 2,3,5,6-tetrachloro-p- benzoquinone (TeCBQ). The first metabolite of the PCP degradation pathway was identified as TeCBQ which in a second reaction is reduced to the hydroquinone TeCHQ. Subsequently dechlorination of TeCHQ yielded 3,5,6-trichloro-2-hydroxy-p-benzoquinone (TCOHBQ). The specific degradation rate for PCP was 1.4 mg x g dry m ycelia-1 x day-1. The initial dechlorination rate of TeCHQ was 5.9 mg x g dry mycelia-1 x hour-1. None of the compounds supported growth of the fungus.

Irradiation behavior of pyrolytic silicon carbide

1983 ◽  
Vol 41 ◽  
pp. 72-73
Author(s):  
R. J. Lauf
Keyword(s):  
Silicon Carbide ◽  
Fission Products ◽  
Thermodynamics And Kinetics ◽  
Neutron Fluences ◽  
Fuel Particles ◽  
Sic Coatings ◽  
Irradiation Behavior ◽  
Kinetics Of ◽  
Htgr Fuel

Fuel particles for the High-Temperature Gas-Cooled Reactor (HTGR) contain a layer of pyrolytic silicon carbide to act as a miniature pressure vessel and primary fission product barrier. Optimization of the SiC with respect to fuel performance involves four areas of study: (a) characterization of as-deposited SiC coatings; (b) thermodynamics and kinetics of chemical reactions between SiC and fission products; (c) irradiation behavior of SiC in the absence of fission products; and (d) combined effects of irradiation and fission products. This paper reports the behavior of SiC deposited on inert microspheres and irradiated to fast neutron fluences typical of HTGR fuel at end-of-life.

Elaboration and Characterization of the Properties of Refractory Cr Base Alloys

2010 ◽  
Vol 72 ◽  
pp. 46-52 ◽  
Author(s):  
Laurent Royer ◽  
Stéphane Mathieu ◽  
Christophe Liebaut ◽  
Pierre Steinmetz
Keyword(s):  
Mechanical Properties ◽  
Melting Point ◽  
Molten Glass ◽  
Energy Production ◽  
Creep Properties ◽  
Refractory Alloys ◽  
Industrial Use ◽  
Kinetics Of ◽  
Selection Of

For energy production and also for the glass industry, finding new refractory alloys which could permit to increase the process temperatures to 1200°C or more is a permanent challenge. Chromium base alloys can be good candidates, considering the melting point of Cr itself, and also its low corrosion rate in molten glass. Two families of alloys have been studied for this purpose, Cr-Mo-W and Cr-Ta-X alloys (X= Mo, Si..). A finer selection of compositions has been done, to optimize their chemical and mechanical properties. Kinetics of HT oxidation by air, of corrosion by molten glass and also creep properties of several alloys have been measured up to 1250°C. The results obtained with the best alloys (Cr-Ta base) give positive indications as regards the possibility of their industrial use.

scholarly journals New Trimethoprim-Like Molecules: Bacteriological Evaluation and Insights into Their Action

Antibiotics ◽  
2021 ◽  
Vol 10 (6) ◽  
pp. 709
Author(s):  
Marta Jorba ◽  
Marina Pedrola ◽  
Ouldouz Ghashghaei ◽  
Rocío Herráez ◽  
Lluis Campos-Vicens ◽  
...  
Keyword(s):  
Inhibitory Concentration ◽  
Efflux Pump ◽  
Synergistic Effects ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Detailed Characterization ◽  
Low Concentrations ◽  
Pump Activity ◽  
Bacteriological Evaluation ◽  
Kinetics Of

This work reports a detailed characterization of the antimicrobial profile of two trimethoprim-like molecules (compounds 1a and 1b) identified in previous studies. Both molecules displayed remarkable antimicrobial activity, particularly when combined with sulfamethoxazole. In disk diffusion assays on Petri dishes, compounds 1a and 1b showed synergistic effects with colistin. Specifically, in combinations with low concentrations of colistin, very large increases in the activities of compounds 1a and 1b were determined, as demonstrated by alterations in the kinetics of bacterial growth despite only slight changes in the fractional inhibitory concentration index. The effect of colistin may be to increase the rate of antibiotic entry while reducing efflux pump activity. Compounds 1a and 1b were susceptible to extrusion by efflux pumps, whereas the inhibitor phenylalanine arginyl β-naphthylamide (PAβN) exerted effects similar to those of colistin. The interactions between the target enzyme (dihydrofolate reductase), the coenzyme nicotinamide adenine dinucleotide phosphate (NADPH), and the studied molecules were explored using enzymology tools and computational chemistry. A model based on docking results is reported.

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