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Johann Heider - One of the best experts on this subject based on the ideXlab platform.
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asymmetric reduction of ketones and β keto esters by s 1 phenylethanol dehydrogenase from Denitrifying Bacterium aromatoleum aromaticum
Applied Microbiology and Biotechnology, 2015Co-Authors: Agnieszka Dudzik, Wojciech Snoch, Pawel Borowiecki, J Opalinskapiskorz, Malgorzata Witko, Johann Heider, Maciej SzaleniecAbstract:Enzyme-catalyzed enantioselective reductions of ketones and keto esters have become popular for the production of homochiral building blocks which are valuable synthons for the preparation of biologically active compounds at industrial scale. Among many kinds of biocatalysts, dehydrogenases/reductases from various microorganisms have been used to prepare optically pure enantiomers from carbonyl compounds. (S)-1-phenylethanol dehydrogenase (PEDH) was found in the Denitrifying Bacterium Aromatoleum aromaticum (strain EbN1) and belongs to the short-chain dehydrogenase/reductase family. It catalyzes the stereospecific oxidation of (S)-1-phenylethanol to acetophenone during anaerobic ethylbenzene mineralization, but also the reverse reaction, i.e., NADH-dependent enantioselective reduction of acetophenone to (S)-1-phenylethanol. In this work, we present the application of PEDH for asymmetric reduction of 42 prochiral ketones and 11 β-keto esters to enantiopure secondary alcohols. The high enantioselectivity of the reaction is explained by docking experiments and analysis of the interaction and binding energies of the theoretical enzyme-substrate complexes leading to the respective (S)- or (R)-alcohols. The conversions were carried out in a batch reactor using Escherichia coli cells with heterologously produced PEDH as whole-cell catalysts and isopropanol as reaction solvent and cosubstrate for NADH recovery. Ketones were converted to the respective secondary alcohols with excellent enantiomeric excesses and high productivities. Moreover, the progress of product formation was studied for nine para-substituted acetophenone derivatives and described by neural network models, which allow to predict reactor behavior and provides insight on enzyme reactivity. Finally, equilibrium constants for conversion of these substrates were derived from the progress curves of the reactions. The obtained values matched very well with theoretical predictions.
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Crystal Structure and Enzyme Kinetics of the (S)-Specific 1-Phenylethanol Dehydrogenase of the Denitrifying Bacterium Strain EbN1†,‡
Biochemistry, 2006Co-Authors: H. Wolfgang Höffken, Minh Duong, Michael Breuer, Bernhard Hauer, Richard Reinhardt, Ralf Rabus, Thomas Friedrich, Johann HeiderAbstract:(S)-1-Phenylethanol dehydrogenase (PED) from the Denitrifying Bacterium strain EbN1 catalyzes the NAD+-dependent, stereospecific oxidation of (S)-1-phenylethanol to acetophenone and the biotechnologically interesting reverse reaction. This novel enzyme belongs to the short-chain alcohol dehydrogenase/aldehyde reductase family. The coding gene (ped) was heterologously expressed in Escherichia coli and the purified protein was crystallized. The X-ray structures of the apo-form and the NAD+-bound form were solved at a resolution of 2.1 and 2.4 A, respectively, revealing that the enzyme is a tetramer with two types of hydrophobic dimerization interfaces, similar to β-oxoacyl-[acyl carrier protein] reductase (FabG) from E. coli. NAD+-binding is associated with a conformational shift of the substrate binding loop of PED from a crystallographically unordered “open” to a more ordered “closed” form. Modeling the substrate acetophenone into the active site revealed the structural prerequisites for the strong enanti...
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crystal structure and enzyme kinetics of the s specific 1 phenylethanol dehydrogenase of the Denitrifying Bacterium strain ebn1
Biochemistry, 2006Co-Authors: Wolfgang H Hoffken, Minh Duong, Michael Breuer, Bernhard Hauer, Richard Reinhardt, Ralf Rabus, Thomas Friedrich, Johann HeiderAbstract:(S)-1-Phenylethanol dehydrogenase (PED) from the Denitrifying Bacterium strain EbN1 catalyzes the NAD+-dependent, stereospecific oxidation of (S)-1-phenylethanol to acetophenone and the biotechnologically interesting reverse reaction. This novel enzyme belongs to the short-chain alcohol dehydrogenase/aldehyde reductase family. The coding gene (ped) was heterologously expressed in Escherichia coli and the purified protein was crystallized. The X-ray structures of the apo-form and the NAD+-bound form were solved at a resolution of 2.1 and 2.4 A, respectively, revealing that the enzyme is a tetramer with two types of hydrophobic dimerization interfaces, similar to β-oxoacyl-[acyl carrier protein] reductase (FabG) from E. coli. NAD+-binding is associated with a conformational shift of the substrate binding loop of PED from a crystallographically unordered “open” to a more ordered “closed” form. Modeling the substrate acetophenone into the active site revealed the structural prerequisites for the strong enanti...
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Differential induction of enzymes involved in anaerobic metabolism of aromatic compounds in the Denitrifying Bacterium Thauera aromatica.
Archives of Microbiology, 1998Co-Authors: Johann Heider, Diana Laempe, Klaus Breese, Matthias Boll, Ulrich Feil, Sabine Breinig, Christa Ebenau-jehle, Nasser Gad'on, Birgitta Leuthner, M. El-said MohamedAbstract:Differential induction of enzymes involved in anaerobic metabolism of aromatic substrates was studied in the Denitrifying Bacterium Thauera aromatica. This metabolism is divided into (1) peripheral reactions transforming the aromatic growth substrates to the common intermediate benzoyl-CoA, (2) the central benzoyl-CoA pathway comprising ring-reduction of benzoyl-CoA and subsequent β-oxidation to 3-hydroxypimelyl-CoA, and (3) the pathway of β-oxidation of 3-hydroxypimelyl-CoA to three acetyl-CoA and CO2. Regulation was studied by three methods. 1. Determination of protein patterns of cells grown on different substrates. This revealed several strongly substrate-induced polypeptides that were missing in cells grown on benzoate or other intermediates of the respective metabolic pathways. 2. Measurement of activities of known enzymes involved in this metabolism in cells grown on different substrates. The enzyme pattern found is consistent with the regulatory pattern deduced from simultaneous adaptation of cells to utilisation of other aromatic substrates. 3. Immunological detection of catabolic enzymes in cells grown on different substrates. Benzoate-CoA ligase and 4-hydroxybenzoate-CoA ligase were detected only in cells yielding the respective enzyme activity. However, presence of the subunits of benzoyl-CoA reductase and 4-hydroxybenzoyl-CoA reductase was also recorded in some cell batches lacking enzyme activity. This possibly indicates an additional level of regulation on protein level for these two reductases.
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Evidence that anaerobic oxidation of toluene in the Denitrifying Bacterium Thauera aromatica is initiated by formation of benzylsuccinate from toluene and fumarate.
FEBS Journal, 1996Co-Authors: Thomas Biegert, Georg Fuchs, Johann HeiderAbstract:Toluene is degraded anoxically to CO2 by the Denitrifying Bacterium Thauera aromatica. Toluene first becomes oxidized to benzoyl-CoA by O2-independent reactions. Benzoyl-CoA is then reduced to non-aromatic products by benzoyl-CoA reductase. We set out to study the reactions employed for the initial activation of toluene and its oxidation to the level of benzoate. Evidence is provided for a novel way of toluene degradation based on experiments with cell-free extracts and with whole toluene-grown cells: Cell-free extracts oxidized [14C]toluene to [14C]benzoyl-CoA via several radioactive intermediates. This reaction was strictly dependent on the presence of fumarate, coenzyme A and nitrate as electron acceptor; acetyl-CoA and ATP were not necessary for the reaction. The first product formed in vitro was benzylsuccinate; (2H8)toluene was converted to (2H7)benzylsuccinate. Formation of benzylsuccinate from toluene was independent of coenzyme A and nitrate, but it required the presence of fumarate. Other tricarboxylic acid cycle intermediates were converted to fumarate in cell extracts and therefore could partially substitute for fumarate. [14C]Benzylsuccinate was oxidized further to [14C]benzoyl-CoA and [14C]benzoate in cell extracts if coenzyme A and nitrate were present. No benzyl alcohol and benzaldehyde and no phenylpropionate could be detected as intermediates. In isotope trapping experiments with cell suspensions, two intermediates from [14C]toluene were detected, benzoate and benzylsuccinate. This corroborates the sequence of reactions deduced from in vitro experiments. A hypothetical degradation pathway for the anaerobic oxidation of toluene to benzoyl-CoA via an initial addition of fumarate to the methyl group of toluene and following β-oxidation of the benzylsuccinate formed is suggested.
Georg Fuchs - One of the best experts on this subject based on the ideXlab platform.
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Anaerobic metabolism of 3-hydroxybenzoate by the Denitrifying Bacterium Thauera aromatica.
Journal of Bacteriology, 2001Co-Authors: Diana Laempe, Klaus Breese, Martina Jahn, Hermann Schägger, Georg FuchsAbstract:The anaerobic metabolism of 3-hydroxybenzoate was studied in the Denitrifying Bacterium Thauera aromatica. Cells grown with this substrate were adapted to grow with benzoate but not with 4-hydroxybenzoate. Vice versa, 4-hydroxybenzoate-grown cells did not utilize 3-hydroxybenzoate. The first step in 3-hydroxybenzoate metabolism is a coenzyme A (CoA) thioester formation, which is catalyzed by an inducible 3-hydroxybenzoate–CoA ligase. The enzyme was purified and characterized. Further metabolism of 3-hydroxybenzoyl-CoA by cell extract required MgATP and was coupled to the oxidation of 2 mol of reduced viologen dyes per mol of substrate added. Purification of the 3-hydroxybenzoyl-CoA reducing enzyme revealed that this activity was due to benzoyl-CoA reductase, which reduced the 3-hydroxy analogue almost as efficiently as benzoyl-CoA. The further metabolism of the alicyclic dienoyl-CoA product containing the hydroxyl substitution obviously required additional specific enzymes. Comparison of the protein pattern of 3-hydroxybenzoate-grown cells with benzoate-grown cells revealed several 3-hydroxybenzoate-induced proteins; the N-terminal amino acid sequences of four induced proteins were determined and the corresponding genes were identified and sequenced. A cluster of six adjacent genes contained the genes for substrate-induced proteins 1 to 3; this cluster may not yet be complete. Protein 1 is a short-chain alcohol dehydrogenase. Protein 2 is a member of enoyl-CoA hydratase enzymes. Protein 3 was identified as 3-hydroxybenzoate–CoA ligase. Protein 4 is another member of the enoyl-CoA hydratases. In addition, three genes coding for enzymes of β-oxidation were present. The anaerobic 3-hydroxybenzoate metabolism here obviously combines an enzyme (benzoyl-CoA reductase) and electron carrier (ferredoxin) of the general benzoyl-CoA pathway with enzymes specific for the 3-hydroxybenzoate pathway. This raises some questions concerning the regulation of both pathways.
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Anaerobic Metabolism of 3-Hydroxybenzoate by the Denitrifying Bacterium Thauera aromatica
Journal of bacteriology, 2001Co-Authors: Diana Laempe, Klaus Breese, Martina Jahn, Hermann Schägger, Georg FuchsAbstract:The anaerobic metabolism of 3-hydroxybenzoate was studied in the Denitrifying Bacterium Thauera aromatica. Cells grown with this substrate were adapted to grow with benzoate but not with 4-hydroxybenzoate. Vice versa, 4-hydroxybenzoate-grown cells did not utilize 3-hydroxybenzoate. The first step in 3-hydroxybenzoate metabolism is a coenzyme A (CoA) thioester formation, which is catalyzed by an inducible 3-hydroxybenzoate-CoA ligase. The enzyme was purified and characterized. Further metabolism of 3-hydroxybenzoyl-CoA by cell extract required MgATP and was coupled to the oxidation of 2 mol of reduced viologen dyes per mol of substrate added. Purification of the 3-hydroxybenzoyl-CoA reducing enzyme revealed that this activity was due to benzoyl-CoA reductase, which reduced the 3-hydroxy analogue almost as efficiently as benzoyl-CoA. The further metabolism of the alicyclic dienoyl-CoA product containing the hydroxyl substitution obviously required additional specific enzymes. Comparison of the protein pattern of 3-hydroxybenzoate-grown cells with benzoate-grown cells revealed several 3-hydroxybenzoate-induced proteins; the N-terminal amino acid sequences of four induced proteins were determined and the corresponding genes were identified and sequenced. A cluster of six adjacent genes contained the genes for substrate-induced proteins 1 to 3; this cluster may not yet be complete. Protein 1 is a short-chain alcohol dehydrogenase. Protein 2 is a member of enoyl-CoA hydratase enzymes. Protein 3 was identified as 3-hydroxybenzoate-CoA ligase. Protein 4 is another member of the enoyl-CoA hydratases. In addition, three genes coding for enzymes of beta-oxidation were present. The anaerobic 3-hydroxybenzoate metabolism here obviously combines an enzyme (benzoyl-CoA reductase) and electron carrier (ferredoxin) of the general benzoyl-CoA pathway with enzymes specific for the 3-hydroxybenzoate pathway. This raises some questions concerning the regulation of both pathways.
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Phenylacetyl-CoA:acceptor oxidoreductase, a membrane-bound molybdenum-iron-sulfur enzyme involved in anaerobic metabolism of phenylalanine in the Denitrifying Bacterium Thauera aromatica.
European Journal of Biochemistry, 1999Co-Authors: Sung-keun Rhee, Georg FuchsAbstract:Phenylacetic acids are common intermediates in the microbial metabolism of various aromatic substrates including phenylalanine. In the Denitrifying Bacterium Thauera aromatica phenylacetate is oxidized, under anoxic conditions, to the common intermediate benzoyl-CoA via the intermediates phenylacetyl-CoA and phenylglyoxylate (benzoylformate). The enzyme that catalyzes the four-electron oxidation of phenylacetyl-CoA has been purified from this Bacterium and studied. The enzyme preparation catalyzes the reaction phenylacetyl-CoA + 2 quinone + 2 H2O --> phenylglyoxylate + 2 quinone H2 + CoASH. Phenylacetyl-CoA:acceptor oxidoreductase is a membrane-bound molybdenum-iron-sulfur protein. The purest preparations contained three subunits of 93, 27, and 26 kDa. Ubiquinone is most likely to act as the electron acceptor, and the oxygen atom introduced into the product is derived from water. The protein preparations contained 0.66 mol Mo, 30 mol Fe, and 25 mol acid-labile sulfur per mol of native enzyme, assuming a native molecular mass of 280 kDa. Phenylglyoxylyl-CoA, but not mandelyl-CoA, was observed as a free intermediate. All enzyme preparations also catalyzed the subsequent hydrolytic release of coenzyme A from phenylglyoxylyl-CoA but not from phenylacetyl-CoA. The enzyme is reversibly inactivated by a low concentration of cyanide, but is remarkably stable with respect to oxygen. This new member of the molybdoproteins represents the first example of an enzyme which catalyzes the alpha-oxidation of a CoA-activated carboxylic acid without utilizing molecular oxygen.
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Cyclohexa‐1,5‐diene‐1‐carboxyl‐CoA hydratase, an enzyme involved in anaerobic metabolism of benzoyl‐CoA in the Denitrifying Bacterium Thauera aromatica
FEBS Journal, 1998Co-Authors: Diana Laempe, Wolfgang Eisenreich, Adelbert Bacher, Georg FuchsAbstract:Many aromatic compounds can be metabolized by bacteria under anoxic conditions via benzoyl-CoA as the common intermediate. The central pathway of benzoyl-CoA metabolism is initiated by an ATP-driven reduction of the aromatic ring producing cyclohexa-1,5-diene-1-carboxyl-CoA. The 1,5-dienoyl-CoA intermediate is thought to be transformed to 6-hydroxycyclohex-1-ene-1-carboxyl-CoA by a specific dienoyl-CoA hydratase catalyzing the formal addition of water to one of the double bonds. This dienoyl-CoA hydratase was detected in the Denitrifying Bacterium Thauera aromatica after anaerobic growth with benzoate. Substrate and product were confirmed and a convenient spectrophotometric assay was developed. The equilibrium concentrations of substrate and product were almost equal. Enzyme activity was induced after anoxic growth with benzoate, in contrast to acetate. The enzyme of 28 kDa was purified from T. aromatica and was found to be highly specific for the cyclic 1,5-dienoyl-CoA. A second 29-kDa enoyl-CoA hydratase acted on crotonyl-CoA; this highly active enoyl-CoA hydratase also acted slowly on cyclohex-1-ene-1-carboxyl-CoA. The regulation of expression of dienoyl-CoA hydratase activity, the kinetic constants, the substrate specificity, and the specific activity of the enzyme in cell extract provide evidence that dienoyl-CoA hydratase is the second enzyme of the central benzoyl-CoA pathway of anaerobic aromatic metabolism in T. aromatica. Extracts of Rhodopseudomonas palustris contained high activity of cyclohex-1-ene-1-carboxyl-CoA hydratase, but no 1,5-dienoyl-CoA hydratase activity. It appears that a variant of the benzoyl-CoA pathway is operating in R. palustris in which hydration of the 1,5-dienoyl-CoA does not take place. Rather, cyclohex-1-ene-1-carboxyl-CoA is hydrated to 2-hydroxycyclohexane-1-carboxyl-CoA.
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cyclohexa 1 5 diene 1 carboxyl coa hydratase an enzyme involved in anaerobic metabolism of benzoyl coa in the Denitrifying Bacterium thauera aromatica
FEBS Journal, 1998Co-Authors: Diana Laempe, Wolfgang Eisenreich, Adelbert Bacher, Georg FuchsAbstract:Many aromatic compounds can be metabolized by bacteria under anoxic conditions via benzoyl-CoA as the common intermediate. The central pathway of benzoyl-CoA metabolism is initiated by an ATP-driven reduction of the aromatic ring producing cyclohexa-1,5-diene-1-carboxyl-CoA. The 1,5-dienoyl-CoA intermediate is thought to be transformed to 6-hydroxycyclohex-1-ene-1-carboxyl-CoA by a specific dienoyl-CoA hydratase catalyzing the formal addition of water to one of the double bonds. This dienoyl-CoA hydratase was detected in the Denitrifying Bacterium Thauera aromatica after anaerobic growth with benzoate. Substrate and product were confirmed and a convenient spectrophotometric assay was developed. The equilibrium concentrations of substrate and product were almost equal. Enzyme activity was induced after anoxic growth with benzoate, in contrast to acetate. The enzyme of 28 kDa was purified from T. aromatica and was found to be highly specific for the cyclic 1,5-dienoyl-CoA. A second 29-kDa enoyl-CoA hydratase acted on crotonyl-CoA; this highly active enoyl-CoA hydratase also acted slowly on cyclohex-1-ene-1-carboxyl-CoA. The regulation of expression of dienoyl-CoA hydratase activity, the kinetic constants, the substrate specificity, and the specific activity of the enzyme in cell extract provide evidence that dienoyl-CoA hydratase is the second enzyme of the central benzoyl-CoA pathway of anaerobic aromatic metabolism in T. aromatica. Extracts of Rhodopseudomonas palustris contained high activity of cyclohex-1-ene-1-carboxyl-CoA hydratase, but no 1,5-dienoyl-CoA hydratase activity. It appears that a variant of the benzoyl-CoA pathway is operating in R. palustris in which hydration of the 1,5-dienoyl-CoA does not take place. Rather, cyclohex-1-ene-1-carboxyl-CoA is hydrated to 2-hydroxycyclohexane-1-carboxyl-CoA.
Ralf Rabus - One of the best experts on this subject based on the ideXlab platform.
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Crystal Structure and Enzyme Kinetics of the (S)-Specific 1-Phenylethanol Dehydrogenase of the Denitrifying Bacterium Strain EbN1†,‡
Biochemistry, 2006Co-Authors: H. Wolfgang Höffken, Minh Duong, Michael Breuer, Bernhard Hauer, Richard Reinhardt, Ralf Rabus, Thomas Friedrich, Johann HeiderAbstract:(S)-1-Phenylethanol dehydrogenase (PED) from the Denitrifying Bacterium strain EbN1 catalyzes the NAD+-dependent, stereospecific oxidation of (S)-1-phenylethanol to acetophenone and the biotechnologically interesting reverse reaction. This novel enzyme belongs to the short-chain alcohol dehydrogenase/aldehyde reductase family. The coding gene (ped) was heterologously expressed in Escherichia coli and the purified protein was crystallized. The X-ray structures of the apo-form and the NAD+-bound form were solved at a resolution of 2.1 and 2.4 A, respectively, revealing that the enzyme is a tetramer with two types of hydrophobic dimerization interfaces, similar to β-oxoacyl-[acyl carrier protein] reductase (FabG) from E. coli. NAD+-binding is associated with a conformational shift of the substrate binding loop of PED from a crystallographically unordered “open” to a more ordered “closed” form. Modeling the substrate acetophenone into the active site revealed the structural prerequisites for the strong enanti...
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crystal structure and enzyme kinetics of the s specific 1 phenylethanol dehydrogenase of the Denitrifying Bacterium strain ebn1
Biochemistry, 2006Co-Authors: Wolfgang H Hoffken, Minh Duong, Michael Breuer, Bernhard Hauer, Richard Reinhardt, Ralf Rabus, Thomas Friedrich, Johann HeiderAbstract:(S)-1-Phenylethanol dehydrogenase (PED) from the Denitrifying Bacterium strain EbN1 catalyzes the NAD+-dependent, stereospecific oxidation of (S)-1-phenylethanol to acetophenone and the biotechnologically interesting reverse reaction. This novel enzyme belongs to the short-chain alcohol dehydrogenase/aldehyde reductase family. The coding gene (ped) was heterologously expressed in Escherichia coli and the purified protein was crystallized. The X-ray structures of the apo-form and the NAD+-bound form were solved at a resolution of 2.1 and 2.4 A, respectively, revealing that the enzyme is a tetramer with two types of hydrophobic dimerization interfaces, similar to β-oxoacyl-[acyl carrier protein] reductase (FabG) from E. coli. NAD+-binding is associated with a conformational shift of the substrate binding loop of PED from a crystallographically unordered “open” to a more ordered “closed” form. Modeling the substrate acetophenone into the active site revealed the structural prerequisites for the strong enanti...
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Functional genomics of an anaerobic aromatic-degrading Denitrifying Bacterium, strain EbN1
Applied Microbiology and Biotechnology, 2005Co-Authors: Ralf RabusAbstract:Nitrate-reducing bacteria of the recently recognized Azoarcus / Thauera group within the Betaproteobacteria contribute significantly to the biodegradation of aromatic and other refractory compounds in anoxic waters and soils. Strain EbN1 belongs to a distinct cluster (new genus) and is the first member of this phylogenetic group, the genome of which has been determined (4.7 Mb; one chromosome, two plasmids) by [Rabus R, Kube M, Heider J, Beck A, Heitmann K, Widdel F, Reinhardt R (2005) The genome sequence of an anaerobic aromatic-degrading Denitrifying Bacterium, strain EbN1. Arch Microbiol 183:27–36]. Ten anaerobic and four aerobic aromatic-degradation pathways were recognized on the chromosome, with the coding genes mostly forming clusters. Presence of paralogous gene clusters (e.g. for anaerobic ethylbenzene degradation) suggests an even broader degradation spectrum than previously known. Metabolic versatility is also reflected by the presence of multiple respiratory complexes and is apparently controlled by an extensive regulatory network. Strain EbN1 is unique for its capacity to degrade toluene and ethylbenzene anaerobically via completely different pathways. Bioinformatical analysis of their genetic blueprints and global expression analysis (DNA-microarray and proteomics) of substrate-adapted cells [Kühner S, Wöhlbrand L, Fritz I, Wruck W, Hultschig C, Hufnagel P, Kube M, Reinhardt R, Rabus R (2005) Substrate-dependent regulation of anaerobic degradation pathways for toluene and ethylbenzene in a Denitrifying Bacterium, strain EbN1. J Bacteriol 187:1493–1503] indicated coordinated vs sequential modes of regulation for the toluene and ethylbenzene pathways, respectively.
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Formation of n-alkane- and cycloalkane-derived organic acids during anaerobic growth of a Denitrifying Bacterium with crude oil
Organic Geochemistry, 2003Co-Authors: Heinz Wilkes, Simon Kühner, Carsten Bolm, Thomas Fischer, Arno Classen, Friedrich Widdel, Ralf RabusAbstract:Abstract The formation of metabolites during anaerobic biodegradation of saturated hydrocarbons directly from crude oil in the absence of oxygen was investigated using a Denitrifying Bacterium, the Azoarcus -like strain HxN1, which can utilise C 6 –C 8 n -alkanes anaerobically as growth substrates. Various alkylsuccinates (apparently diastereomers) with alkyl chains (probably linked at C-2) ranging from C 4 to C 8 were detected by gas chromatography–mass spectrometry. These metabolites apparently result from the activation reaction of C 4 –C 8 alkanes with cellular fumarate, analogous to the recently established reaction of pure n -hexane with fumarate in strain HxN1 to yield (1-methylpentyl)succinate. Other succinates carried substituents derived from cyclopentane and methylcyclopentane and hence indicated an activation of such cycloalkanes. Since n -butane, n -pentane or cycloalkanes as single compounds did not support growth of strain HxN1, their apparent products point to co-metabolic reactions during utilisation of the C 6 –C 8 n -alkanes. Furthermore, methyl-branched and cyclopentyl-substituted fatty acids were detected. This finding is explained by a further metabolism of the substituted succinates via carbon skeleton rearrangement and decarboxylation. All metabolites detected in the oil-grown cultures were also identified in cultures grown with defined mixtures of saturated hydrocarbons. Results are of potential value for an understanding of metabolite formation in hydrocarbon-rich anoxic environments from the viewpoint of bacterial physiology.
Yongqing Zhang - One of the best experts on this subject based on the ideXlab platform.
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Cr(VI) removal from aqueous solution by thermophilic Denitrifying Bacterium Chelatococcus daeguensis TAD1 in the presence of single and multiple heavy metals
Journal of Microbiology, 2016Co-Authors: Shaobin Huang, Yongqing ZhangAbstract:Cr(VI) pollution is increasing continuously as a result of ongoing industrialization. In this study, we investigated the thermophilic Denitrifying Bacterium Chelatococcus daeguensis TAD1, isolated from the biofilm of a biotrickling filter used in nitrogen oxides (NOX) removal, with respect to its ability to remove Cr(VI) from an aqueous solution. TAD1 was capable of reducing Cr(VI) from an initial concentration of 10 mg/L to non-detectable levels over a pH range of 7-9 and at a temperature range of 30-50°C. TAD1 simultaneously removed both Cr(VI) and NO3 (-)-N at 50°C, when the pH was 7 and the initial Cr(VI) concentration was 15 mg/L. The reduction of Cr(VI) to Cr(III) correlated with the growth metabolic activity of TAD1. The presence of other heavy metals (Cu, Zn, and Ni) inhibited the ability of TAD1 to remove Cr(VI). The metals each individually inhibited Cr(VI) removal, and the extent of inhibition increased in a cooperative manner in the presence of a combination of the metals. The addition of biodegradable cellulose acetate microspheres (an adsorption material) weakened the toxicity of the heavy metals; in their presence, the Cr(VI) removal efficiency returned to a high level. The feasibility and applicability of simultaneous nitrate removal and Cr(VI) reduction by strain TAD1 is promising, and may be an effective biological method for the clean-up of wastewater.
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Characterization of nitrous oxide emissions from a thermophilic Denitrifying Bacterium Chelatococcus daeguensis TAD1 in an aerated sequencing batch reactor
Biochemical Engineering Journal, 2016Co-Authors: Menglan Pan, Shaofeng Zhou, Shaobin Huang, Yongqing ZhangAbstract:Abstract This study was conducted to investigate the nitrogen removal efficiency and N2O emission characteristics of a novel thermophilic aerobic Denitrifying Bacterium, Chelatococcus daeguensis TAD1, under different C/N ratios and pH values in a batch reactor. Nitrogen removal efficiency and N2O emissions were dramatically influenced by C/N ratio and pH. Moreover, multifactor analysis of variance suggested that these two factors also had significant interaction effects on N2O emissions. The optimum C/N ratio was determined to be 8 (where pH was set to 7), at which a very high nitrogen removal efficiency (>99%) was achieved. Under these conditions, N2O emissions were only 34.43 μg/L and the N2O emission factor was 0.046%, which could offer a promising new microbial resource for N removal and reduction of greenhouse gas emissions during wastewater treatment.
Sung Taik Lee - One of the best experts on this subject based on the ideXlab platform.
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Azonexus caeni sp. nov., a Denitrifying Bacterium isolated from sludge of a wastewater treatment plant.
International Journal of Systematic and Evolutionary Microbiology, 2006Co-Authors: Zhe-xue Quan, Sung Taik LeeAbstract:A polyphasic taxonomic study was carried out to determine the taxonomic position of a newly isolated Denitrifying Bacterium, designated Slu-05T, which had been isolated from sludge from the main aerobic treatment tanks of a municipal sewage treatment plant. Phylogenetic analysis based on comparative 16S rRNA gene sequencing indicated that strain Slu-05T was closely related to Azonexus fungiphilus LMG 19178T (96.4 % sequence similarity), the sole species in the genus Azonexus. Strain Slu-05T comprised Gram-negative, motile, non-spore-forming and slightly curved rods. The predominant respiratory lipoquinone was Q-8. The major fatty acids were C16 : 1 ω7c, C16 : 0, C18 : 1 isomers and C10 : 0 3-OH. The G+C content of the genomic DNA was 65.6 mol%. The results of DNA–DNA hybridization (15.6 %) together with phenotypic determination showed that strain Slu-5T could be distinguished from A. fungiphilus. Moreover, some phenotypic properties concerning enzyme activity, the substrates utilized as carbon sources and growth conditions distinguish strain Slu-5T from A. fungiphilus. On the basis of the results obtained in this study, Slu-05T (=DSM 17719T=KCTC 12530T=CCBAU 10199T) is the type strain of a novel species of Azonexus, for which the name Azonexus caeni sp. nov. is proposed.
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Azonexus caeni sp. nov., a Denitrifying Bacterium isolated from sludge of a wastewater treatment plant.
International journal of systematic and evolutionary microbiology, 2006Co-Authors: Zhe-xue Quan, Sung Taik LeeAbstract:A polyphasic taxonomic study was carried out to determine the taxonomic position of a newly isolated Denitrifying Bacterium, designated Slu-05T, which had been isolated from sludge from the main aerobic treatment tanks of a municipal sewage treatment plant. Phylogenetic analysis based on comparative 16S rRNA gene sequencing indicated that strain Slu-05T was closely related to Azonexus fungiphilus LMG 19178T (96.4 % sequence similarity), the sole species in the genus Azonexus. Strain Slu-05T comprised Gram-negative, motile, non-spore-forming and slightly curved rods. The predominant respiratory lipoquinone was Q-8. The major fatty acids were C16:1omega7c, C16:0, C18:1 isomers and C10:0 3-OH. The G+C content of the genomic DNA was 65.6 mol%. The results of DNA-DNA hybridization (15.6 %) together with phenotypic determination showed that strain Slu-5T could be distinguished from A. fungiphilus. Moreover, some phenotypic properties concerning enzyme activity, the substrates utilized as carbon sources and growth conditions distinguish strain Slu-5T from A. fungiphilus. On the basis of the results obtained in this study, Slu-05T (=DSM 17719T=KCTC 12530T=CCBAU 10199T) is the type strain of a novel species of Azonexus, for which the name Azonexus caeni sp. nov. is proposed.
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Anaerobic and aerobic degradation of pyridine by a newly isolated Denitrifying Bacterium.
Applied and environmental microbiology, 1997Co-Authors: Sung-keun Rhee, Gyun Min Lee, Jung Hoon Yoon, Yong Ha Park, Hee Sung Bae, Sung Taik LeeAbstract:New Denitrifying bacteria that could degrade pyridine under both aerobic and anaerobic conditions were isolated from industrial wastewater. The successful enrichment and isolation of these strains required selenite as a trace element. These isolates appeared to be closely related to Azoarcus species according to the results of 16S rRNA sequence analysis. An isolated strain, pF6, metabolized pyridine through the same pathway under both aerobic and anaerobic conditions. Since pyridine induced NAD-linked glutarate-dialdehyde dehydrogenase and isocitratase activities, it is likely that the mechanism of pyridine degradation in strain pF6 involves N-C-2 ring cleavage. Strain pF6 could degrade pyridine in the presence of nitrate, nitrite, and nitrous oxide as electron acceptors. In a batch culture with 6 mM nitrate, degradation of pyridine and denitrification were not sensitively affected by the redox potential, which gradually decreased from 150 to -200 mV. In a batch culture with the nitrate concentration higher than 6 mM, nitrite transiently accumulated during denitrification significantly inhibited cell growth and pyridine degradation. Growth yield on pyridine decreased slightly under Denitrifying conditions from that under aerobic conditions. Furthermore, when the pyridine concentration used was above 12 mM, the specific growth rate under Denitrifying conditions was higher than that under aerobic conditions. Considering these characteristics, a newly isolated Denitrifying Bacterium, strain pF6, has advantages over strictly aerobic bacteria in field applications.