The Experts below are selected from a list of 7641 Experts worldwide ranked by ideXlab platform
Andreas Heumann - One of the best experts on this subject based on the ideXlab platform.
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an efficient synthesis of β hydroxyethylpyrazoles from propylene and Styrene Oxide using cs2co3
Tetrahedron Letters, 2004Co-Authors: Virginie Duprez, Andreas HeumannAbstract:Bases such as caesium carbonate efficiently catalyze the regioselective ring opening of propylene and Styrene Oxide with various substituted pyrazoles.
Marcel Wubbolts - One of the best experts on this subject based on the ideXlab platform.
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production of enantiopure Styrene Oxide by recombinant escherichia coli synthesizing a two component Styrene monooxygenase
Biotechnology and Bioengineering, 2000Co-Authors: Sven Panke, Marcel Wubbolts, Andreas Schmid, Bernard WitholtAbstract:A whole cell biocatalytic process was developed to enable the efficient oxidation of Styrene to chiral (S)-Styrene Oxide with an enantiomeric excess better than 99%. Recombinant Escherichia coli cells were employed to express the genes styAB encoding the Styrene monooxygenase of Pseudomonas sp. strain VLB120 from an expression plasmid utilizing the alk regulatory system of P. oleovorans GPo1. The strains reached specific activities of up to 70 U* (g cell dry weight)(-1) in shake-flask experiments with glucose as the carbon source. An efficient two-liquid phase fed-batch process was established for the production of (S)-Styrene Oxide with hexadecane as an apolar carrier solvent and a nutrient feed consisting of glucose, magnesium sulfate, and yeast extract. Engineering of the phase fraction and the composition of organic phase and feed led to a 2-L scale process with maximal volumetric productivities of 2.2 g (S)-Styrene Oxide per liter liquid volume per hour. This optimized process was based completely on defined medium and used bis(2-ethylhexyl)phthalate as the apolar carrier solvent, which together with substrate and inducer consisted of 50% of the total liquid volume. Using this system, we were able to produce per liter liquid volume 11 g of enantiopure (S)-Styrene Oxide in 10 h.
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towards a biocatalyst for s Styrene Oxide production characterization of the Styrene degradation pathway of pseudomonas sp strain vlb120
Applied and Environmental Microbiology, 1998Co-Authors: Sven Panke, Bernard Witholt, Andreas Schmid, Marcel WubboltsAbstract:In order to design a biocatalyst for the production of optically pure Styrene Oxide, an important building block in organic synthesis, the metabolic pathway and molecular biology of Styrene degradation in Pseudomonas sp. strain VLB120 was investigated. A 5.7-kb XhoI fragment, which contained on the same strand of DNA six genes involved in Styrene degradation, was isolated from a gene library of this organism in Escherichia coli by screening for indigo formation. T7 RNA polymerase expression experiments indicated that this fragment coded for at least five complete polypeptides, StyRABCD, corresponding to five of the six genes. The first two genes encoded the potential carboxy-terminal part of a sensor, named StySc, and the complete response regulator StyR. Fusion of the putative styAp promoter to a lacZ reporter indicated that StySc and StyR together regulate expression of the structural genes at the transcriptional level. Expression of styScR also alleviated a block that prevented translation of styA mRNA when a heterologous promoter was used. The structural genes styA and styB produced a Styrene monooxygenase that converted Styrene to Styrene Oxide, which was then converted to phenylacetaldehyde by StyC. Sequence homology analysis of StyD indicated a probable function as a phenylacetaldehyde dehydrogenase. To assess the usefulness of the enzymes for the production of enantiomerically pure Styrene Oxide, we investigated the enantiospecificities of the reactions involved. Kinetic resolution of racemic Styrene Oxide by Styrene Oxide isomerase was studied with E. coli recombinants carrying styC, which converted Styrene Oxide at a very high rate but with only a slight preference for the S enantiomer. However, recombinants producing Styrene monooxygenase catalyzed the formation of (S)-Styrene Oxide from inexpensive Styrene with an excellent enantiomeric excess of more than 99% at rates up to 180 U g (dry weight) of cells-1.
Virginie Duprez - One of the best experts on this subject based on the ideXlab platform.
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an efficient synthesis of β hydroxyethylpyrazoles from propylene and Styrene Oxide using cs2co3
Tetrahedron Letters, 2004Co-Authors: Virginie Duprez, Andreas HeumannAbstract:Bases such as caesium carbonate efficiently catalyze the regioselective ring opening of propylene and Styrene Oxide with various substituted pyrazoles.
Sven Panke - One of the best experts on this subject based on the ideXlab platform.
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production of enantiopure Styrene Oxide by recombinant escherichia coli synthesizing a two component Styrene monooxygenase
Biotechnology and Bioengineering, 2000Co-Authors: Sven Panke, Marcel Wubbolts, Andreas Schmid, Bernard WitholtAbstract:A whole cell biocatalytic process was developed to enable the efficient oxidation of Styrene to chiral (S)-Styrene Oxide with an enantiomeric excess better than 99%. Recombinant Escherichia coli cells were employed to express the genes styAB encoding the Styrene monooxygenase of Pseudomonas sp. strain VLB120 from an expression plasmid utilizing the alk regulatory system of P. oleovorans GPo1. The strains reached specific activities of up to 70 U* (g cell dry weight)(-1) in shake-flask experiments with glucose as the carbon source. An efficient two-liquid phase fed-batch process was established for the production of (S)-Styrene Oxide with hexadecane as an apolar carrier solvent and a nutrient feed consisting of glucose, magnesium sulfate, and yeast extract. Engineering of the phase fraction and the composition of organic phase and feed led to a 2-L scale process with maximal volumetric productivities of 2.2 g (S)-Styrene Oxide per liter liquid volume per hour. This optimized process was based completely on defined medium and used bis(2-ethylhexyl)phthalate as the apolar carrier solvent, which together with substrate and inducer consisted of 50% of the total liquid volume. Using this system, we were able to produce per liter liquid volume 11 g of enantiopure (S)-Styrene Oxide in 10 h.
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towards a biocatalyst for s Styrene Oxide production characterization of the Styrene degradation pathway of pseudomonas sp strain vlb120
Applied and Environmental Microbiology, 1998Co-Authors: Sven Panke, Bernard Witholt, Andreas Schmid, Marcel WubboltsAbstract:In order to design a biocatalyst for the production of optically pure Styrene Oxide, an important building block in organic synthesis, the metabolic pathway and molecular biology of Styrene degradation in Pseudomonas sp. strain VLB120 was investigated. A 5.7-kb XhoI fragment, which contained on the same strand of DNA six genes involved in Styrene degradation, was isolated from a gene library of this organism in Escherichia coli by screening for indigo formation. T7 RNA polymerase expression experiments indicated that this fragment coded for at least five complete polypeptides, StyRABCD, corresponding to five of the six genes. The first two genes encoded the potential carboxy-terminal part of a sensor, named StySc, and the complete response regulator StyR. Fusion of the putative styAp promoter to a lacZ reporter indicated that StySc and StyR together regulate expression of the structural genes at the transcriptional level. Expression of styScR also alleviated a block that prevented translation of styA mRNA when a heterologous promoter was used. The structural genes styA and styB produced a Styrene monooxygenase that converted Styrene to Styrene Oxide, which was then converted to phenylacetaldehyde by StyC. Sequence homology analysis of StyD indicated a probable function as a phenylacetaldehyde dehydrogenase. To assess the usefulness of the enzymes for the production of enantiomerically pure Styrene Oxide, we investigated the enantiospecificities of the reactions involved. Kinetic resolution of racemic Styrene Oxide by Styrene Oxide isomerase was studied with E. coli recombinants carrying styC, which converted Styrene Oxide at a very high rate but with only a slight preference for the S enantiomer. However, recombinants producing Styrene monooxygenase catalyzed the formation of (S)-Styrene Oxide from inexpensive Styrene with an excellent enantiomeric excess of more than 99% at rates up to 180 U g (dry weight) of cells-1.
Bernard Witholt - One of the best experts on this subject based on the ideXlab platform.
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Enantioselective hydrolysis of Styrene Oxide with the epOxide hydrolase of Sphingomonas sp. HXN-200
Tetrahedron: Asymmetry, 2006Co-Authors: Zeya Liu, Johannes Michel, Zunsheng Wang, Bernard WitholtAbstract:Abstract The soluble bacterial epOxide hydrolase (EH) from Sphingomonas sp. HXN-200 catalyzed the enantioselective hydrolysis of racemic Styrene Oxide to give ( S )-Styrene Oxide with an enantiomeric ratio ( E ) of 21–23 in aqueous buffer, better than any reported native EHs. The ring opening of the Styrene Oxide with this EH was only at the terminal position for the ( S )-enantiomer and at the terminal and benzylic position in an 87:13 ratio for the ( R )-enantiomer. Enzymatic hydrolysis of the Styrene Oxide in a two-liquid phase system significantly reduced autohydrolysis, thus improving the E to 26–29. Hydrolysis of 160 mM Styrene Oxide with cell-free extract (CFE) of Sphingomonas sp. HXN-200 (10 mg protein/mL) in aqueous buffer and n -hexane (1:1) for 30.7 h afforded 39.2% (62.7 mM) of ( S )-Styrene Oxide in >99.9% ee. The lyophilized CFE was proven to be stable, while the rehydrated lyophilized CFE powder was successfully used for the hydrolysis of 320 mM Styrene Oxide in the two-liquid phase system, yielding 40.2% (128.6 mM) of ( S )-Styrene Oxide in >99.9% ee after 13.8 h. No inhibitory effect of the diol product on the hydrolysis was observed when the diol concentration was lower than 476 mM, suggesting a straightforward process for the hydrolysis of up to 1 M Styrene Oxide.
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production of enantiopure Styrene Oxide by recombinant escherichia coli synthesizing a two component Styrene monooxygenase
Biotechnology and Bioengineering, 2000Co-Authors: Sven Panke, Marcel Wubbolts, Andreas Schmid, Bernard WitholtAbstract:A whole cell biocatalytic process was developed to enable the efficient oxidation of Styrene to chiral (S)-Styrene Oxide with an enantiomeric excess better than 99%. Recombinant Escherichia coli cells were employed to express the genes styAB encoding the Styrene monooxygenase of Pseudomonas sp. strain VLB120 from an expression plasmid utilizing the alk regulatory system of P. oleovorans GPo1. The strains reached specific activities of up to 70 U* (g cell dry weight)(-1) in shake-flask experiments with glucose as the carbon source. An efficient two-liquid phase fed-batch process was established for the production of (S)-Styrene Oxide with hexadecane as an apolar carrier solvent and a nutrient feed consisting of glucose, magnesium sulfate, and yeast extract. Engineering of the phase fraction and the composition of organic phase and feed led to a 2-L scale process with maximal volumetric productivities of 2.2 g (S)-Styrene Oxide per liter liquid volume per hour. This optimized process was based completely on defined medium and used bis(2-ethylhexyl)phthalate as the apolar carrier solvent, which together with substrate and inducer consisted of 50% of the total liquid volume. Using this system, we were able to produce per liter liquid volume 11 g of enantiopure (S)-Styrene Oxide in 10 h.
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towards a biocatalyst for s Styrene Oxide production characterization of the Styrene degradation pathway of pseudomonas sp strain vlb120
Applied and Environmental Microbiology, 1998Co-Authors: Sven Panke, Bernard Witholt, Andreas Schmid, Marcel WubboltsAbstract:In order to design a biocatalyst for the production of optically pure Styrene Oxide, an important building block in organic synthesis, the metabolic pathway and molecular biology of Styrene degradation in Pseudomonas sp. strain VLB120 was investigated. A 5.7-kb XhoI fragment, which contained on the same strand of DNA six genes involved in Styrene degradation, was isolated from a gene library of this organism in Escherichia coli by screening for indigo formation. T7 RNA polymerase expression experiments indicated that this fragment coded for at least five complete polypeptides, StyRABCD, corresponding to five of the six genes. The first two genes encoded the potential carboxy-terminal part of a sensor, named StySc, and the complete response regulator StyR. Fusion of the putative styAp promoter to a lacZ reporter indicated that StySc and StyR together regulate expression of the structural genes at the transcriptional level. Expression of styScR also alleviated a block that prevented translation of styA mRNA when a heterologous promoter was used. The structural genes styA and styB produced a Styrene monooxygenase that converted Styrene to Styrene Oxide, which was then converted to phenylacetaldehyde by StyC. Sequence homology analysis of StyD indicated a probable function as a phenylacetaldehyde dehydrogenase. To assess the usefulness of the enzymes for the production of enantiomerically pure Styrene Oxide, we investigated the enantiospecificities of the reactions involved. Kinetic resolution of racemic Styrene Oxide by Styrene Oxide isomerase was studied with E. coli recombinants carrying styC, which converted Styrene Oxide at a very high rate but with only a slight preference for the S enantiomer. However, recombinants producing Styrene monooxygenase catalyzed the formation of (S)-Styrene Oxide from inexpensive Styrene with an excellent enantiomeric excess of more than 99% at rates up to 180 U g (dry weight) of cells-1.
