The Experts below are selected from a list of 9540 Experts worldwide ranked by ideXlab platform
Alexander Steinbüchel - One of the best experts on this subject based on the ideXlab platform.
-
Production of poly(4-Hydroxybutyric Acid) by fed-batch cultures of recombinant strains of Escherichia coli
Biotechnology Letters, 1999Co-Authors: Shuishan Song, Silke Hein, Alexander SteinbüchelAbstract:A recombinant strain of Escherichia coli was used to produce poly(4-Hydroxybutyric Acid), P(4HB), homopolyester by fed-batch culture in M9 mineral salts medium containing glucose and 4-Hydroxybutyric Acid as carbon sources. The final cell dry weight, P(4HB) concentration and P(4HB) content were 12.6 g/l, 4.4 g/l, and 36% of cell dry weight, respectively, in a 27-l stirred and aerated fermenter after 60 h of fed-batch fermentation at constant pH.
-
In vitro synthesis of poly(3-Hydroxybutyric Acid) by using an enzymatic coenzyme A recycling system
FEMS microbiology letters, 1998Co-Authors: Ralf Jossek, Alexander SteinbüchelAbstract:Purified recombinant poly(hydroxyalkanoic Acid), PHA, synthase from Chromatium vinosum was used to examine in vitro poly(3-Hydroxybutyric Acid) (P(3HB)) formation. In combination with purified propionyl-coenzyme A transferase of Clostridium propionicum a two-enzyme in vitro P(3HB) biosynthesis system was established which allowed the synthesis of P(3HB) from free d-(−)-3-Hydroxybutyric Acid as substrate. The coenzyme A residue for the activation of this hydroxyAcid was provided by acetyl-coenzyme A. By adding acetyl-coenzyme A synthetase to this system, a three-enzyme in vitro P(3HB) biosynthesis system was established. Coenzyme A that was released during the polymerization reaction was coupled to acetate which again served as the coenzyme A donor for the activation of 3-Hydroxybutyric Acid. The energy for the in vitro P(3HB) synthesis was provided by ATP hydrolyses resulting in acetyl-coenzyme A synthesis catalyzed by the acetyl coenzyme A synthetase. In this way the in vitro synthesis of P(3HB) became independent of the consumption of the expensive coenzyme A. By this procedure a handy system is available to produce in vitro PHA on a semipreparative scale.
-
Biosynthesis of poly(4-Hydroxybutyric Acid) by recombinant strains of Escherichia coli
FEMS microbiology letters, 1997Co-Authors: Silke Hein, Brigitte Söhling, Gerhard Gottschalk, Alexander SteinbüchelAbstract:The aim of this study was the production of the homopolyester poly(4-Hydroxybutyric Acid) (poly(4HB)) with recombinant strains of Escherichia coli. Wild-type strains and other widely used non-recombinant strains of E. coli are not able to produce polyhydroxyalkanoic Acids (PHA) as storage compounds and cannot utilize 4-Hydroxybutyric Acid as sole carbon source. Accordingly, hybrid plasmids of pBluescript vectors were constructed which harbored the Alcaligenes eutrophus PHA synthase gene (phaC) and the Clostridium kluyveri orfZ putatively encoding a 4-Hydroxybutyric Acid-coenzyme A transferase. A 3.5-kb genomic SmaI/ApaI fragment from A. eutrophus, which comprises phaC, and a 1.8-kb genomic ApaI/EcoRI fragment from C. kluyveri, which contained orfZ, were inserted into the SmaI and EcoRI sites of the vectors pKS− and pSK−, respectively. The two resulting plasmids pSKSE5.3 and pKSSE5.3 comprising phaC and orfZ colinear or antilinear to lacZ, respectively, were transformed into E. coli XL1-Blue. Recombinant strains synthesized the homopolyester poly(4HB), when the cells were cultivated in Luria-Bertani broth and if glucose and 4-Hydroxybutyric Acid were provided as carbon sources. If glucose was omitted, a copolyester of 3-Hydroxybutyric Acid and 4-Hydroxybutyric Acid was accumulated. The homopolyester poly(4HB) was also accumulated during cultivation of these strains in M9 mineral salts medium containing glucose plus 4-Hydroxybutyric Acid as carbon sources. Poly(4HB) could amount up to approximately 80% (w/w) of the cell dry matter if E. coli XL1-Blue harboring pKSSE5.3 was cultivated in M9 mineral salts medium and if the cultures were not sufficiently supplied with oxygen. 4HB was also incorporated into PHA if γ-butyrolactone was used as carbon source. If levulinic Acid, 4-hydroxyvaleric Acid or γ-valerolactone were used as carbon sources, only very low amounts of PHA were accumulated which did not contain 4-hydroxyalkanoic Acids as constituents.
-
Incorporation of 2-methyl-3-Hydroxybutyric Acid into polyhydroxyalkanoic Acids by axenic cultures in defined media
FEMS Microbiology Letters, 1996Co-Authors: Bernd Füchtenbusch, Dirk Fabritius, Alexander SteinbüchelAbstract:Alcaligenes eutrophus and Burkholderia cepacia synthesized and accumulated a terpolyester consisting of 3-Hydroxybutyric Acid, 3-hydroxyvaleric Acid, and 2-methyl-3-Hydroxybutyric Acid (2Me3HB) if the cells were cultivated in a mineral salts medium containing tiglic Acid as the sole carbon source or in combination with gluconic Acid. The presence of 1–2 mol% of 2Me3HB in the polyester was confirmed by comparison with chemically synthesized methyl ester of 2Me3HB and by nuclear magnetic resonance spectrometry as well as by gas chromatography/mass spectrometry. This is the first report of the incorporation of 2Me3HB by axenic cultures cultivated under defined conditions.
-
Application of recombinant gene technology for production of polyhydroxyalkanoic Acids: Biosynthesis of poly(4-Hydroxybutyric Acid) homopolyester
Journal of Environmental Polymer Degradation, 1994Co-Authors: Alexander Steinbüchel, Henry E. Valentin, Andreas SchönebaumAbstract:Screening of a large number of bacteria revealed several strains, which utilize 1,4-butanediol and/or 4-Hydroxybutyric Acid (4HB) as a carbon source for growth and for synthesis of polyhydroxyalkanoic Acids (PHA) containing 4HB as one constituent among others (mostly 3-Hydroxybutyric Acid). However, none of the wild-type strains investigated in this study was able to produce a homopolyester consisting solely of 4HB. Only several poly(3-Hydroxybutyric Acid)-leaky mutants ofAlcaligenes eutrophus strain JMP222 synthesized poly(4HB) homopolyester, which amounted to approximately 10% (w/w) of the cellular dry matter. If the PHA synthase structural gene ofA. eutrophus strain H16 was expressed in these mutants, the amount of poly(4HB) was increased to approximately 30% (w/w). The occurrence of poly(4HB) was demonstrated by gas chromatographic as well as1H and13C nuclear magnetic resonance spectroscopic analysis.
Gian Luigi Gessa - One of the best experts on this subject based on the ideXlab platform.
-
Protection by the GABAB receptor antagonist, SCH 50911, of gamma-Hydroxybutyric Acid-induced mortality in mice.
European journal of pharmacology, 2004Co-Authors: Mauro A.m. Carai, Giancarlo Colombo, Gian Luigi GessaAbstract:Different effects of moderate to high doses of gamma-Hydroxybutyric Acid, including sedation/hypnosis, have been found to be blocked by gamma-aminobutyric AcidB (GABAB) receptor antagonists. The present study investigated whether the protective effect of GABAB receptor antagonists extends also to gamma-Hydroxybutyric Acid-induced mortality. To this aim, the present study investigated the effect of the GABAB receptor antagonist, (2S)(+)-5,5-dimethyl-2-morpholineacetic Acid (SCH 50911; 100 mg/kg, ip), on mortality induced by gamma-Hydroxybutyric Acid (1-6 g/kg, ip) in DBA mice. Pretreatment with SCH 50911 resulted in a significant shift to the right of the dose-response curve of gamma-Hydroxybutyric Acid-induced mortality. Accordingly, the LD50 in SCH 50911-pretreated mice was significantly higher than that obtained in water-pretreated mice. The results of the present study support the hypothesis that (a) the GABAB receptor is a relevant site of action of gamma-Hydroxybutyric Acid, and (b) GABAB receptor antagonists may constitute potentially effective therapeutic interventions for gamma-Hydroxybutyric Acid intoxication.
-
Protection by the GABAB receptor antagonist, SCH 50911, of γ-Hydroxybutyric Acid-induced mortality in mice
European Journal of Pharmacology, 2004Co-Authors: Mauro A.m. Carai, Giancarlo Colombo, Gian Luigi GessaAbstract:Abstract Different effects of moderate to high doses of γ-Hydroxybutyric Acid, including sedation/hypnosis, have been found to be blocked by γ-aminobutyric Acid B (GABA B ) receptor antagonists. The present study investigated whether the protective effect of GABA B receptor antagonists extends also to γ-Hydroxybutyric Acid-induced mortality. To this aim, the present study investigated the effect of the GABA B receptor antagonist, (2S)(+)-5,5-dimethyl-2-morpholineacetic Acid (SCH 50911; 100 mg/kg, ip), on mortality induced by γ-Hydroxybutyric Acid (1–6 g/kg, ip) in DBA mice. Pretreatment with SCH 50911 resulted in a significant shift to the right of the dose–response curve of γ-Hydroxybutyric Acid-induced mortality. Accordingly, the LD 50 in SCH 50911-pretreated mice was significantly higher than that obtained in water-pretreated mice. The results of the present study support the hypothesis that (a) the GABA B receptor is a relevant site of action of γ-Hydroxybutyric Acid, and (b) GABA B receptor antagonists may constitute potentially effective therapeutic interventions for γ-Hydroxybutyric Acid intoxication.
-
Characterization of the discriminative stimulus effects of gamma-Hydroxybutyric Acid as a means for unraveling the neurochemical basis of gamma-Hydroxybutyric Acid actions and its similarities to those of ethanol☆
Alcohol (Fayetteville N.Y.), 2000Co-Authors: Giancarlo Colombo, Roberta Agabio, Mauro A.m. Carai, Carla Lobina, Marialaura Pani, Roberta Reali, Gian Luigi GessaAbstract:The present paper reviews the drug discrimination studies, both from the literature and from this laboratory, conducted to investigate the pharmacological profile of the discriminative stimulus effects of gamma-Hydroxybutyric Acid. Collectively, the results of these studies suggest that: (1) the discriminative stimulus effects of gamma-Hydroxybutyric Acid are composed of different cues, each one being the effect of gamma-Hydroxybutyric Acid on a specific receptor system; (2) the proportion of each component cue varies as the training dose of gamma-Hydroxybutyric Acid is increased; (3) the gamma-aminobutyric Acid B-mediated cue is a major ingredient of the mixed stimulus of gamma-Hydroxybutyric Acid, but it is more prominent at high training doses than at low training doses of gamma-Hydroxybutyric Acid; and (4) positive modulation of the gamma-aminobutyric Acid A receptor is a relevant part of the discriminative stimulus effects of low gamma-Hydroxybutyric Acid doses. Finally, data indicating symmetrical generalization between the discriminative stimulus effects of a specific range of doses of gamma-Hydroxybutyric Acid and those of ethanol are discussed in regard to their further support of the hypothesis that gamma-Hydroxybutyric Acid may exert its antialcohol effects through a substitution mechanism.
-
Mechanism of the antialcohol effect of gamma-Hydroxybutyric Acid.
Alcohol (Fayetteville N.Y.), 2000Co-Authors: Gian Luigi Gessa, Roberta Agabio, Mauro A.m. Carai, Carla Lobina, Marialaura Pani, Roberta Reali, Giancarlo ColomboAbstract:Treatment with gamma-Hydroxybutyric Acid has been reported to effectively decrease alcohol craving and consumption as well as alcohol withdrawal symptoms in alcoholics. We describe the results of animal studies demonstrating the ability of gamma-Hydroxybutyric Acid to reduce (1) the severity of ethanol withdrawal signs in rats rendered physically dependent on ethanol and (2) voluntary ethanol intake in selectively bred Sardinian alcohol-preferring rats. Furthermore, we review experimental data suggesting that gamma-Hydroxybutyric Acid and ethanol have several pharmacological effects in common. Relevant similarities are: (1) stimulation of firing rate of dopaminergic neurons and dopamine release in specific rat brain areas; (2) development of cross-tolerance to the motor-impairing effects after repeated administration in rats; 3) abuse potential, as indicated by self-administration of pharmacologically relevant doses of gamma-Hydroxybutyric Acid in rats and mice; (4) induction of anxiolytic effects in rats; and (5) induction of similar discriminative stimulus effects, as evidenced by symmetrical generalization in a drug discrimination study in rats. These lines of evidence are discussed in relation to gamma-Hydroxybutyric Acid exerting its antialcohol effects by a substitution mechanism.
-
Gamma-Hydroxybutyric Acid in the treatment of alcohol and heroin dependence.
Alcohol (Fayetteville N.Y.), 2000Co-Authors: Luigi Gallimberti, Maurizio Raffaele Spella, Carlo Alberto Soncini, Gian Luigi GessaAbstract:We briefly review two double-blind, placebo-controlled surveys conducted in this laboratory with the aim of evaluating the efficacy of gamma-Hydroxybutyric Acid in the treatment of alcohol withdrawal syndrome as well as alcohol craving and consumption in alcoholics. In the first study, acute administration of 50 mg/kg gamma-Hydroxybutyric Acid, a nonhypnotic dose in alcoholic patients, resulted in a rapid and significant reduction of the severity score of alcohol withdrawal signs and symptoms that lasted as long as 7 hours. In the second study, treatment with 50 mg/kg/day gamma-Hydroxybutyric Acid for 3 consecutive months (1) reduced the number of daily drinks by approximately 50%, (2) increased the days of abstinence approximately threefold, and (3) reduced the alcohol craving score by up to 60%. These results feature gamma-Hydroxybutyric Acid as an effective agent for the treatment of alcohol dependence. Data on the effect of gamma-Hydroxybutyric Acid on opiate withdrawal syndrome also are reviewed. Administration of 25 mg/kg induced a marked reduction of opiate withdrawal score in both heroin- and methadone-dependent subjects. Finally, we report the cases of adverse reactions to and abuse of gamma-Hydroxybutyric Acid revealed in a retrospective analysis of patients recruited in this laboratory over a 10-year period.
Hideki Abe - One of the best experts on this subject based on the ideXlab platform.
-
Adsorption and hydrolysis reactions of poly(Hydroxybutyric Acid) depolymerases secreted from Ralstonia pickettii T1 and Penicillium funiculosum onto poly[(R)-3-Hydroxybutyric Acid].
Biomacromolecules, 2007Co-Authors: Keiji Numata, Koichi Yamashita, Masahiro Fujita, Takeharu Tsuge, Ken-ichi Kasuya, Tadahisa Iwata, Yoshiharu Doi, Hideki AbeAbstract:Reaction processes of poly[(R)-3-Hydroxybutyric Acid] (P(3HB)) with two types of poly(Hydroxybutyric Acid) (PHB) depolymerases secreted from Ralstonia pickettii T1 and Penicillium funiculosum were characterized by means of atomic force microscopy (AFM) and quartz crystal microbalance (QCM). The PHB depolymerase from R. pickettii T1 consists of catalytic, linker, and substrate-binding domains, whereas the one from P. funiculosum lacks a substrate-binding domain. We succeeded in observing the adsorption of single molecules of the PHB depolymerase from R. pickettii T1 onto P(3HB) single crystals and the degradation of the single crystals in a phosphate buffer solution at 37 °C by real-time AFM. On the contrary, the enzyme molecule from P. funiculosum was hardly observed at the surface of P(3HB) single crystals by real-time AFM, even though the enzymatic degradation of the single crystals was surely progressed. On the basis of the AFM observations in air of the P(3HB) single crystals after the enzymatic treat...
-
effects of residual metal compounds and chain end structure on thermal degradation of poly 3 Hydroxybutyric Acid
Polymer Degradation and Stability, 2006Co-Authors: Kang Ju Kim, Yoshiharu Doi, Hideki AbeAbstract:Abstract Thermal degradation behaviours of poly(3-Hydroxybutyric Acid) (P(3HB); bacterial poly[( R )-3-Hydroxybutyric Acid] and synthetic poly[( R , S )-3-Hydroxybutyric Acid] samples, were examined under both isothermal and non-isothermal conditions. The inverse of number-average degree of polymerisation for all P(3HB) samples decreased linearly with degradation time during the initial stage of isothermal degradation at a temperature ranging from 170–190 °C. In addition, crotonyl unit was detected in the residual polymer samples as main ω-chain-end. These results indicate that the dominant thermal degradation reaction for P(3HB) is a random chain scission via cis -elimination reaction of P(3HB) molecules. It was found that the presence of either Ca or Mg ions enhances the depolymerisation of P(3HB) molecules, while that Zn ions hardly catalyse the reaction. As a result, a shift of thermogravimetric curves toward the lower temperature regions was observed for the P(3HB) samples containing high amounts of Ca and Mg compounds.
Ulrich W. Suter - One of the best experts on this subject based on the ideXlab platform.
-
telechelic diols from poly r 3 Hydroxybutyric Acid and poly r 3 Hydroxybutyric Acid co r 3 hydroxyvaleric Acid
Macromolecular Chemistry and Physics, 1996Co-Authors: T. Hirt, Peter Neuenschwander, Ulrich W. SuterAbstract:We describe the preparation of telechelic OH-terminated poly[(R)-3-Hydroxybutyric Acid] (PHB) and poly{[(R)-3-Hydroxybutyric Acid]-co-[(R)-3-hydroxyvaleric Acid]} (PHB/HV), on a semi-preparative scale, by a transesterification procedure from the high-molecular weight polymers. The oligomers have well-defined reactive end groups and are well suited for the preparation of high-molecular-weight block copolymers by chain extension.
-
Telechelic diols from poly[(R)-3-Hydroxybutyric Acid] and poly{[(R)-3-Hydroxybutyric Acid]-co-[(R)-3-hydroxyvaleric Acid]}
Macromolecular Chemistry and Physics, 1996Co-Authors: T. Hirt, Peter Neuenschwander, Ulrich W. SuterAbstract:We describe the preparation of telechelic OH-terminated poly[(R)-3-Hydroxybutyric Acid] (PHB) and poly{[(R)-3-Hydroxybutyric Acid]-co-[(R)-3-hydroxyvaleric Acid]} (PHB/HV), on a semi-preparative scale, by a transesterification procedure from the high-molecular weight polymers. The oligomers have well-defined reactive end groups and are well suited for the preparation of high-molecular-weight block copolymers by chain extension.
Robert W. Lenz - One of the best experts on this subject based on the ideXlab platform.
-
Production of poly(3-Hydroxybutyric Acid-co-4-Hydroxybutyric Acid) and poly(4-Hydroxybutyric Acid) without subsequent degradation by Hydrogenophaga pseudoflava.
Applied and environmental microbiology, 1999Co-Authors: Mun Hwan Choi, Sung Chul Yoon, Robert W. LenzAbstract:A Hydrogenophaga pseudoflava strain was able to synthesize poly(3-Hydroxybutyric Acid-co-4-Hydroxybutyric Acid) [P(3HB-co-4HB)] having a high level of 4-Hydroxybutyric Acid monomer unit (4HB) from γ-butyrolactone. In a two-step process in which the first step involved production of cells containing a minimum amount of poly(3-Hydroxybutyric Acid) [P(3HB)] and the second step involved polyester accumulation from the lactone, approximately 5 to 10 mol% of the 3-Hydroxybutyric Acid (3HB) derived from the first-step culture was unavoidably reincorporated into the polymer in the second cultivation step. Reincorporation of the 3HB units produced from degradation of the first-step residual P(3HB) was confirmed by high-resolution 13C nuclear magnetic resonance spectroscopy. In order to synthesize 3HB-free poly(4-Hydroxybutyric Acid) [P(4HB)] homopolymer, a three-stage cultivation technique was developed by adding a nitrogen addition step, which completely removed the residual P(3HB). The resulting polymer was free of 3HB. However, when the strain was grown on γ-butyrolactone as the sole carbon source in a synthesis medium, a copolyester of P(3HB-co-4HB) containing 45 mol% 3HB was produced. One-step cultivation on γ-butyrolactone required a rather long induction time (3 to 4 days). On the basis of the results of an enzymatic study performed with crude extracts, we suggest that the inability of cells to produce 3HB in the multistep culture was due to a low level of 4-Hydroxybutyric Acid (4HBA) dehydrogenase activity, which resulted in a low level of acetyl coenzyme A. Thus, 3HB formation from γ-butyrolactone is driven by a high level of 4HBA dehydrogenase activity induced by long exposure to γ-butyrolactone, as is the case for a one-step culture. In addition, intracellular degradation kinetics studies showed that P(3HB) in cells was completely degraded within 30 h of cultivation after being transferred to a carbon-free mineral medium containing additional ammonium sulfate, while P(3HB-co-4HB) containing 5 mol% 3HB and 95 mol% 4HB was totally inert in interactions with the intracellular depolymerases. Intracellular inertness could be a useful factor for efficient synthesis of the P(4HB) homopolymer and of 4HB-rich P(3HB-co-4HB) by the strain used in this study.
