8 results on '"Lalk M"'
Search Results
2. Biotransformation of bisphenol A analogues by the biphenyl-degrading bacterium Cupriavidusbasilensis - a structure-biotransformation relationship.
- Author
-
Zühlke MK, Schlüter R, Mikolasch A, Henning AK, Giersberg M, Lalk M, Kunze G, Schweder T, Urich T, and Schauer F
- Subjects
- Benzhydryl Compounds classification, Cyclohexanes metabolism, Phenols metabolism, Soil Microbiology, Structure-Activity Relationship, Tandem Mass Spectrometry, Benzhydryl Compounds metabolism, Biotransformation, Cupriavidus metabolism
- Abstract
Comparative analyses determined the relationship between the structure of bisphenol A (BPA) as well as of seven bisphenol analogues (bisphenol B (BPB), bisphenol C (BPC), bisphenol E (BPE), bisphenol F (BPF), bisphenol Z (BPZ), bisphenol AP (BPAP), bisphenol PH (BPPH)) and their biotransformability by the biphenyl-degrading bacterium Cupriavidus basilensis SBUG 290. All bisphenols were substrates for bacterial transformation with conversion rates ranging from 6 to 98% within 216 h and 36 different metabolites were characterized. Transformation by biphenyl-grown cells comprised four different pathways: (a) formation of ortho-hydroxylated bisphenols, hydroxylating either one or both phenols of the compounds; (b) ring fission; (c) transamination followed by acetylation or dimerization; and (d) oxidation of ring substituents, such as methyl groups and aromatic ring systems, present on the 3-position. However, the microbial attack of bisphenols by C. basilensis was limited to the phenol rings and its substituents, while substituents on the carbon bridge connecting the rings were not oxidized. All bisphenol analogues with modifications at the carbon bridge could be oxidized up to ring cleavage, while substituents at the 3-position of the phenol ring other than hydroxyl groups did not allow this reaction. Replacing one methyl group at the carbon bridge of BPA by a hydrophobic aromatic or alicyclic ring system inhibited both dimerization and transamination followed by acetylation. While most of the bisphenol analogues exhibited estrogenic activity, four biotransformation products tested were not estrogenically active.
- Published
- 2020
- Full Text
- View/download PDF
3. Biotransformation and reduction of estrogenicity of bisphenol A by the biphenyl-degrading Cupriavidus basilensis.
- Author
-
Zühlke MK, Schlüter R, Mikolasch A, Zühlke D, Giersberg M, Schindler H, Henning AK, Frenzel H, Hammer E, Lalk M, Bornscheuer UT, Riedel K, Kunze G, and Schauer F
- Subjects
- Biotransformation, Carbon metabolism, Cupriavidus growth & development, Metabolic Networks and Pathways, Benzhydryl Compounds metabolism, Cupriavidus metabolism, Estrogens, Non-Steroidal metabolism, Phenols metabolism
- Abstract
The biphenyl-degrading Gram-negative bacterium Cupriavidus basilensis (formerly Ralstonia sp.) SBUG 290 uses various aromatic compounds as carbon and energy sources and has a high capacity to transform bisphenol A (BPA), which is a hormonally active substance structurally related to biphenyl. Biphenyl-grown cells initially hydroxylated BPA and converted it to four additional products by using three different transformation pathways: (a) formation of multiple hydroxylated BPA, (b) ring fission, and (c) transamination followed by acetylation or dimerization. Products of the ring fission pathway were non-toxic and all five products exhibited a significantly reduced estrogenic activity compared to BPA. Cell cultivation with phenol and especially in nutrient broth (NB) resulted in a reduced biotransformation rate and lower product quantities, and NB-grown cells did not produce all five products in detectable amounts. Thus, the question arose whether enzymes of the biphenyl degradation pathway are involved in the transformation of BPA and was addressed by proteomic analyses.
- Published
- 2017
- Full Text
- View/download PDF
4. Production of the polyketide 6-deoxyerythronolide B in the heterologous host Bacillus subtilis.
- Author
-
Kumpfmüller J, Methling K, Fang L, Pfeifer BA, Lalk M, and Schweder T
- Subjects
- Bacterial Proteins genetics, Bacterial Proteins metabolism, Erythromycin biosynthesis, Metabolic Engineering, Saccharopolyspora enzymology, Saccharopolyspora genetics, Bacillus subtilis genetics, Bacillus subtilis metabolism, Erythromycin analogs & derivatives, Polyketides metabolism
- Abstract
Polyketides, such as erythromycin, are complex natural products with diverse therapeutic applications. They are synthesized by multi-modular megaenzymes, so-called polyketide synthases (PKSs). The macrolide core of erythromycin, 6-deoxyerythronolide B (6dEB), is produced by the deoxyerythronolide B synthase (DEBS) that consists of three proteins each with a size of 330-370 kDa. We cloned and investigated the expression of the corresponding gene cluster from Saccharopolyspora erythraea, which comprises more than 30 kb, in Bacillus subtilis. It is shown that the DEBS genes are functionally expressed in B. subtilis when the native eryAI-III operon was separated into three individual expression cassettes with optimized ribosomal binding sites. A synthesis of 6dEB could be detected by using the acetoin-inducible acoA promoter and a fed-batch simulating EnBase-cultivation strategy. B. subtilis was capable of the secretion of 6dEB into the medium. In order to improve the 6dEB production, several genomic modifications of this production strain were tested. This included the knockout of the native secondary metabolite clusters of B. subtilis for the synthesis of surfactin (26 kb), bacillaene (76 kb), and plipastatin (38 kb). It is revealed that the deletion of the prpBD operon, responsible for propionyl-CoA utilization, resulted in a significant increase of the 6dEB product yield when exogenous propionate is provided. Although the presented B. subtilis 6dEB production strain is not competitive with established Escherichia coli 6dEB production strains, the results of this study indicate that B. subtilis is a suitable heterologous host for the secretory production of a complex polyketide.
- Published
- 2016
- Full Text
- View/download PDF
5. Regulation of acetoin and 2,3-butanediol utilization in Bacillus licheniformis.
- Author
-
Thanh TN, Jürgen B, Bauch M, Liebeke M, Lalk M, Ehrenreich A, Evers S, Maurer KH, Antelmann H, Ernst F, Homuth G, Hecker M, and Schweder T
- Subjects
- Bacillus genetics, Bacterial Proteins genetics, Bacterial Proteins metabolism, Base Sequence, Molecular Sequence Data, Operon, Promoter Regions, Genetic, Acetoin metabolism, Bacillus metabolism, Butylene Glycols metabolism, Gene Expression Regulation, Bacterial
- Abstract
The acoABCL and acuABC operons of Bacillus licheniformis DSM13 are strongly induced at the transcriptional level during glucose starvation conditions. Primer extension analyses of this study indicate that the acoABCL operon is controlled by a sigmaL-dependent promoter and the acuABC operon by a sigmaA-dependent promoter. Transcription at the acoA promoter is repressed by glucose but induced by acetoin as soon as the preferred carbon source glucose is exhausted. The acuA promoter shows a similar induction pattern, but its activity is independent from the presence of acetoin. It is demonstrated that the acoABCL operon is mainly responsible for acetoin and 2,3-butanediol degradation in B. licheniformis.
- Published
- 2010
- Full Text
- View/download PDF
6. Chemical characterization of soil extract as growth media for the ecophysiological study of bacteria.
- Author
-
Liebeke M, Brözel VS, Hecker M, and Lalk M
- Subjects
- Bacillus metabolism, Gas Chromatography-Mass Spectrometry, Magnetic Resonance Spectroscopy, Metabolome, Culture Media chemistry, Gram-Negative Bacteria growth & development, Gram-Positive Bacteria growth & development, Inorganic Chemicals analysis, Organic Chemicals analysis, Soil analysis
- Abstract
We investigated the composition of soil-extracted solubilized organic and inorganic matter (SESOM) prepared from three different soils. Growth of various bacterial strains in these soil extracts was evaluated to find appropriate conditions for ecophysiological approaches. Analysis of SESOM by (1)H-NMR and gas chromatography/mass spectrometry revealed a complex mixture of organic compounds. An oak forest SESOM supported the growth of several gram-positive and gram-negative soil-derived heterotrophic bacteria, whereas beech forest and grassland soil extracts did not. A metabolomic approach was performed by determining the extracellular metabolite profile of Bacillus licheniformis in SESOM. The results demonstrated that determination of the organic composition of SESOM during batch culturing is feasible. This makes SESOM amenable to studying the ecophysiology of a range of soil bacteria growing on soil-dissolved organic matter under more defined laboratory conditions. SESOM may also increase success in isolating previously uncultured or novel soil bacteria. Cell populations and the corresponding extracellular medium can be obtained readily and specific components extracted, paving the way for proteomic, transcriptomic, and metabolomic analyses. The synthetic carbon mixture based on SESOM, which mimics soil abilities, shows a positive impact on higher cell yields and longer cultivation time for biotechnological relevant bacteria.
- Published
- 2009
- Full Text
- View/download PDF
7. Derivatization of bioactive carbazoles by the biphenyl-degrading bacterium Ralstonia sp. strain SBUG 290.
- Author
-
Waldau D, Mikolasch A, Lalk M, and Schauer F
- Subjects
- Biotransformation, Biphenyl Compounds metabolism, Chromatography, High Pressure Liquid, Chromatography, Liquid, Gas Chromatography-Mass Spectrometry, Iron-Sulfur Proteins biosynthesis, Magnetic Resonance Spectroscopy, Mass Spectrometry, Oxygenases biosynthesis, Ralstonia growth & development, Carbazoles metabolism, Ralstonia metabolism
- Abstract
Different 9H-carbazole derivatives have been investigated within the last decades due to their broad range of pharmacological applications. While the metabolism of 9H-carbazole has previously been reported, nothing was known about the bacterial transformation of 2,3,4,9-tetrahydro-1H-carbazole and 9-methyl-9H-carbazole. Thus, for the first time, the bacterial biotransformation of 2,3,4,9-tetrahydro-1H-carbazole and 9-methyl-9H-carbazole was analyzed using biphenyl-grown cells of Ralstonia sp. strain SBUG 290 expressing biphenyl 2,3-dioxygenase. This strain accumulated 3-hydroxy-1,2,3,5,6,7,8,9-octahydrocarbazol-4-one and 6'-iminobicyclohexylidene-2',4'-dien-2-one as major products during the incubation with 2,3,4,9-tetrahydro-1H-carbazole. Carbazol-9-yl-methanol was verified as the primary oxidation product of 9-methyl-9H-carbazole. In addition, 9H-carbazol-1-ol, 9H-carbazol-3-ol, and 3-hydroxy-1,2,3,9-tetrahydrocarbazol-4-one where detected in lower concentrations during the transformation of carbazol-9-yl-methanol and 9-methyl-9H-carbazole. Products were identified by high-performance liquid chromatography, gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, as well as (1)H and (13)C nuclear magnetic resonance analyses.
- Published
- 2009
- Full Text
- View/download PDF
8. Laccase-induced C-N coupling of substituted p-hydroquinones with p-aminobenzoic acid in comparison with known chemical routes.
- Author
-
Mikolasch A, Matthies A, Lalk M, and Schauer F
- Subjects
- 4-Aminobenzoic Acid chemistry, Fungal Proteins chemistry, Laccase chemistry, Substrate Specificity, 4-Aminobenzoic Acid metabolism, Fungal Proteins metabolism, Hydroquinones chemistry, Hydroquinones metabolism, Laccase metabolism, Polyporaceae enzymology
- Abstract
Fungal laccases (benzenediol:oxygen oxidoreductase, EC 1.10.3.2) from Pycnoporus cinnabarinus and Myceliophthora thermophila were used as biocatalysts for enzymatic reaction of halogen-, alkyl-, alkoxy-, and carbonyl-substituted p-hydroquinones (laccase substrates) with p-aminobenzoic acid (no laccase substrate). During this reaction, the laccase substrate was oxidized to the corresponding quinones, which react with p-aminobenzoic acid by amination of the laccase substrate. The different substitutions at the hydroquinone substrates were used to prove whether the substituents influence the position of amination and product yields. The cross-coupling of methoxy-p-hydroquinone (alkoxylated) and 2,5-dihydroxybenzaldehyd (carbonyl-substituted) with p-aminobenzoic acid resulted in the formation of one monoaminated product (yield alkoxylated 52%). If monohalogen- or monoalkyl-substituted p-hydroquinones were used as laccase substrates, two monoaminated products (constitution isomers) were formed. The simultaneous formation of two different monoaminated products from the same hydroquinone substrate is the first report for laccase-mediated synthesis of aminated constitution isomers. Depending from the type of substituent of the hydroquinone, the positions of the two monoaminations are different. While the amination at the monoalkylated hydroquinone occurs at the 5- and 6-positions (yield 38%), the amination at monohalogenated hydroquinones was detectable at the 3- and 5-positions (yield 53%). The same product pattern could be achieved if instead of the biocatalyst laccase the chemical catalyst sodium iodate was used as the oxidant. However, the yields were partially much lower (0-45% of the yields with laccase).
- Published
- 2008
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.