Filters

2020 - 20224

More filters

2022 - 20234
Reset filters

Settings

Author: Mikolasch, Annett × End date: 2024 × Start date: 2020 × Type: Text ×

Search Results

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Ring-Closure Mechanisms Mediated by Laccase to Synthesize Phenothiazines, Phenoxazines, and Phenazines
    (Washington, DC : ACS Publications, 2020) Hahn, Veronika; Mikolasch, Annett; Weitemeyer, Josephine; Petters, Sebastian; Davids, Timo; Lalk, Michael; Lackmann, Jan-Wilm; Schauer, Frieder
    The green and environmentally friendly synthesis of highly valuable organic substances is one possibility for the utilization of laccases (EC 1.10.3.2). As reactants for the herein described syntheses, different o-substituted arylamines or arylthiols and 2,5-dihydroxybenzoic acid and its derivatives were used. In this way, the formation of phenothiazines, phenoxazines, and phenazines was achieved in aqueous solution mediated by the laccase of Pycnoporus cinnabarinus in the presence of oxygen. Two types of phenothiazines (3-hydroxy- and 3-oxo-phenothiazines) formed in one reaction assay were described for the first time. The cyclization reactions yielded C–N, C–S, or C–O bonds. The syntheses were investigated with regard to the substitution pattern of the reaction partners. Differences in C–S and C–N bond formations without cyclization are discussed.
  • Thumbnail Image
    Item
    Laccase‐Catalyzed Derivatization of Aminoglycoside Antibiotics and Glucosamine
    (Basel : MDPI, 2022) Mikolasch, Annett; Lindequist, Ulrike; Witt, Sabine; Hahn, Veronika
    The increasing demand for new and effective antibiotics requires intelligent strategies to obtain a wide range of potential candidates. Laccase‐catalyzed reactions have been successfully applied to synthesize new β‐lactam antibiotics and other antibiotics. In this work, laccases from three different origins were used to produce new aminoglycoside antibiotics. Kanamycin, tobramycin and gentamicin were coupled with the laccase substrate 2,5‐dihydroxy‐N‐(2‐hydroxyethyl)‐benzamide. The products were isolated, structurally characterized and tested in vitro for antibacterial activity against various strains of Staphylococci, including multidrug‐resistant strains. The cytotoxicity of these products was tested using FL cells. The coupling products showed comparable and, in some cases, better antibacterial activity than the parent antibiotics in the agar diffusion assay, and they were not cytotoxic. The products protected mice against infection with Staphylococcus aureus, which was lethal to the control animals. The results underline the great potential of laccases in obtaining new biologically active compounds, in this case new antibiotic candidates from the class of aminoglycosides.
  • Thumbnail Image
    Item
    Moniliella spathulata, an oil-degrading yeast, which promotes growth of barley in oil-polluted soil
    (Berlin ; Heidelberg ; New York : Springer, 2021) Mikolasch, Annett; Berzhanova, Ramza; Omirbekova, Anel; Reinhard, Anne; Zühlke, Daniele; Meister, Mareike; Mukasheva, Togzhan; Riedel, Katharina; Urich, Tim; Schauer, Frieder
    The yeast strain Moniliella spathulata SBUG-Y 2180 was isolated from oil-contaminated soil at the Tengiz oil field in the Atyrau region of Kazakhstan on the basis of its unique ability to use crude oil and its components as the sole carbon and energy source. This yeast used a large number of hydrocarbons as substrates (more than 150), including n-alkanes with chain lengths ranging from C10 to C32, monomethyl- and monoethyl-substituted alkanes (C9–C23), and n-alkylcyclo alkanes with alkyl chain lengths from 3 to 24 carbon atoms as well as substituted monoaromatic and diaromatic hydrocarbons. Metabolism of this huge range of hydrocarbon substrates produced a very large number of aliphatic, alicyclic, and aromatic acids. Fifty-one of these were identified by GC/MS analyses. This is the first report of the degradation and formation of such a large number of compounds by a yeast. Inoculation of barley seeds with M. spathulata SBUG-Y 2180 had a positive effect on shoot and root development of plants grown in oil-contaminated sand, pointing toward potential applications of the yeast in bioremediation of polluted soils. Key points: • Moniliella spathulata an oil-degrading yeast • Increase of the growth of barley. © 2020, The Author(s).
  • Thumbnail Image
    Item
    Laccase-catalyzed derivatization of antibiotics with sulfonamide or sulfone structures
    (Basel : MDPI, 2021) Mikolasch, Annett; Hahn, Veronika
    Trametes spec. laccase (EC 1.10.3.2.) mediates the oxidative coupling of antibiotics with sulfonamide or sulfone structures with 2,5-dihydroxybenzene derivatives to form new heterodimers and heterotrimers. These heteromolecular hybrid products are formed by nuclear amination of the p-hydroquinones with the primary amino group of the sulfonamide or sulfone antibiotics, and they inhibited in vitro the growth of Staphylococcus species, including multidrug-resistant strains.