Search Results
Ring-Closure Mechanisms Mediated by Laccase to Synthesize Phenothiazines, Phenoxazines, and Phenazines
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.
Enhanced laccase-mediated transformation of diclofenac and flufenamic acid in the presence of bisphenol A and testing of an enzymatic membrane reactor
The inadequate removal of pharmaceuticals and other micropollutants in municipal wastewater treatment plants, as evidenced by their detection of these substances in the aquatic environment has led to the need for sustainable remediation strategies. Laccases possess a number of advantages including a broad substrate spectrum. To identify promoting or inhibitory effects of reaction partners in the remediation processes we tested not only single compounds-as has been described in most studies-but also mixtures of pollutants. The reaction of diclofenac (DCF) and flufenamic acid (FA), mediated by Trametes versicolor laccase resulted in the formation of products, which were more hydrophilic than the respective reactant (reactant concentration of 0.1 mM; laccase activity 0.5 U/ml). Analyses (HPLC, LC/MS) showed that the product 1a and 1b for DCF and FA, respectively, to be a para-benzoquinone imine derivative. The formation of 1a was enhanced by the addition of bisphenol A (BPA). After 6 days 97% more product was formed in the mixture of DCF and BPA compared with DCF tested alone. Product 1a was also detected in experiments with micropollutant-supplemented secondary effluent. Within 24 h 67% and 100% of DCF and BPA were transformed, respectively (25 U/ml). Experiments with a membrane reactor (volume 10 l; phosphate buffer, pH 7) were in good agreement with the results of the laboratory scale experiments (50 ml). EC50-values were also determined. The data support the use of laccases for the removal or detoxification of recalcitrant pollutants. Thus, the enzyme laccase may be a component of an additional environmentally friendly process for the treatment stage of wastewater remediation.
Moniliella spathulata, an oil-degrading yeast, which promotes growth of barley in oil-polluted soil
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).