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Abstract

The magnetostructural correlations in Fe(III) complexes, originally outlined by Gorun and Lippard has been revised. Other correlation variants have been tested and the dataset enlarged for more recent entries possessing the Fe-O-Fe bridge including dinuclear, tetranuclear and hexanuclear Fe(III) complexes. The resulting relationships confirm that instead of the original suggestions, the correlation could stay as a linear relationship which covers the possibilities of positive values of exchange coupling constants.

Abstract

The concentration of Eu(III) cations in model aqueous solutions can be quantified by means of Arsenazo III reagent. Absorbance of the solution was measured at the wavelength λmax = 655 nm. Molar absorptivity reached the value ε655 = 5.5±0.2 · 104 cm-1 mol-1 · dm3. Beer's law was obeyed in the range from 0 to 2 mg · dm-3 Eu(III). The value of limit of detection was established by application of 3σ approach and reached the value of 20.9 μg · dm-3. Repeatability of analysis expressed by relative standard deviation does not exceed the value of ± 8% and apparent recovery lay in acceptable range from 91 to 106 %. Stoichiometry between Eu(III) and Arsenazo III in media of relevant solution was 1:1. The absorbance of the solutions within the linear range of the proposed method maintained a constant value for 60 minutes. Described procedure can be utilized to determination of Eu(III) concentration in real samples, but it is necessary eliminate interfering ions. Cations like La(III), Sm(III), Th(IV), U(VI) and complexing agent EDTA cause significant error at the determination of Eu(III) in model solution. Presented spectrophotometric method could be applied for the determination of europium in the minerals and water samples, however after a suitable separation and preconcentration of target analyte.

Abstract

The aim of this study was to set parameters of repeated-batch cultivation of Ceriporiopsis subvermispora for laccase production and evaluate the efficiency of this type of cultivation for production of selected enzyme. The suitable conditions for repeated-batch cultivation were designed on the base of study of batch cultivation of white-rot fungus C. subvermispora. C. subvermispora was cultivated in media with different concentration of casein hydrolysate as nitrogen source and glucose as carbon source. A suitable concentration of casein hydrolysate to stimulate the laccase production was 1.5 and 2.5 g/L. Laccase production was started at certain critical concentration of glucose (5 g/L). In order to improve laccase production by repeated-batch cultivation of C. subvermispora, glucose was tested in concentration 10 g/L and casein hydrolysate in concentration 1.5 g/L. During a repeated-batch cultivation was measured increase laccase activities from 177.8 to 266 U/L. It was also observed, the cultivation time needed to reach maximum laccase production was shortened to 10 days.

Abstract

Total luminescence and synchronous scanning fluorescence spectroscopic techniques were investigated for differentiating brandies from mixed wine spirits. The studies were performed on 16 brandies from 3 different producers and 30 mixed wine spirits from 5 different producers. Differentiation between samples was accomplished by multivariate data analysis methods (principal component analysis, hierarchical cluster analysis, and linear discriminant analysis). Correct classification was obtained using emission spectra (400-650 nm) recorded at excitation wavelength 390 nm, excitation spectra (225-460 nm) obtained at emission wavelength 470 nm and synchronous fluorescence spectra (200-700 nm) collected at wavelength interval 80 nm. These results indicate that right-angle fluorescence spectroscopy offers a promising approach for the authentication of brandies as neither sample preparation nor special qualification of the personnel are required, and data acquisition and analysis are relatively simple when compared to front-face technique.

Abstract

Synthesis of methyl 4H-furo[3,2-b]pyrrole-5-carboxylate is taken place in two step synthesis. Vilsmeier-Haack reaction of 4H-furo[3,2-b]pyrrole-5-carboxylate 1 led to methyl 2-formyl-4H-furo[3,2- b]pyrrole-5-carboxylate 4, which served as starting compound for synthesis of furo[3,2-b]pyrrole-2- aldoxime 5 and methyl 2-[(4-oxo-2-thioxo-1,3-thiazolidin-5-ylidene)methyl]-4H-furo[3,2-b]pyrrole-5- carboxylate 7. The hydrazinolysis of 1 was prepared by carbohydrazide 2, which subsequently reacted with aldehydes to form of derivatives 3. Pyrazole derivatives 11 were prepared by the reaction of azlactone 9 with derivatives 10. Reactions were carried out under microwave irradiation or at classical heating.

Abstract

The synthesis and characterization of eleven new Cu(II) and Co(II) complexes is reported. The complexes were characterized by elemental analyses, infrared and electronic spectra. Copper(II) with 3- methylthiophene-2-carboxylic acid (HMTK) forms a dinuclear complex of the acetate type [Cu2(MTK)4(H2O)2]. By reaction of this complex with 2-metylfuro[3,2-c]pyridine (MeFP), not only acetate type complexes [Cu2(MTK)4L2] (L= FP, MeFP) were obtained, but also monomeric complex [Cu(MTK)2(FP)2]. In the cases of [1]benzofuro[3,2-c]pyridine (BFP) and 2-(3-trifluoromethylphenyl) furo[3,2-c]pyridine (CF3FP) only monomeric complexes [Cu(MTK)2L2] (L = BFP, CF3FP) were obtained. It is possible to observe, that with increasing amount of the ligand, the yield of monomeric complexes increases too. In monomeric complexes, the carboxylic group of anionic MTK binds to atom Cu(II) by asymmetrically chelating O,O-coordination. The crystal structure of the complex [Cu(MTK)2(MeFP)2] was determined by X-ray single crystal structure analysis. The copper(II) atom lies in the crystallographic centre of symmetry in an distorted tetragonal-bipyramidal arrangement. The structure of this complex confirms an asymmetric chelate coordination of the carboxylic group. HMTK and Cobalt(II) form coordination compound [Co(H2O)6](MTK)2 with assumed ionic mode of coordination of anionic MTK. With furopyridines monomeric complexes [Co(MTK)2L2] (L= FP, MeFP, BFP, CF3FP) with distorted octahedral coordination polyhedron around Co(II), were formed.

Abstract

Gradual increasing of glycerol concentration up to 10% using sheep ruminal fluid as an inoculum for in vitro cultivation was accompanied by significant changes in bacterial population as documented by DGGE analysis. The resulting bacterial consortium was composed of three dominant bacteria with Actinomyces related bacterium to be predominant. Upon cultivation on media with glycerol as a sole carbon source a single bacterium was cultivated from this consortium. Isolate G10 was found to be anaerobic, Gram-positive rod-shaped bacterium. Phylogenetic analysis based on 16S rRNA gene sequences showed that G10 isolate is related to the Actinomyces ruminicola species (97.7% of similarity). The role of rumen actinobacteria is largely unknown and their participation in glycerol utilization (tolerance) has not been described yet. The G10 bacterium and related consortium could be possibly used to improve glycerol tolerance and uptake by ruminants

Abstract

Concentration of available zinc from soils is the primary concern in assessment of its toxicity or essentiality for plants. This study evaluates the changes in chemical extractable Zn from three Slovak typical soils with simultaneous extractions as tools of zinc bioavailability. We found out that extractability of binding zinc decreased in order Na2EDTA, Mehlich 3, Mehlich 2, NH4NO3 and CaCl2 for all soil samples. Using flow-through stripping chronopotentiometry (SCP) and atomic absorption spectrometry (GFAAS) we found out that maximum of soil zinc was removed by organic ligands. Lability of Zn determined by isotopic dilution method using 65Zn and γ-spectrometry showed the significant decrease of isotopic exchangeable zinc fraction (E-value) with decrease of soil reaction. Obtained E-values of uppermost soil horizons showed the zinc lability ranged from 20 to 39%. Our research confirmed the effect of soil reaction, composition and physico-chemical characteristics to Zn lability. For further assessment of zinc bioavailability is needed to find the correlation and effects of structural changes and aging in studied soils

Abstract

The group selective molecularly imprinted polymers (MIPs) for coumarins, including umbelliferone, herniarin, 4-methylumbelliferone, scoparone were developed. Using umbelliferone as the template molecule, methacrylic acid as functional monomer, ethylene glycol dimethacrylate as linking agent, chloroform as porogen and bulk polymerization as synthetic method, the MIPs were synthesized and characterized with rebinding experiments. The characteristics of MIPs were evaluated by chromatographic method and frontal analysis, and demonstrating good selectivity and high binding capacity (269 μg of umbelliferone per 100 mg of polymer). The group selective MIP was used as sorbent for the SPE pretreatment of coumarins from propolis extracts prior to HPLC analysis. Analysis of the samples showed good recoveries (>70 %). The limits of quantitation (LOQs) for studied compounds were 0.3-10 ng.mL-1 (determined for fluorescence detection).

Abstract

Eleutherococcus senticosus is known as adaptogen with benefits in general health promotion. The aim of this study was to investigate the effect of major extraction parameters on extraction yield of antioxidants measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity. Secondly, content of total polyphenols was evaluated. Optimal conditions of the extraction were processed by response surface methodology. The independent variables of extraction were proposed as temperature, solid-liquid ratio and solvent composition. For the optimal antioxidant extraction, E. senticosus is suitable to extract by 23 % (v/v) aqueous ethanol at 70 °C in ratio 53 mL of extraction solvent per g of plant material. The optimal conditions calculated for the extraction of total polyphenols were very similar (70 °C, 22 % (v/v) aqueous ethanol) expect solid-liquid ratio which indicates need of increasing of solid-liquid ratio to 91 mL of extraction solvent per g of plant material