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Production of (R)-styrene oxide by recombinant whole-cell biocatalyst in aqueous and biphasic system

Abstract

The enantioselective resolution of racemic styrene oxide (rac-SO) to (R)-SO by whole cells of a recombinant Escherichia coli expressing epoxide hydrolase (EH) activity in aqueous and biphasic system were studied. Some parameters that may alter this bio-resolution, such as the concentration of recombinant cell, substrate and product were evaluated. The effect of the addition of different additives on the course of rac-SO biotransformation was also investigated. The results showed that the yield and the enantiomeric excess (ee) of (R)-SO were dependent on these variables. When the kinetic resolution was conducted with 350 mM of rac-SO, enantiopure (R)-SO with high (≥99%) ee was obtained with a yield of 38.2% yield at 12.2 h in the presence of 10% (v/v) Tween 80. An isooctane/aqueous system was developed to overcome the adverse factors in the aqueous phase, resulting in an improvement of yield from 38.2% to 42.9%. The results will provide a useful guidance for further application of this enzyme in the biocatalytic production of chiral synthons.

Open access
Removal of Pb(II) ions from aqueous solution using complexation-ultrafiltration

Abstract

Ligand-modified micellar-enhanced ultrafiltration (LM-MEUF) is a membrane technique based on a separation process which can be used for removal of target metals from an aqueous solution. This method involves adding both a metal complexing ligand and surfactant molecule to the aqueous solution under conditions where most of the molecules are present as micelles. This ligand can be attached to the surface of micelles by solubilization and forms the ligand complexes with the metal ion. The aqueous solution is then treated through a membrane which has to be smaller pore sizes than those of the complexes. Hence, permeate water is then purified from the heavy metals. In this study, divalent lead is the target ion in a solution. Filtration experiments were performed with ultrafiltration membrane system, equipped with a regenerated cellulose membrane with a 5000 Daltons cutoff. The pressure was fixed at 4.0 bar with a permeate flow rate of 500 mL min−1. Complexes of Pb2+ ions with three ligands were investigated in micellar medium of different surfactants at different pH values to determine the ligands which could provide separation. Different parameters affecting the percentage rejection of the Pb2+, such as pH and surfactant concentration were also discussed. Results have shown that the maximum percentage of the Pb2+ ions rejection were obtained using sodium dodecyl sulfate (SDS) as a surfactant and dithizone (DZ) as the lead-specific ligand. A waste stream sample from a battery plant was subjected to LM-MEUF process in the optimum conditions determined in this study and it was shown that Pb2+ ions in a waste stream could be removed by LM-MEUF effectively.

Open access
Statistical optimization of the synthesis of plant-derived fatty acid esters of TMP over homogeneous organometallic tin catalyst

Abstract

A class of very important industrial-grade biolubricants was synthesized from plant-derived fatty acids (oleic and isostearic acid) by direct esterification of trimethylolpropane according to novel effective and high selective method using Sn bis(2-ethylhexanoate) as catalyst. Model transesterification reactions were performed with oleic and isostearic acids to optimize the reaction conditions to obtain maximum content of TMP triesters. Used specific homogeneous Sn catalyst allows to obtain TMP esters with very high content of triesters, above of 94 wt% without deep vacuum purifying distillation. Both TMP esters were evaluated for their physicochemical and tribological properties using ASTM standards. Both TMP esters exhibited high viscosity indexes and excellent low temperature properties.

Open access
Synthesis, characterization of Hollandite Ag2Mn8O16 on TiO2 nanotubes and their photocatalytic properties for Rhodamine B degradation

Abstract

In this research Ag2Mn8O16 nanocrystals/TiO2 nanotubes, photoelectrodes were successfully prepared through anodization and annihilation steps, followed by electrodeposition of MnO2 and Ag in a three electrodes cell. The obtained photoelectrodes were dried, then annealed for crystallization, the morphology and structure of the fabricated electrodes were characterized via scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The light absorption and harvesting properties were investigated through UV–visible diffuse reflectance spectrum (DRS), photocatalytic performances were evaluated by degradation of 50 mL of Rhodamine B (5 mg L−1) under Xenon light irradiation for 2 h. Results illustrated that the fabricated photoelectrodes show remarkable photo-degradation properties of organic pollutants in aqueous mediums.

Open access
Synthesis of a novel environmental friendly plasticizer based on tung oil fatty acid for poly (vinyl chloride) blends

Abstract

A novel environmental friendly plasticizer (TPE) derived from tung oil fatty acid with long fatty acid chain and high degree of branching was synthesized. Chemical structure of the obtained TPE was characterized with Fourier transform infrared spectroscopy (FT-IR) and 1H NMR. TPE was used to prepare plasticized PVC blends as main plasticizer. Thermal stability, mechanical properties and migration resistance of poly (vinyl chloride) plasticized with TPE were investigated. The results showed that torque data of plasticized PVC blends reached 12.4 N·m when the mass of the TPE was 50 wt.%. TPE improved the thermal stability of PVC blends obviously than dioctyl phthalate (DOP). The leaching tests showed that PVC plasticized with TPE were with higher migration resistance than that of DOP. The excellent thermal stability and high migration resistance of PVC blends showed high application value for TPE.

Open access
Use of carbon and aluminosilicate nanofillers in XNBR composites designed for protective materials against oils

Abstract

The objective of the work was to investigate the possibility of application of carbon and bentonite nanoparticles in carboxylated acrylonitrile-butadiene rubber (XNBR) and the related effects of the nanofillers on the structure, as well as mechanical and barrier properties, of the resulting composites. The composites were designed for use in protective clothing and gloves. XNBR compounds were modified with 2 phr of graphene flakes, graphene oxide, or modified bentonite, and crosslinked with sulfur-accelerator system. Rubber compounds were prepared using a conventional method with a laboratory rolling mill. The composites were studied in terms of structure (WAXS), surface morphology (AFM), the presence of functional groups (ATR-FTIR) barrier properties against chemical substances (mineral oil) and swelling properties, as well as mechanical properties (abrasion resistance and tensile strength). The composites were characterized by very high resistance to oil permeation (breakthrough time >480 min). The type of nanofiller added to the XNBR blend in the amount of 2 phr did not significantly affect mechanical parameters.

Open access
Biodegradable polylactide and thermoplastic starch blends as drug release device – mass transfer study

Abstract

Four different compositions of polylactide/thermoplastic starch blends (PLA/TPS blends) for application as drug carriers were examined. Initially, using cyanocobalamin (1.355 kDa) as a model compound, the blend with the highest starch content (wt. 60%) was selected for further research of mass transfer phenomenon. In this case, different concentrations of acetaminophen (0.151 kDa), doxorubicin hydrochloride (0.580 kDa) and cyanocobalamin (1.355 kDa) were used for determination of particular releasing profiles. Besides from the comparative analysis of obtained results, the values of the overall mass transfer coefficient (K) were calculated for each of tested drug molecules. Depending on the size and properties of used compound, determined values of the coefficient range from 10−11 to 10−13 m/s. Based on these outcomes, it could be stated that PLA/TPS blend selected in preliminary research, seems to be preferred material for fabrication of long-term drug delivery systems, which could be successfully applied for example in anti-cancer therapy.

Open access
Composite coatings with nickel matrix and graphene as dispersed phase

Abstract

The paper presents the results of the studies of nickel-graphene composite coatings deposited by the electrochemical reduction method. A bath with low concentration of nickel ions, graphene as dispersed particles and organic compounds were used for deposition of the composite coatings nickel-graphene. The results of investigations of coatings deposited from the electrolyte containing 0.33, 0.5 and 1 g/dm3 graphene and two surface-active compounds were shown. The particles content in the coatings, the surface morphology, the cross-sectional structures of the coated samples, thickness and internal stresses were measured. Voltammetric method was used for examination of the corrosion resistance of samples of composite coatings in 0.5 M NaCl solution. The obtained results suggest that the content of incorporated graphene particles increases with an increasing amount of graphene in plating bath. The applications of organic addition agents was advantageous because it caused compressive stresses in the coatings. All of the nickel-graphene composite coatings had better corrosion resistance than the nickel coatings.

Open access
Effects of processing parameters on the properties of amphiphilic block copolymer micelles prepared by supercritical carbon dioxide evaporation method

Abstract

The operation parameters for the supercritical carbon dioxide (ScCO2) evaporation method greatly affect the properties of the prepared drug-loaded micelles. In this study, the effects of those key parameters on the drug-loading content (LC) and drug entrapment efficiency (EE) are discussed. It is observed that EE and LC of the micelles are slightly increased with the enhancing temperature and the copolymer molecular ratio of hydrophilic/hydrophobic segment, while decreased with the enhancing ScCO2 evaporation rate. The pressure and volume ratio of ScCO2 to H2O are observed the optimum condition. In addition, the verification experiment is carried out under the obtained optimizing parameters. The prepared micelles exhibit relatively regular spherical shape and narrow size distribution with the EE and LC value of 70.7% and 14.1%, respectively.

Open access
Electrooxidation of phenol on carbon fibre-based anodes through continuous electrolysis of synthetic wastewater

Abstract

This work reports on the process of phenol electrooxidation, which is carried-out through continuous electrolysis of synthetic, sodium sulphate-based wastewater. Phenol electrodegradation is examined by means of a laboratory size (ca. 700 cm3 of working volume), poly (methyl methacrylate)-made electrolyser unit for various, carbon fibre and graphite-based anode configurations, and stainless steel cathodes, two different current-densities and concentrations of phenol in synthetically prepared wastewater solution. Proper monitoring of phenol degradation (including quantitative identification of reaction products and calculation of specific energy consumption) in wastewater is performed by means of instrumental, combined HPLC and MS technique in function of electrolysis time.

Open access