Hybrid sonochemic urea-nitrate combustion preparation of CuO/ZnO/Al2O3 nanocatalyst used in fuel cell-grade hydrogen production from methanol: Effect of sonication and fuel/nitrate ratio

Fuel cell-grade hydrogen production has been studied via steam reforming of methanol (SRM) over a series of CuO/ZnO/Al₂O₃ nanocatalysts fabricated by the combustion method. The effect of sonication and urea/nitrate ratio on the characteristics and catalytic properties of the prepared catalysts has been investigated. The synthesized catalysts were characterized by x-ray diffraction (XRD), field emission scanning electron microscope (FESEM), Particle Size Distribution (PSD), energy dispersive x-ray (EDX), Brunauer-Emmett-Teller (BET) and FTIR analyses XRD patterns showed positive influence of urea/nitrate ratio on CuO and ZnO crystallite sizes. The ultrasonic mixing of primary gel compared with conventional mixing led to lower crystallite size. FESEM images showed that the sample mixed by sonication with a urea/nitrate ratio of 1 had more homogeneous morphology with narrow particle size distribution. EDX results proved the presence of all metals on the surface of the nanocatalysts and better consistence between the gel and surface composition of elements in samples prepared by sonication. Catalytic performance showed that sonication during the mixing of primary gel dramatically increased the methanol conversion. It was also proved that increasing the amount of urea led to lower catalytic activity. The ultrasound-treated nanocatalyst with urea/nitrate?=?1 was the best sample in terms of activity and selectivity. It was stable in the SRM for 1200?min without considerable change in methanol conversion and product selectivity.     

Using state-space models for solving elastodynamic problems discretized by the MLPG method

One of the popular methods for solving ordinary differential equations is the state-space approach. In this paper, the use of the state-space method to analyze elastodynamic problems, discretized by the MLPG method, is proposed. Two methods commonly used in solving such problems, namely, the central difference method and the Newmark method, are compared with the proposed method. To examine the accuracy and the computational time of the new method, an example is studied. The results of the implementation of these methods are compared with a finite element solution. The results show that the state-space method saves substantial computational time for a given accuracy.     

Stable repeated-batch production of recombinant dye-decolorizing peroxidase (rDyP) from Aspergillus oryzae

Recombinant Aspergillus oryzae expressing a dye-decolorizing peroxidase gene (dyp) was cultivated for repeated-batch production of recombinant dye-decolorizing peroxidase (rDyP) using maltose as a carbon source. High-level rDyP activity in limitation of carbon and nitrogen sources was maintained stably for 26 cycles of repeated 1-d batches of A. oryzae pellets without any additional pH control. Cultures maintained at 4 degrees C for 20 d resumed rDyP production following a single day of incubation. One liter filtrated crude rDyP containing 4600 U rDyP decolorized 5.07 g RBBR at the apparent decolorization rate of 17.7 mg l(-1) min(-1).     

Production of dye-decolorizing peroxidase (rDyP) from complex substrates by repeated-batch and fed-batch cultures of recombinant Aspergillus oryzae

We examined production levels of dye-decolorizing peroxidase (rDyP) by recombinant Aspergillus oryzae using wheat bran and rice bran powders in repeated-batch and fed-batch cultures. Similar average rDyP productivities were observed in repeated-batch cultures using wheat bran powder and rice bran powder. Average rDyP productivities in fed-batch cultures were slightly lower than those in repeated-batch cultures. The rDyP production was affected by the addition of K(2)HPO(4) in the repeated-batch and fed-batch cultures using wheat bran powder. All average rDyP productivities in this study were significantly higher than those for any other peroxidases previously reported.     

Influence of surfactants on an extracellular lipase fromPhythium ultimum

The online version of the original article can be found at     

Removal of reactive red-120 and 4-(2-pyridylazo) resorcinol from aqueous samples by Fe3O4 magnetic nanoparticles using ionic liquid as modifier

The nanoparticles of Fe₃O₄ as well as the binary nanoparticles of ionic liquid and Fe₃O₄ (IL-Fe₃O₄) were synthesized for removal of reactive red 120 (RR-120) and 4-(2-pyridylazo) resorcinol (PAR) as model azo dyes from aqueous solutions. The mean size and the surface morphology of the nanoparticles were characterized by TEM, DLS, XRD, FTIR and TGA techniques. Adsorption of RR-120 and PAR was studied in a batch reactor at different experimental conditions such as nanoparticle dosage, dye concentration, pH of the solution, ionic strength, and contact time. Experimental results indicated that the IL-Fe₃O₄ nanoparticles had removed more than 98% of both dyes under the optimum operational conditions of a dosage of 60 mg, a pH of 2.5, and a contact time of 2 min when initial dyes concentrations of 10-200 mg L⁻¹ were used. The maximum adsorption capacity of IL-Fe₃O₄ was 166.67 and 49.26 mg g⁻¹ for RR-120 and PAR, respectively. The isotherm experiments revealed that the Langmuir model attained better fits to the equilibrium data than the Freundlich model. The Langmuir adsorption constants were 5.99 and 3.62 L mg⁻¹ for adsorptions of RR-120 and PAR, respectively. Both adsorption processes were endothermic and dyes could be desorbed from IL-Fe₃O₄ by using a mixed NaCl-acetone solution and adsorbent was reusable.     

Influence of surfactants on an extracellular lipase fromPythium ultimum

The activity of an extracellular lipase from the fungusPythium ultimum was studied as a function of emulsion properties, and the amount and type of surfactants used in preparing the emulsions. The highest emulsified globule surface area as a function of surfactant concentration and emulsion stability were in the order taurocholic acid >Triton X-100>3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS). Lipase activity was dependent on both the type and the concentration of surfactant, with taurocholic acid and CHAPS giving tenfold stimulation over the control at 0.1 and 0.8 mM, respectively. The evidence suggests that the influence of surfactant is related more to interaction with the enzyme at the oil-water interface than to providing greater interfacial surface area.     

Invert emulsion as a medium for fungal lipase activity

An extracellular lipase from the fungusPythium ultimum was active in an invert [water-in-oil] emulsion consisting of 4% water emulsified into edible oils with taurocholic acid as the surfactant. The pH range for optimum lipolytic activity was 7.5–8.5, and the optimum temperature for activity was 45°C. Specific activity of the purified lipase was 919.5 μmol/min/mg protein in the invert emulsion. Water content of the invert emulsion influenced activity of the lipase differently, depending on the substrate. The rate of olive oil hydrolysis with thePythium lipase decreased with time, possibly due to inactivation of the enzyme and inhibition by free fatty acid products of the reaction. Total hydrolysis of olive oil by thePythium lipase was compared with that by lipases fromCandida rugosa andRhizopus arrhizus in the invert emulsion. Hydrolysis essentially ceased within 24 h or less for the lipases from each source. However, the addition of aqueous solution at 8 h from the beginning of incubation stimulated hydrolysis byC. rugosa andR. arrhizus lipases by 1.8-fold and 2.5-fold, respectively, but not by theP. ultimum lipase, over corresponding controls after 48 h.     

Purification and properties of an extracellular lipase fromPythium ultimum

An extracellular triacylglycerol lipase (EC 3.1.1.3) fromPythium ultimum strain No. 144 was purified by ammonium sulfate precipitation, and by diethylaminoethyl Sepharose CL-6B and Sephacryl S−200 chromatography. The purified enzyme preparation showed a prominent polypeptide band in polyacrylamide gel electrophoresis, associated with esterase activity according to activity staining. Molecular weight of the protein was estimated at 270 kD using gel filtration on Sephacryl S−200, and 68 kD by sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicating that the enzyme may be a tetramer. The optimum pH and temperature for activity of the enzyme were 8.0 and 30°C, respectively. Activity was reduced by Co²⁺, Fe²⁺, Sn²⁺ and Mn²⁺ and stimulated by Ca²⁺, Mg²⁺, Na⁺, K⁺ and surfactants such as taurocholic acid, Triton X−100,n-octyl glucoside,n-dodecyl-β-D-maltoside, 3-[(3-cholamidopropyl) dimethylammonio]-1-propanesulfonate(CHAPS), and 3-[-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulfonate. The apparent maximum specific activity was 42 μmole/min/mg in the absence of CHAPS and 77 μmole/min/mg in its presence. The reaction rate was progressively higher with increasing number of double bonds in the substrate, and the enzyme showed a preference for triacylglycerols containing fatty acids having thecis double bond configuration. AAES publication No. 6-933419.