Structural Characterization of Mesoporous Silica Nanofibers Synthesized Within Porous Alumina Membranes

Mesoporous silica nanofibers were synthesized within the pores of the anodic aluminum oxide template using a simple sol–gel method. Transmission electron microscopy investigation indicated that the concentration of the structure-directing agent (EO20PO70EO20) had a significant impact on the mesostructure of mesoporous silica nanofibers. Samples with alignment of nanochannels along the axis of mesoporous silica nanofibers could be formed under the P123 concentration of 0.15 mg/mL. When the P123 concentration increased to 0.3 mg/mL, samples with a circular lamellar mesostructure could be obtained. The mechanism for the effect of the P123 concentration on the mesostructure of mesoporous silica nanofibres was proposed and discussed

Cloning of a novel gene from Penicillium oxalicum I1 which in Escherichia coli enhances the secretion of acetic acid

Description of the subject. Organic acids play an important role in the conversion of insoluble ions into soluble ones in soil. Heterologous overexpression of a single gene in a cell is the optimal strategy for increasing the secretion of organic acids solubilizing phosphate. Objectives. In this study, we constructed a primary cDNA library of Penicillium oxalicum I1, and screened clones that can solubilize P in tricalcium phosphate (TCP) medium. We aimed to obtain the gene expressed in Escherichia coli, which can enhance organic acid secretion. Method. A primary cDNA library of Penicillium oxalicum I1 was constructed using the switching mechanism at the 5’-end of RNA transcription. The organic acid secretion ability of E. coli DH5α™ with overexpressed P. oxalicum I1gene was tested in TCP medium where glucose is the sole carbon source. Afterwards, pyruvic acid, citric acid, α-ketoglutaric acid, succinic acid, fumaric acid, and malic acid were used as sole carbon source substitutes for glucose in the TCP medium to test the organic acid secretion ability of the transformed E. coli DH5α™. Results. A total of 106 clones showed halos in TCP medium, among which clone I-2 displayed clear halo. The full-length cDNA of clone I-2 was 1,151 bp, with a complete open reading frame of 702 bp, which encoded a hypothetical protein of 233 amino acids. The cDNA sequence showed 68% identity and 73% query cover with other fungal gene sequences of which the function remains unknown. Escherichia coli containing the cloned gene secreted up to 567 mg.l-1 acetic acid within 48 h. The use of glucose, pyruvic acid, α-ketoglutaric acid, and malic acid improved the acetic acid secretion of the E. coli DH5α™ clone I-2. By contrast, the use of citric acid, succinic acid, and fumaric acid did not improve the acetic acid secretion of clone I-2 compared to a control E. coli DH5α™ strain bearing only the cloning vector without any insert. Conclusions. We obtained a novel gene from Penicillium oxalicum I1 whose overexpression in E. coli DH5α™ increased the secretion of acetic acid. This observation should help to understand what is the function of the gene isolated from P. oxalicum as well as that of its homologs found in several other species of the Penicillium genus

Effect of Spherical Nanoparticles on the Motion of Macromolecular Chains and Segments of Isotactic Polypropylene. I. Dynamic Mechanical and Thermal Properties

The role of spherical nano-CaCO3 particles treated with 2 wt\% and 6 wt\% stearic acid (SA), respectively, on the motion of macromolecular chains and segments of isotactic polypropylene (iPP) was studied through the dynamic mechanical analysis and nonisothermal crystallization. Higher nucleation activity of the particles and more nucleating sites were achieved in the 6 wt\% SA treated particle nanocomposites with respect to the 2 wt\% SA counterpart. The increased nucleation efficiency caused high inhomogeneity and thus large mobility of the amorphous phase of iPP, which favored a low glass transition temperature (Tg) in the nanocomposites. However, the spherical nanoparicles also spatially restrained the motion of macromolecular chains and segments, and the better the nanoparticles dispersed, the stronger the restriction was. Thus the glass transition temperature (Tg) of the nanocomposites decreased with increasing filler loading but recovered at a certain particle concentration. At this filler content, the maximal -transition temperature (T) and the main melting peak temperature (Tm1) as well as the lowest degree of crystallinity (XPP) also occurred. This critical filler loading appeared at lower value (20 wt\%) in 6 wt\% SA treated nano-CaCO3 composites with respect to 2 wt\% SA counterpart (25\%) due to the better dispersion of particles in the former. It was concluded that the mobility of the macromolecular chains and segments of iPP was dominated by the competition of the spatial confinement and nucleation effect of nano-CaCO3 particles in the matrix

Dynamic Rheological Behavior of Isotactic Polypropylene Filled With Nano-Calcium Carbonate Modified by Stearic Acid Coating

2 wt\% and 6 wt\% stearic acid (SA)-coated calcium carbonate (CaCO3) nanoparticles were compounded with isotactic polypropylene (iPP). Small-amplitude oscillatory shear tests were used to study the linear viscoelastic properties of the nanocomposite melts. The filler loading at which the composites exhibited the terminal modulus plateau was found to be much lower in the 6 wt\% SA-coated particle composites than in the 2 wt\% counterpart, and at the same filler content, apparently higher dynamic moduli and complex viscosities at low frequencies were shown in the former. The characteristics of pseudo-solid-like behavior almost disappeared in the 2 wt\% SA-coated particle composites as the gap distance increased but were still observed in the 6 wt\% counterpart. The results indicate that the dispersion of nanoparticles played a critical role in the motion of the macromolecular chains. At the same filler loading, the mobility of the iPP melts was more severely restricted by properly coated and well-dispersed nanoparticles than by aggregates due to insufficient coating

Large Eddy Simulation of the fuel transport and mixing process in a scramjet combustor with rearwall-expansion cavity

Large Eddy Simulation (LES) was employed to investigate the fuel/oxidizer mixing process in an ethylene fueled scramjet combustor with a rearwall-expansion cavity. The numerical solver was first validated for an experimental flow, the DLR strut-based scramjet combustor case. Shock wave structures and wall-pressure distribution from the numerical simulations were compared with experimental data and the numerical results were shown in good agreement with the available experimental data. Effects of the injection location on the flow and mixing process were then studied. It was found that with a long injection distance upstream the cavity, the fuel is transported much further into the main flow and a smaller subsonic zone is formed inside the cavity. Conversely, with a short injection distance, the fuel is entrained more into the cavity and a larger subsonic zone is formed inside the cavity, which is favorable for ignition in the cavity. For the rearwall-expansion cavity, it is suggested that the optimized ignition location with a long upstream injection distance should be in the bottom wall in the middle part of the cavity, while the optimized ignition location with a short upstream injection distance should be in the bottom wall in the front side of the cavity. By employing a cavity direct injection on the rear wall, the fuel mass fraction inside the cavity and the local turbulent intensity will both be increased due to this fueling, and it will also enhance the mixing process which will also lead to increased mixing efficiency. For the rearwall-expansion cavity, the combined injection scheme is expected to be an optimized injection scheme

An alkaline and surfactant-tolerant lipase from Trichoderma lentiforme ACCC30425 with high application potential in the detergent industry

Abstract Alkaline lipases with adaptability to low temperatures and strong surfactant tolerance are favorable for application in the detergent industry. In the present study, a lipase-encoding gene, TllipA, was cloned from Trichoderma lentiforme ACCC30425 and expressed in Pichia pastoris GS115. The purified recombinant TlLipA was found to have optimal activities at 50 °C and pH 9.5 and retain stable over the pH range of 6.0–10.0 and 40 °C and below. When using esters of different lengths as substrates, TlLipA showed preference for the medium length p-nitrophenyl octanoate. In comparison to commercial lipases, TlLipA demonstrated higher tolerance to various surfactants (SDS, Tween 20, and Triton X100) and retained more activities after incubation with Triton X100 for up to 24 h. These favorable characteristics make TlLipA prospective as an additive in the detergent industry