Induction and catabolite repression of cellulase inPenicillium funiculosum

The regulation of endoglucanase synthesis in Penicillium funiculosum is investigated using a method based on the viscosity lowering effect on carboxy methyl cellulose (CMC) by endoglucanase. Cellobiose (1 mg/L) causes induction, whereas glucose (5 g/L) does not repress the enzyme formation. Lactose (5 g/L) has no effect on the synthesis of cellulase. Avicel and cellulose powder (CP) are the best inducers of cellulase and xylanase activity. Both endoglucanase and xylanase activity were induced by CMC, whereas xylan induced only xylanase activity. The effect of protease on induction of cellulase activity is discussed.     

Liquid chromatography-tandem mass spectrometry for the identification of L-tetrahydropalmatine metabolites in Penicillium janthinellum and rats

L-tetrahydropalmatine (L-THP) is an active alkaloid from Stephania ainiaca Diels. In order to compare the similarities and differences of microbial and mammalian metabolisms of L-THP, the microbial transformation by Penicillium janthinellum and metabolism in rats were investigated. Biotransformation of L-THP by Penicillium janthinellum AS 3.510 resulted in the formation of three metabolites. Their structures were identified as L-corydalmine, L-corypalmine and 9-O-desmethyl-L-THP, respectively, by comprehensive nuclear magnetic resonance and mass spectrometry (MS) analysis. Six metabolites (M1-M6) were detected from the in vivo study in rats and three of which (L-corydalmine, L-corypalmine and 9-O-desmethyl-L-THP) were identified as the same compounds as those obtained from microbial metabolism by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis and comparison with reference standards obtained from microbial metabolism. The structures of the additional three metabolites were tentatively deduced as 2-O-desmethyl-L-THP and two di-O-demethylated L-THP by LC-MS/MS analysis. Time courses of microbial and rat metabolisms of L-THP were also investigated.     

Effect of LED Blue Light on Penicillium digitatum and Penicillium italicum Strains

Studies on the antimicrobial properties of light have considerably increased due in part to the development of resistance to actual control methods. This study investigates the potential of light‐emitting diodes (LED) blue light for controlling Penicillium digitatum and Penicillium italicum. These fungi are the most devastating postharvest pathogens of citrus fruit and cause important losses due to contaminations and the development of resistant strains against fungicides. The effect of different periods and quantum fluxes, delaying light application on the growth and morphology of P. digitatum strains resistant and sensitive to fungicides, and P. italicum cultured at 20°C was examined. Results showed that blue light controls the growth of all strains and that its efficacy increases with the quantum flux. Spore germination was always avoided by exposing the cultures to high quantum flux (700 μmol m^?2 s^?1) for 18 h. Continuous light had an important impact on the fungus morphology and a fungicidal effect when applied at a lower quantum flux (120 μmol m^?2 s^?1) to a growing fungus. Sensitivity to light increased with mycelium age. Results show that blue light may be a tool for P. digitatum and P. italicum infection prevention during handling of citrus fruits.     

Effect of catalyst mass on CVD synthesis of carbon nanotubes

Method for obtaining carbon nanotubes by chemical vapor deposition on metal oxide catalysts produced by the reaction of transition metal nitrates with glycine was considered. The process of synthesis of carbon nanotubes was experimentally studied at various reaction durations, temperatures, and amounts of a catalyst. It was found that the ash content of the product and the content of impurities depend on the amount of a catalyst. A reactor design raising the output capacity of the process for synthesis of carbon nanotubes is suggested.     

Effect of temperature, moisture, and carbon supplementation on lipase production by solid-state fermentation of soy cake by Penicillium simplicissimum

The production of lipases by Penicillium simplicissimum using solid-state fermentation and soy cake as substrate was investigated. The effects of temperature, cake moisture, and carbon supplementation on lipase production were studied using a two-level experimental plan. Moisture, pH, and lipase activity were followed during fermentation. Statistical analysis of the results was performed to evaluate the effect of the studied variables on the maximum lipase activity. Incubation temperature was the variable that most affected enzyme activity, showing a negative effect. Moisture and carbon supplementation presented a positive effect on activity. It was possible to obtain lipase activity as high as 21 U/g of dry cake in the studied range of process variables.     

Effect of single-walled carbon nanotubes with imide cycles on the synthesis and properties of polycaproamide

The anionic polymerization of ε-caprolactam in the presence of single-walled carbon nanotubes with grafted acyllactam groups or polyimide macromolecules is performed. It is shown that the polymerization of ε-caprolactam slows down with an increase in the filler concentration. The introduction of 0.01 wt % nanotubes with polyimide fragments into polycaproamide leads to a 25% increase in the compressive modulus. In this case, the Izod impact strength is 10 kJ/m², that is, 150% higher than that for an unfilled polycaproamide or polycaproamide containing other types of nanotubes.     

Effect of catalyst confinement and pore size on Fischer-Tropsch synthesis over cobalt supported on carbon nanotubes

This paper studies the impact of structure of cobalt catalysts supported on carbon nanotubes(CNT) on the activity and product selectivity of Fischer-Tropsch synthesis(FTS) reaction.Three types of CNT with average pore sizes of 5,11,and 17 nm were used as the supports.The catalysts were prepared by selectively impregnating cobalt nanoparticles either inside or outside CNT.The TPR results indicated that the catalyst with Co particles inside CNT was easier to be reduced than those outside CNT,and the reducibility of cobalt oxide particles inside the CNT decreased with the cobalt oxide particle size increasing.The activity of the catalyst with Co inside CNT was higher than that of catalysts with Co particles outside CNT.Smaller CNT pore size also appears to enhance the catalyst reduction and FTS activity due to the little interaction between cobalt oxide with carbon and the enhanced electron shift on the non-planar carbon tube surface.     

Effect of ultrasound on a mixed oxide-based catalyst for synthesis of nanostructured carbon materials

The effect of ultrasonic activation on the performance of a mixed oxide-based (Ni/Mg) catalyst in the synthesis of multiwalled carbon nanotubes via chemical vapor deposition was studied. The molecular geometry of the solution of initial catalyst components (feed solution) was calculated and simulated according to a molecular mechanics method. Activation of the catalyst performed for 10 s during its preparation stage resulted in a considerable increase (of about 40 %) in the specific yield of nanotubes due to enhanced catalytic activity. Moreover, the kinetics of nanotube synthesis over the activated catalyst was studied, and the morphology of the obtained nanoproduct was investigated. Finally, the possibility of employing the present method for catalyst activation in experimental–industrial production of nanotubes was evaluated.     

The dependence of asymmetric induction on solvent polarity and temperature in peptide synthesis

When a racemic 2,4-dialkyl-5(4$\text{H}$)-oxazolone reacts with an L-amino acid ester, the DL epimer is formed in excess in apolar solvents and the LL epimer is formed in excess in polar solvents, the proportion of LL isomer increasing with decreasing temperature.     

Effect of the AACVD based synthesis atmosphere on the structural properties of multi-walled carbon nanotubes

The synthesis of multi-walled carbon nanotubes (MWCNT_S) has been the focus of considerable research effort for more than twenty-five years and it continues to receive increasing attention because of its importance to produce carbon nanotubes with suitable parameters for future applications. To the best of our knowledge this study presents for the first time the complex studies concerning the effect of aerosol-assisted chemical vapour deposition (AACVD) process conditions (including temperature (750–1200 °C) and the composition of the carrier gas (N₂, Ar, He, 5% H₂-95% Ar, 3% H₂O-97% Ar)) on the conversion of the carbon source and on the properties of the carbon nanotubes. In addition, it was also found that oxidative or reductive atmosphere applied during the AACVD process have a great impact on the quality and the degree of toluene conversion into the carbon solids obtained during the synthesis. X-ray Diffraction (XRD), Specific Surface Area and Porosity analysis (BET), Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM-EDS), Transmission Electron Microscopy (TEM), Raman spectroscopy and Thermo-gravimetric Analysis (TG) were used to characterize the carbon nanotubes.     

介孔炭的孔结构对其负载的Ru基氨合成催化剂性能的影响

采用模板法合成了介孔炭(MC),研究了其孔结构对其负载的Ru基氨合成催化剂Ba-Ru-K/MC性能的影响,采用N₂吸附脱附、扫描电镜和透射电镜等手段对介孔炭的孔结构进行了表征.研究发现,介孔炭载体的孔结构取决于模板剂的用量,当SiO₂/C质量比为1.0时,所制介孔炭比表面积最大.介孔炭负载的Ba-Ru-K催化剂活性与其介孔比表面积相关.在425℃,10MPa和10000h^-1条件下,合成氨的反应速率为139mmol/(g_cat·h).     

Effect of time on the metal-support (Fe-MgO) interaction in CVD synthesis of single-walled carbon nanotubes

A study on the effect of the metal-support interaction by employing iron particles supported on magnesium oxide (MgO) nanopowder in an alcohol-CVD process for single-walled carbon nanotubes growth is presented. Upon the prolongation of the process time, three main observations were detected: (i) decrease of the mean nanotubes diameter, (ii) reduction of the diameter distribution by the factor of two, (iii) increase of relative purity of the samples.     

Selective matching of catalyst element and carbon source in single-walled carbon nanotube synthesis on silicon substrates

We have studied the compatibility of various catalysts for ethylene and ethanol chemical vapor deposition (CVD) syntheses of single-walled carbon nanotubes (SWNTs) on Si substrates. A strong selectivity between the catalyst elemental species and carbon source was found; SWNT yield for Fe (Co) catalysts was much higher for ethylene (ethanol) CVD than for ethanol (ethylene) CVD. This strong and completely opposite selectivity implies significantly different SWNT growth mechanisms for ethanol and ethylene CVD on Si substrates.     

Effect of the matrix composition on the activity of metal oxide catalysts in CVD synthesis of carbon nanotubes

Citrate-nitrate method was used to synthesize (Fe,Co)/MgO-Al₂O₃, (Fe,Mo)/MgO-Al₂O₃, and (CoMo)/MgO-Al₂O₃ catalysts for production of carbon nanotubes. Multi-walled nanotubes were formed on these catalysts by catalytic pyrolysis of a propane-butane mixture.     

The mechanism of sugar-dependent repression of synthesis of catabolic enzymes in Escherichia coli.

Previous studies have indicated that the Escherichia coli adenylate cyclase (AC) activity is controlled by an interaction with the phosphoenolpyruvate (PEP): sugar phosphotransferase system (PTS). A model for the regulation of AC involving the phosphorylation state of the PTS is described. Kinectic studies support the concept that the velocity of AC is determined by the opposing contributions of PEP-dependent phosphorylation (V1) and sugar-dependent dephosphorylation (V2) of the PTS proteins according to the expression percent VAC=100/[1 + (Max V2/Max V1)]. Physiological parameters influencing the rate of the PTS are discussed in the framework of their effects on cAMP metabolism. Factors that increase cellular concentration of PEP (and stimulate V1) appear to enhance AC activity while increases in extracellular sugar concentration (which stimulate V2) or internal levels of pyruvate (which inhibit V1) inhibit the activity of this enzyme.     

Effects of process parameters on ultrafine SiC synthesis using induction plasmas

A study is reported of the formation of ultrafine SiC powder through the reaction of elemental silicon and CH₄ in an induction plasma. The reaction route used involved in the first place the vaporization of a fine elemental silicon powder axially injected into the center of the discharge followed by the carburization reaction through the coinjection of CH₄. The powder obtained was composed of a mixture of α- and β-SiC with varying amounts of free carbon and free silicon. The particle size distribution was typically in the range of 40–60 nm with a corresponding specific surface area of 30–50 m²/g. A parametric study showed that the quality of the powder obtained varied with the plasma plate power and the position of the injection probe. The plasma gas composition employed was found to influence the proportions of α- and β-SiC in the synthesized SiC powder. With an Ar/N₂ mixture as the plasma gas, the ratio of the α to β phases was less than 1.0, whereas the ratio was greater than 1.5 when using a mixture of Ar/H₂ as plasma gas. The Si powder feed rate and the input C/Si molar ratio in the injected reactants significantly affected both the formation of the SiC and the free Si and free C content in the synthesized powder. Lining the cylindrical reactor wall with graphite resulted in improved conversion of Si to SiC. The weight fraction of the powder collected at different sections of the reactor system varied with the reactor operating conditions. The experimental results support the view that the formation mechanism for ultrafine SiC is dominated by the reaction of Si vapor with the thermal decomposition products of CH₄.     

The synthesis and study of silicon-containing nanodispersed carbon

Samples of silicon dioxide-modified nanospherical carbon were synthesized by thermooxidative pyrolysis of highly aromatized liquid hydrocarbons with a varied content of organosilicon polymer (polyorganosiloxane). The physicochemical properties of the product synthesized were studied.