Screening of culture condition for xylanase production by filamentous fungi

The objective of this research was to investigate xylanase production by filamentous fungi (Trichoderma viride) to determine the best cultivation conditions in the process, aiming toward optimization of enzyme production. The best temperature, as well as the best carbon source, for biomass production was determined through an automated turbidimetric method (Bioscreen-C). The enzyme activity of this fungus was separately evaluated in two solid substrates (wheat and soybean bran) and in Vogel medium, pure and by adding other carbon sources. Temperature effects, cultivation time, and spore concentrations were also tested. The best temperature and carbon source for enzyme and biomass production was 25 C and sorbitol, respectively. Maximum xylanase activity was achieved when the fungus was cultivated in wheat bran along with sorbitol (1%, w/v), using a spore concentration of 2 x 10(6) spores. mL(-1), pH 5.0, for 144 h cultivation. The study demonstrated not only the importance of the nature of the substrate in obtaining a system resistant to catabolic repression, but also the importance of the culture conditions for biosynthesis of this enzyme. T. viride showed a high potential for xylanase production under the conditions presented in these assays.

The influence of the sintering system on PMN properties

PMN powder samples with PbO excess of 0, 1,2 and 3% were submitted to the pressing and sintering at 1200°C for 4h with a heating rate of 3°C/min. A new sintering system, developed at our laboratories, was used. It allows obtaining more information on the sintering process. The sintered samples in the new system were compared to sintered samples in the C system. The microstructure, dielectric properties and the effect of the PbO excess in different sintering systems were compared. The N system permitted to obtain a ceramic with better properties, such density, dielectric constant and very homogeneous microstructure.

THE UBV(RI)(C) COLORS OF THE SUN

Photometric data in the UBV(RI)(C) system have been acquired for 80 solar analog stars for which we have previously derived highly precise atmospheric parameters T-eff, log g, and [Fe/H] using high-resolution, high signal-to-noise ratio spectra. UBV and (RI)(C) data for 46 and 76 of these stars, respectively, are published for the first time. Combining our data with those from the literature, colors in the UBV(RI) C system, with similar or equal to 0.01 mag precision, are now available for 112 solar analogs. Multiple linear regression is used to derive the solar colors from these photometric data and the spectroscopically derived T-eff, log g, and [Fe/H] values. To minimize the impact of systematic errors in the model-dependent atmospheric parameters, we use only the data for the 10 stars that most closely resemble our Sun, i.e., the solar twins, and derive the following solar colors: (B - V)(circle dot) = 0.653 +/- 0.005, (U - B)(circle dot) = 0.166 +/- 0.022, (V - R)(circle dot) = 0.352 +/- 0.007, and (V - I)(circle dot) = 0.702 +/- 0.010. These colors are consistent, within the 1 sigma errors, with those derived using the entire sample of 112 solar analogs. We also derive the solar colors using the relation between spectral-line-depth ratios and observed stellar colors, i.e., with a completely model-independent approach, and without restricting the analysis to solar twins. We find (B - V)(circle dot) = 0.653 +/- 0.003, (U - B)(circle dot) = 0.158 +/- 0.009, (V - R)(circle dot) = 0.356 +/- 0.003, and (V - I)(circle dot) = 0.701 +/- 0.003, in excellent agreement with the model-dependent analysis.

H. C., Wie Treitschke citiert und Geschichte schreibt [Rezension]

C.

Restriction-modification gene complexes as selfish gene entities: Roles of a regulatory system in their establishment, maintenance, and apoptotic mutual exclusion

We have reported some type II restriction-modification (RM) gene complexes on plasmids resist displacement by an incompatible plasmid through postsegregational host killing. Such selfish behavior may have contributed to the spread and maintenance of RM systems. Here we analyze the role of regulatory genes (C), often found linked to RM gene complexes, in their interaction with the host and the other RM gene complexes. We identified the C gene of EcoRV as a positive regulator of restriction. A C mutation eliminated postsegregational killing by EcoRV. The C system has been proposed to allow establishment of RM systems in new hosts by delaying the appearance of restriction activity. Consistent with this proposal, bacteria preexpressing ecoRVC were transformed at a reduced efficiency by plasmids carrying the EcoRV RM gene complex. Cells carrying the BamHI RM gene complex were transformed at a reduced efficiency by a plasmid carrying a PvuII RM gene complex, which shares the same C specificity. The reduction most likely was caused by chromosome cleavage at unmodified PvuII sites by prematurely expressed PvuII restriction enzyme. Therefore, association of the C genes of the same specificity with RM gene complexes of different sequence specificities can confer on a resident RM gene complex the capacity to abort establishment of a second, incoming RM gene complex. This phenomenon, termed “apoptotic mutual exclusion,” is reminiscent of suicidal defense against virus infection programmed by other selfish elements. pvuIIC and bamHIC genes define one incompatibility group of exclusion whereas ecoRVC gene defines another.

Structural, optical and electrical properties of sulfur-incorporated amorphous carbon films

Amorphous carbon-sulfur (a-C:S) composite films were prepared by vapor phase pyrolysis technique. The structural changes in the a-C:S films were investigated by electron microscopy. A powder X-ray diffraction (XRD) study depicts the two-phase nature of a sulfur-incorporated a-C system. The optical bandgap energy shows a decreasing trend with an increase in the sulfur content and preparation temperature. This infers a sulfur incorporation and pyrolysis temperature induced reduction in structural disorder or increase in sp (2) or pi-sites. The presence of sulfur (S 2p) in the a-C:S sample is analyzed by the X-ray photoelectron spectroscopy (XPS). The sp (3)/sp (2) hybridization ratio is determined by using the XPS C 1s peak fitting, and the results confirm an increase in sp (2) hybrids with sulfur addition to a-C. The electrical resistivity variation in the films depends on both the sulfur concentration and the pyrolysis temperature.

Resistance Mechanisms of Non-Hodgkin Lymphomas against Rituximab Treatment

Rituximab, a monoclonal antibody against B-cell specific CD20 antigen, is used for the treatment of non-Hodgkin lymphomas (NHL) and chronic lymphatic leukemia. In combination with chemotherapeutics rituximab has remarkably improved the outcome of NHL patients, but a vast variation in the lengths of remissions remains and the outcome of individual patients is difficult to predict. This thesis has searched for an explanation for this by studying the effector mechanisms of rituximab and by comparing gene expression in lymphoma tissue samples of patients with long- and short-term survival. This work demonstrated that activation of complement (C) system is in vitro more efficient effector mechanism of rituximab than cellular mechanisms or apoptosis. Activation of the C system was also shown in vivo during rituximab treatment. However, intravenously administered rituximab could not enter the cerebrospinal fluid, and neither C activation nor removal of lymphoma cells was observed in central nervous system. In vitro cytotoxicity assays showed that rituximab-induced cell killing could be markedly improved with simultaneous neutralization of the C regulatory proteins CD46 (Membrane cofactor protein), CD55 (Decay-accelerating factor), and CD59 (protectin). In a retrospective study of follicular lymphoma (FL) patients, low lymphoma tissue mRNA expressions of CD59 and CD55 were associated with a good prognosis and in a progressive flow cytometry study high expression of CD20 relative to CD55 was correlated to a longer progression free survival. Gene expression profile analysis revealed that expression of certain often cell cycle, signal transduction or immune response related genes correlate with clinical outcome of FL patients. Emphasizing the role of tumor microenvironment the best differentiating genes Smad1 and EphA1 were demonstrated to be mainly expressed in the non-malignant cells of tumors. In conclusion, this thesis shows that activation of the C system is a clinically important effector mechanism of rituximab and that microenvironment factor in tumors and expression of C regulatory proteins affect markedly the efficacy of immunochemotherapy. This data can be used to identify more accurately the patients for whom immunochemotherapy is given. It may also be beneficial in development of rituximab-containing and other monoclonal antibody therapies against cancer.

Electron transfer amongst flavo- and hemo-proteins: diffusible species effect the relay processes, not protein-protein binding

Hitherto, electron transfer (ET) between redox proteins has been deemed to occur via donor-acceptor binding, and diffusible reactive species are considered as deleterious side-products in such systems. Herein, ET from cytochrome P450 reductase (CPR, an animal membrane flavoprotein) and horseradish peroxidase (HRP, a plant hemoprotein) to cytochrome c (Cyt c, a soluble animal hemoprotein) was probed under diverse conditions, using standard assays. ET in the CPR-Cyt c system was critically inhibited by cyanide and sub-equivalent levels of polar one-electron cyclers like copper ions, vitamin C/Trolox and superoxide dismutase. In the presence of lipids, inhibition was also afforded by amphipathic molecules vitamin E, palmitoyl-vitamin C and the membrane hemoprotein, cytochrome b(5). Such nonspecific inhibition (by diverse agents in both aqueous and lipid phases) indicated that electron transfer/relay was effected by small diffusible agents, whose lifetimes are shortened by the diverse radical scavengers. When CPR was retained in a dialysis membrane and Cyt c presented outside in free solution, ET was still observed. Further, HRP (taken at nM levels) catalyzed oxidation of a phenolic substrate was significantly inhibited upon the incorporation of sub-nM levels of Cyt c. The findings imply that CPR-Cyt c or HRP-Cyt c binding is not crucial for ET. Further, fundamental quantitative arguments (based on diffusion/collision) challenge the erstwhile protein-protein binding-assisted ET hypothesis. It is proven beyond reasonable doubt that mobile and diffusible electron carriers (ions and radicals) serve as ``redox-relay agents'' in the biological ET models/setup studied.

Cyclic voltammetry of dye-modified supported bilayer lipid membranes (s-BLMs)

The voltammetric behaviour of dye-modified supported bilayer lipid membranes is investigated. (C) 1997 Elsevier Science S.A.

Gestión de la cadena de suministros desde la dinámica de sistemas. Aproximación al mejoramiento de la toma de decisiones

El objetivo de este trabajo es hacer un estudio sobre la cadena de suministros en organizaciones empresariales desde la Dinámica de Sistemas y como esta puede aportar al desempeño y el control de las cadenas de suministros. Se buscará Abordar el cocimiento sobre tres perspectivas de Supply Chain y su relación con la dinámica de sistemas. También se buscará identificar los tipos de integración en las actividades de la gestión en la cadena de suministros y sus horizontes de planeación. Por último, se pretende analizar las aplicaciones de Supply Chain Management que se han basado en el uso de la metodología de dinámica de sistemas. Para esto, la investigación empezará por definir la problemática alrededor de unir estas dos áreas y definirá el marco teórico que fundan estas dos disciplinas. Luego se abordará la metodología usada por la Dinámica de Sistemas y los diferentes aspectos de la cadena de suministros. Se Ahondará en el acercamiento de las dos disciplinas y como convergen ayudando la SD a la SCM (Supply Chain Management). En este punto también se describirán los trabajos en los diferentes enfoques que se han hecho a partir de uso de la dinámica de sistemas. Por último, presentaremos las correspondientes conclusiones y comentarios acerca de este campo de investigación y su pertinencia en el campo de la Supply Chain. Esta investigación abarca dos grandes corrientes de pensamiento, una sistémica, a través de la metodología de dinámica de sistemas y la otra, lógico analítica la cual es usada en Supply Chain. Se realizó una revisión de la literatura sobre las aplicaciones de dinámica de sistemas (SD) en el área de Supply Chain, sus puntos en común y se documentaron importantes empleos de esta metodología que se han hecho en la gestión de la cadena de suministros.

Estudo da influência da temperatura de brasagem nas uniões zircônia/aço inox 304 utilizando metalização mecânica

Metal-Ceramic (M/C) Zirconia-stainless steel interfaces have been processed through brazing techniques due to the excellent combination of properties such as high temperature stability, high corrosion resistance and good mechanical properties. However, some M/C interfaces show some defects, like porosity and cracks results in the degradation of the interfaces, leading even to its total rupture. Most of time, those defects are associated with an improper brazing parameters selection to the M/C system. In this work, ZrO2 Y-TZP and ZrO2 Mg - PSZ were joint with the stainless steel grade 304 by brazing using a eutectic silver-copper (Ag28Cu) interlayer alloy with different thermal cycles. Ceramic surfaces were previous mechanically metallized with titanium to improve adhesion of the system. The effect of temperature on the M/C interface was studied. SEM-EDS and 3 point flexural bend test were performed to evaluate morphology, chemical composition and mechanical resistance of the M/C interfaces. Lower thermal cycle temperatures produced better results of mechanical resistance, and more regular/ homogeneous reaction layers between braze alloy and metal-ceramic surfaces. Also was proved the AgCu braze alloy activation in situ by titanium

Aerobic biodegradation of butanol and diesel oil blends

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Optimization of xylanase biosynthesis by Aspergillus japonicus isolated from a Caatinga area in the Brazilian state of Bahia

The objective of this research was to investigate the potential of xylanase production by Aspergillus japonicus and to determine the effects of cultivation conditions in the process, aiming toward optimization of enzyme production. The best temperature, as well as the best carbon source, for biomass production was determined through an automated turbidimetric method (Bioscreen-C). The enzyme activity of this fungus was separately evaluated in two solid substrates (wheat and soybean bran) and in Vogel medium, adding other carbon sources. Temperature effects, cultivation time, and spore concentrations were also tested. The best temperature for enzyme and biomass production was 25°C; however, the best carbon source for growth (determined by the Bioscreen C) did not turn out to be a good inducer of xylanase production. Maximum xylanase activity was achieved when the fungus was cultivated in wheat bran (without the addition of any other carbon source) using a spore concentration of 1 × 107 spores/mL (25°C, pH 5.0, 120 h). A. japonicus is a good xylanase producer under the conditions presented in these assays. © 2006 Academic Journals.

Produção de xilanase por fungos filamentosos isolados de solo de área de caatinga

Pós-graduação em Ciências Biológicas (Microbiologia Aplicada) - IBRC

Estudo da influência das características químicas e microestruturais nas propriedades mecânicas de sistemas totalmante cerâmicos

Pós-graduação em Odontologia Restauradora - ICT