Sequencing of Spodoptera frugiperda midgut trehalases and demonstration of secretion of soluble trehalase by midgut columnar cells

Both soluble (SfTre1) and membrane-bound (SfTre2) trehalases occur along the midgut of Spodoptera frugiperda larvae. Released SfTre2 was purified as a 67 kDa protein. Its K(m) (1.6 mM) and thermal stability (half life 10 min at 62 degrees C) are different from the previously isolated soluble trehalase (K(m) = 0.47 mM; 100% stable at 62 degrees C). Two cDNAs coding for S. frugiperda trehalases have been cloned using primers based on consensus sequences of trehalases and having as templates a cDNA library prepared from total polyA-containing RNA extracted from midguts. One cDNA codes for a trehalase that has a predicted transmembrane sequence and was defined as SfTre2. The other, after being cloned and expressed, results in a recombinant trehalase with a K(m) value and thermal stability like those of native soluble trehalase. This enzyme was defined as SfTre1 and, after it was used to generate antibodies, it was immunolocalized at the secretory vesicles and at the glycocalyx of columnar cells. Escherichia coli trehalase 3D structure and sequence alignment with SfTre1 support a proposal regarding the residue modulating the pKa value of the proton donor.

Purification and preliminary crystallographic analysis of a new Lys49-PLA2 from B-jararacussu

BjVIII is a new myotoxic Lys49-PLA2 isolated from Bothrops jararacussu venom that exhibits atypical effects on human platelet aggregation. To better understand the mode of action of BjVIII, crystallographic studies were initiated. Two crystal forms were obtained, both containing two molecules in the asymmetric unit (ASU). Synchrotron radiation diffraction data were collected to 2.0 angstrom resolution and 1.9 angstrom resolution for crystals belonging to the space group P2(1)2(1)2(1) (a = 48.4 angstrom, b = 65.3 angstrom, c = 84.3 angstrom) and space group P3(1)21 (a = b = 55.7 angstrom, c = 127.9 angstrom), respectively. Refinement is currently in progress and the refined structures are expected to shed light on the unusual platelet aggregation activity observed for BjVIII.

Desempenho de um aquecedor de água a biogás

Estudos foram desenvolvidos para dimensionar e adaptar o injetor do queimador principal de um aquecedor de água tipo acumulação de 75 L. O diâmetro do injetor foi redimensionado em função da pressão de serviço de 100 mm H2O e poder calorífico inferior do biogás de 21.600 kJ m-3 n, garantindo a manutenção da potência calorífica do equipamento de 20.900 kJ h-1. Os resultados demonstraram que o queimador adaptado operou com biogás adequadamente, com chama estável. A eficiência média do aquecedor foi de 68%, para ganho térmico de 36,7 ºC, correspondendo à temperatura final da água igual a 62,7 ºC, sendo consumido 0,796 m³n de biogás, aquecendo 75 L de água em 72 minutos.

Dehydration of dedo de moça pepper: kinetics and phytochemical concentration

A pimenta vermelha é rica em vitamina C e outros fitoquímicos e pode ser consumida como produto desidratado. A avaliação das melhores condições de secagem pode garantir melhor qualidade do produto. Assim, o objetivo deste trabalho foi estudar o efeito da temperatura do ar de secagem (55, 65, 75 ºC) sobre a cinética de secagem, conteúdos de vitamina C e fenólicos totais e cor do produto desidratado, comparando-os à pimenta in natura. A desidratação foi feita por convecção forçada em estufa. A cinética de secagem foi determinada por pesagens periódicas até peso constante. A umidade da pimenta in natura foi de aproximadamente 86%. As curvas de secagem foram ajustadas por três modelos diferentes, avaliados na literatura. O modelo de Page apresentou o melhor ajuste para este processo. A análise de variância mostrou que a temperatura de secagem influenciou significativamente (p < 0,05) os parâmetros de qualidade (conteúdo de vitamina C, conteúdo de fenólicos totais, cor) da pimenta desidratada quando comparados aos da pimenta in natura. Após a secagem, a retenção de vitamina C aumentou com a redução da temperatura de secagem. de maneira geral, a qualidade do produto foi favorecida na secagem com menor temperatura, devido à redução nas perdas de compostos bioativos.

Dexamethasone-induced insulin resistance is associated with increased connexin 36 mRNA and protein expression in pancreatic rat islets

Augmented glucose-stimulated insulin secretion (GSIS) is an adaptive mechanism exhibited by pancreatic islets from insulin-resistant animal models. Gap junction proteins have been proposed to contribute to islet function. As such, we investigated the expression of connexin 36 (Cx36), connexin 43 (Cx43), and the glucose transporter Glut2 at mRNA and protein levels in pancreatic islets of dexamethasone (DEX)-induced insulin-resistant rats. Study rats received daily injections of DEX (1 mg/kg body mass, i.p.) for 5 days, whereas control rats (CTL) received saline solution. DEX rats exhibited peripheral insulin resistance, as indicated by the significant postabsorptive insulin levels and by the constant rate for glucose disappearance (K-ITT). GSIS was significantly higher in DEX islets (1.8-fold in 16.7 mmol/L glucose vs. CTL, p < 0.05). A significant increase of 2.25-fold in islet area was observed in DEX vs. CTL islets (p < 0.05). Cx36 mRNA expression was significantly augmented, Cx43 diminished, and Glut2 mRNA was unaltered in islets of DEX vs. CTL (p < 0.05). Cx36 protein expression was 1.6-fold higher than that of CTL islets (p < 0.05). Glut2 protein expression was unaltered and Cx43 was not detected at the protein level. We conclude that DEX-induced insulin resistance is accompanied by increased GSIS and this may be associated with increase of Cx36 protein expression.

Desenvolvimento de misturas instantâneas de mandioca e caseína: efeito do teor de proteína e parâmetros de extrusão sobre a viscosidade

O interesse da indústria de alimentos por produtos desenvolvidos a partir de farinhas acrescidas de proteína não se deve somente às suas características nutricionais, senão também às suas propriedades funcionais e reológicas, as quais definem as suas aplicações comerciais. Este trabalho teve por objetivo avaliar o efeito de parâmetros operacionais do processo de extrusão sobre as propriedades de pasta de misturas de farinha de mandioca e caseína. O processo de extrusão seguiu o delineamento 'central composto rotacional' para três fatores: teor de proteína (2,5 a 9,5%), umidade (14,5 a 19,5%) e temperatura de extrusão (65 a 135 ºC). As misturas antes e após a extrusão foram analisadas no Rapid Visco Analyser (RVA) quanto a: viscosidade inicial, pico de viscosidade, quebra de viscosidade, viscosidade final e tendência à retrogradação. Os resultados obtidos nas misturas antes da extrusão mostraram aumento dos valores de viscosidade com o aumento da concentração de proteína até o ponto central (6%) e, nos teores mais elevados de proteína, ocorreu redução destes. Após a extrusão, observou-se que o teor de proteína foi a variável de maior efeito sobre as propriedades de pasta, seguida pela umidade das misturas.

Influence of Different Substrates on the Production of a Mutant Thermostable Glucoamylase in Submerged Fermentation

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

Friction factors and rheological properties of orange juice

The rheological behavior of Brazilian orange juice with different water content (0.34-0.73 w/w) was studied at a wide range of temperatures (0.5-62 degrees C) using a concentric cylinder viscometer. The results indicated that the juices behave as pseudoplastic fluids with yield stress, being represented by the Herschel-Bulkley model. The rheological parameters were fitted as functions of both temperature and water content in the tested range. Based on dimensional analysis it was proposed a modified Reynolds number (Re-M), which includes the Herschel-Bulkley parameters. Experimental data of friction factors during heating and cooling processes of orange juice in laminar flow through circular tubes could be well correlated as a function of Re-M. (C) 1999 Elsevier B.V. Ltd. All rights reserved.

Low temperature synthesis and electrical properties of PbTiO3 thin films prepared by the polymeric precursor method

Ferroelectric PbTiO3 thin films were successfully prepared on a Pt(111)Ti/SiO2/Si(100) substrate for the first time by spin coating, using the polymeric precursor method. X-ray diffraction patterns of the films indicate that they are polycrystalline in nature. This method allows low temperature (500 degrees C) synthesis and high electrical properties. The multilayer PbTiO3 thin films were granular in structure with a grain size of approximately 110-120 nm. A 380-nm-thick film was obtained by carrying out four cycles of the spin-coating/heating process. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses showed the surface of these thin films to be smooth, dense and crack-free with low surface roughness (=3.4 nm). At room temperature and at a frequency of 100 kHz, the dielectric constant and the dissipation factor were, respectively, 570 and 0.016. The C-V characteristics of perovskite thin film prepared at low temperature show normal ferrolectric behavior. The remanent polarization and coercive field for the films deposited were 13.62 mu C/cm(2) and 121.43 kV/cm, respectively. The high electrical property values are attributed to the excellent microstrutural quality and chemical homogeneity of thin films obtained by the polymeric precursor method. (C) 2000 Elsevier B.V. S.A. All rights reserved.

A metodologia de superfície de resposta como ferramenta para a avaliação da produção de alginato e poli-hidroxibutirato pela Azotobacter vinelandii

The response surface methodology as a tool for assessing the production of alginate and polyhydroxybutirate by Azotobacter vinelandii. Alginate is a polysaccharide extracted from cell walls of brown algae and used in the food, pharmaceuticals and biotech industries. Production is concentrated on the cultivation of brown seaweed, but several bacteria of the genus Pseudomonas and Azotobacter produce alginate. The chemical structure of alginates produced by algae is similar to those synthesized by A. vinelandii. The bacteria also produce intracellular polymers such as polyhydroxybutyrate (PHB), known as bioplastic. This work studied the simultaneous alginate and PHB production by A. vinelandii using sucrose and different parameters of fermentation in an orbital shaker. The optimal values for the production of these compounds were determined by the MSR. The first experiment was a 2(6-2) factorial design. The second was based on significant variables of the first, resulting in a full 3(3-0) factorial design. From the first to the second, an increase was observed in the PHB productivity from 12 to 45 mg g(-1) cell h(-1) and alginate from 100 to 1,600 mg g(-1) of cell h(-1). The productivity of both compounds was in the maximum incubation temperature of 62 degrees C, in the shortest time of incubation (18h) and the sucrose concentration, 11 g L(-1). In both experiments the PHB extracted presented purity of 94%.

Xylanase and β-Xylosidase from Penicillium janczewskii: Production, Physico-Chemical properties, and application of the crude extract to pulp biobleaching

Extracellular xylanase and β-xylosidase production by a Penicillium janczewskii strain were investigated in liquid cultures with xylan from oat spelts under different physical and chemical conditions. The selected conditions for optimized production of xylanase and β-xylosidase were 7 days, pH 6.5, at 30 °C and 8 days, pH 5.0, at 25 °C, respectively. The xylanase exhibited optimal activity in pH 5.0 at 50 °C and the β- xylosidase in pH 4.0 at 75 °C. The xylanase was more stable at pH 6.0 to 9.5, while the β-xylosidase remained stable at pH ranging from 1.6 to 5.5. The xylanase half-life (T50) at 40, 50, and 60 °C was 183, 15, and 3 min, respectively. β-xylosidase half-life was 144, 8, and 4 min at 50, 65, and 75 °C, respectively. When applied to the biobleaching of Eucalyptus kraft pulp, xylanase dosages of 2 and 4 U/g dried pulp reduced, respectively, kappa number by 3.0 and 3.3 units after 1 h treatment, demonstrating that the use of P. janczewskii xylanases in this process is quite promising. The pulp viscosity was not altered, confirming the absence of cellulolytic enzymes in the fungal extract.

Produção e caracterização do complexo xilanolítico de Penicillium janczewskii

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudos estruturais de uma lectina presente em sementes de Lotus tetragonolobus

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Characterization of the co-purified invertase and beta-glucosidase of a multifunctional extract from Aspergillus terreus

The filamentous fungus Aspergillus terreus secretes both invertase and beta-glucosidase when grown under submerged fermentation containing rye flour as the carbon source. The aim of this study was to characterize the co-purified fraction, especially the invertase activity. An invertase and a beta-glucosidase were co-purified by two chromatographic steps, and the isolated enzymatic fraction was 139-fold enriched in invertase activity. SDS-PAGE analysis of the co-purified enzymes suggests that the protein fraction with invertase activity was heterodimeric, with subunits of 47 and 27 kDa. Maximal invertase activity, which was determined by response surface methodology, occurred in pH and temperature ranges of 4.0-6.0 and 55-65 A degrees C, respectively. The invertase in co-purified enzymes was stable for 1 h at pH 3.0-10.0 and maintained full activity for up to 1 h at 55 A degrees C when diluted in water. Invertase activity was stimulated by 1 mM concentrations of Mn2+ (161 %), Co2+ (68 %) and Mg2+ (61 %) and was inhibited by Al3+, Ag+, Fe2+ and Fe3+. In addition to sucrose, the co-purified enzymes hydrolyzed cellobiose, inulin and raffinose, and the apparent affinities for sucrose and cellobiose were quite similar (K-M = 22 mM). However, in the presence of Mn2+, the apparent affinity and V-max for sucrose hydrolysis increased approximately 2- and 2.9-fold, respectively, while for cellobiose, a 2.6-fold increase in V-max was observed, but the apparent affinity decreased 5.5-fold. Thus, it is possible to propose an application of this multifunctional extract containing both invertase and beta-glucosidase to degrade plant biomass, thus increasing the concentration of monosaccharides obtained from sucrose and cellobiose.

Crystallization and preliminary X-ray diffraction analysis of a novel sphingomyelinase D from Loxosceles gaucho venom

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)