Base de dados : LILACS. Pesquisa : 529804 [Identificador único]. Referências encontradas : 1 [ref... more Base de dados : LILACS. Pesquisa : 529804 [Identificador único]. Referências encontradas : 1 [refinar]. Mostrando: 1 .. 1 no formato [Detalhado]. página 1 de 1, 1 / 1, LILACS, seleciona. para imprimir. Fotocópia. Aguiar, Claudio Lima de. Texto completo. ...
Eletrocatalisadores contendo platina, suportados em carbono de alta area superficial Vulcan XC-72... more Eletrocatalisadores contendo platina, suportados em carbono de alta area superficial Vulcan XC-72, foram sintetizados pelo metodo de reducao por alcool e testados frente a reacao de oxidacao de etanol em meio acido. Os materiais estudados foram Pt/C 20%, Pt 80 Ir 20 /C, Pt 80 W 20 /C, Pt 80 Sn 20 /C e Pt 60 Ir 10 Sn 30 /C, utilizando-se como padrao para comparacao o catalisador comercial Pt/C 20% E-TEK. A caracterizacao fisica foi realizada utilizando Energia dispersiva de raios-X (EDX), Difracao de Raios-X (DRX), Microscopia Eletronica de Transmissao (MET) e Microscopia Eletronica de varredura de alta resolucao por emissao de campo (“ Field emission electron gun ”) (MEV-FEG). As analises de EDX mostraram que as composicoes teoricas para sintese sao bem proximas dos valores experimentais. A partir dos resultados obtidos por difracao de raios-X foi possivel calcular o tamanho medio do cristalito e o parâmetro de rede das amostras estudadas. Todos os materiais apresentaram uma estrutu...
The aim of this study was to determine the optimal conditions for operating an enzyme membrane re... more The aim of this study was to determine the optimal conditions for operating an enzyme membrane reactor system to obtain a high yield of amino acids and peptides released from wheat gluten with Flavourzyme™. The optimal operating conditions were determined using multivariate analysis. A fractional factorial design made up of 27 runs amended by eight axial points was followed in a bench-scale enzyme membrane reactor system (V = 2 L), and responses were recorded over 8 h. Optimal conditions determined were a temperature of 50 ± 1 °C and a Flavourzyme™ activity of 116 ± 4 nkatLeu-pNA/mL. Modeling resulted in an optimal substrate feed rate of 19.2 g/L/h and a permeate flux of 57 L/m2/h. The enzymatic wheat gluten hydrolysis in an enzyme membrane reactor was conducted for 72 h with an average total product space–time yield of 12.6 ± 1.3 g/L/h (n = 4) and a free amino groups space–time yield of 4.4 ± 0.4 g/L/h (n = 4), and the substrate utilization was 0.82 ± 0.01 (g/g) (n = 4). The resulting product–enzyme ratios were 7.7 ± 0.6 mgTP/nkatLeu-pNA (n = 4) and 3.0 ± 0.2 mgFAA/nkatLeu-pNA (n = 4). The productivity of the enzyme membrane reactor improved compared to the reference batch process and doubled compared to previously proposed enzyme membrane reactor processes for the hydrolysis of wheat gluten.
A continuous enzymatic process for the production of the prebiotic disaccharide lactulose through... more A continuous enzymatic process for the production of the prebiotic disaccharide lactulose through transgalactosylation was developed using free and immobilized beta-glycosidase from Pyrococcus furiosus. The hyperthermostable beta-glycosidase (CelB) was immobilized onto an anion-exchange resin (Amberlite IRA-93) or onto Eupergit C with immobilization yields of 72% and 83%, respectively. The immobilized biocatalysts demonstrated specific activities of 920 nkat g(-1) dry carrier and 1500 nkat g(-1) dry carrier at 75 degrees C with p-nitrophenyl-beta-D-galactopyranoside as substrate. Continuous biotransformations in packed-bed reactors using carrier bound CelB and in an enzyme membrane reactor using free CelB were carried out at 75 degrees C. Maximum lactulose yields of 43% related to the initial lactose concentration were reached with the carrier bound CelB preparations. The corresponding productivities were 52 glactulose l(-1)h(-1) (Amberlite IRA-93) and 15 glactulose l(-1)h(-1) (Eupergit C), respectively. The free enzyme tested in an enzyme membrane reactor showed a product yield of 41% and a productivity of 12 glactulose l(-1)h(-1) in the first day. While both carrier bound CelB preparations were 100% stable for at least 14 days, the half-life of the free CelB in the enzyme membrane reactor was only about 1.5 days.
ABSTRACT The electrooxidation of 0.1 M 1-propanol and 2-propanol in 0.1 M HClO4 on smooth Pt and ... more ABSTRACT The electrooxidation of 0.1 M 1-propanol and 2-propanol in 0.1 M HClO4 on smooth Pt and electrodeposited Pt and Pt0.89Ru0.11 was studied by cyclic voltammetry and in situ Fourier transform infrared spectroscopy (FTIRS). On smooth Pt, CO2 as well as partially oxidized products (propionic acid from l-propanol and acetone from 2-propanol) was detected. A strong catalytic enhancement toward the oxidation to CO2 is observed on electrodeposited Pt for both 2-propanol and 1-propanol, thus showing the effect of the roughness of the electrode on the electrooxidation process. However, propionic acid from 1-propanol and acetone from 2-propanol were still detected. In contrast to these results, CO2 was the only oxidation product on Pt-0.89-Ru-0.11 for both alcohols.
Phenolic compounds detection in fruit extracts from: açai, bacuri, buriti, blackberry, black mulb... more Phenolic compounds detection in fruit extracts from: açai, bacuri, buriti, blackberry, black mulberry, blueberry, juçara, physalis, raspberry, and tamarillo, have been performed by reverse-phase high performance liquid chromatography with electrochemical detection (RP-HPLC-EC), using two detectors in series: a wall-jet detector flow cell with a glassy carbon electrode, and a thin-layer flow cell detector with a boron doped diamond electrode. This methodology, in gradient elution mode, was successfully used to detect seventeen phenolic compounds in the fruit extracts. The total antioxidant capacity of the fruit extracts by the electrochemical quantitative index (EI) and the method of capture of diphenilpicrilhydrazil (DPPH(●)) free radical "efficient concentration" (EC50), was evaluated. A very good correlation between EI and EC50 assays has been obtained, the fruit with the highest total antioxidant capacity being blackberry, while physalis exhibited the lowest antioxidant...
Base de dados : LILACS. Pesquisa : 529804 [Identificador único]. Referências encontradas : 1 [ref... more Base de dados : LILACS. Pesquisa : 529804 [Identificador único]. Referências encontradas : 1 [refinar]. Mostrando: 1 .. 1 no formato [Detalhado]. página 1 de 1, 1 / 1, LILACS, seleciona. para imprimir. Fotocópia. Aguiar, Claudio Lima de. Texto completo. ...
Eletrocatalisadores contendo platina, suportados em carbono de alta area superficial Vulcan XC-72... more Eletrocatalisadores contendo platina, suportados em carbono de alta area superficial Vulcan XC-72, foram sintetizados pelo metodo de reducao por alcool e testados frente a reacao de oxidacao de etanol em meio acido. Os materiais estudados foram Pt/C 20%, Pt 80 Ir 20 /C, Pt 80 W 20 /C, Pt 80 Sn 20 /C e Pt 60 Ir 10 Sn 30 /C, utilizando-se como padrao para comparacao o catalisador comercial Pt/C 20% E-TEK. A caracterizacao fisica foi realizada utilizando Energia dispersiva de raios-X (EDX), Difracao de Raios-X (DRX), Microscopia Eletronica de Transmissao (MET) e Microscopia Eletronica de varredura de alta resolucao por emissao de campo (“ Field emission electron gun ”) (MEV-FEG). As analises de EDX mostraram que as composicoes teoricas para sintese sao bem proximas dos valores experimentais. A partir dos resultados obtidos por difracao de raios-X foi possivel calcular o tamanho medio do cristalito e o parâmetro de rede das amostras estudadas. Todos os materiais apresentaram uma estrutu...
The aim of this study was to determine the optimal conditions for operating an enzyme membrane re... more The aim of this study was to determine the optimal conditions for operating an enzyme membrane reactor system to obtain a high yield of amino acids and peptides released from wheat gluten with Flavourzyme™. The optimal operating conditions were determined using multivariate analysis. A fractional factorial design made up of 27 runs amended by eight axial points was followed in a bench-scale enzyme membrane reactor system (V = 2 L), and responses were recorded over 8 h. Optimal conditions determined were a temperature of 50 ± 1 °C and a Flavourzyme™ activity of 116 ± 4 nkatLeu-pNA/mL. Modeling resulted in an optimal substrate feed rate of 19.2 g/L/h and a permeate flux of 57 L/m2/h. The enzymatic wheat gluten hydrolysis in an enzyme membrane reactor was conducted for 72 h with an average total product space–time yield of 12.6 ± 1.3 g/L/h (n = 4) and a free amino groups space–time yield of 4.4 ± 0.4 g/L/h (n = 4), and the substrate utilization was 0.82 ± 0.01 (g/g) (n = 4). The resulting product–enzyme ratios were 7.7 ± 0.6 mgTP/nkatLeu-pNA (n = 4) and 3.0 ± 0.2 mgFAA/nkatLeu-pNA (n = 4). The productivity of the enzyme membrane reactor improved compared to the reference batch process and doubled compared to previously proposed enzyme membrane reactor processes for the hydrolysis of wheat gluten.
A continuous enzymatic process for the production of the prebiotic disaccharide lactulose through... more A continuous enzymatic process for the production of the prebiotic disaccharide lactulose through transgalactosylation was developed using free and immobilized beta-glycosidase from Pyrococcus furiosus. The hyperthermostable beta-glycosidase (CelB) was immobilized onto an anion-exchange resin (Amberlite IRA-93) or onto Eupergit C with immobilization yields of 72% and 83%, respectively. The immobilized biocatalysts demonstrated specific activities of 920 nkat g(-1) dry carrier and 1500 nkat g(-1) dry carrier at 75 degrees C with p-nitrophenyl-beta-D-galactopyranoside as substrate. Continuous biotransformations in packed-bed reactors using carrier bound CelB and in an enzyme membrane reactor using free CelB were carried out at 75 degrees C. Maximum lactulose yields of 43% related to the initial lactose concentration were reached with the carrier bound CelB preparations. The corresponding productivities were 52 glactulose l(-1)h(-1) (Amberlite IRA-93) and 15 glactulose l(-1)h(-1) (Eupergit C), respectively. The free enzyme tested in an enzyme membrane reactor showed a product yield of 41% and a productivity of 12 glactulose l(-1)h(-1) in the first day. While both carrier bound CelB preparations were 100% stable for at least 14 days, the half-life of the free CelB in the enzyme membrane reactor was only about 1.5 days.
ABSTRACT The electrooxidation of 0.1 M 1-propanol and 2-propanol in 0.1 M HClO4 on smooth Pt and ... more ABSTRACT The electrooxidation of 0.1 M 1-propanol and 2-propanol in 0.1 M HClO4 on smooth Pt and electrodeposited Pt and Pt0.89Ru0.11 was studied by cyclic voltammetry and in situ Fourier transform infrared spectroscopy (FTIRS). On smooth Pt, CO2 as well as partially oxidized products (propionic acid from l-propanol and acetone from 2-propanol) was detected. A strong catalytic enhancement toward the oxidation to CO2 is observed on electrodeposited Pt for both 2-propanol and 1-propanol, thus showing the effect of the roughness of the electrode on the electrooxidation process. However, propionic acid from 1-propanol and acetone from 2-propanol were still detected. In contrast to these results, CO2 was the only oxidation product on Pt-0.89-Ru-0.11 for both alcohols.
Phenolic compounds detection in fruit extracts from: açai, bacuri, buriti, blackberry, black mulb... more Phenolic compounds detection in fruit extracts from: açai, bacuri, buriti, blackberry, black mulberry, blueberry, juçara, physalis, raspberry, and tamarillo, have been performed by reverse-phase high performance liquid chromatography with electrochemical detection (RP-HPLC-EC), using two detectors in series: a wall-jet detector flow cell with a glassy carbon electrode, and a thin-layer flow cell detector with a boron doped diamond electrode. This methodology, in gradient elution mode, was successfully used to detect seventeen phenolic compounds in the fruit extracts. The total antioxidant capacity of the fruit extracts by the electrochemical quantitative index (EI) and the method of capture of diphenilpicrilhydrazil (DPPH(●)) free radical "efficient concentration" (EC50), was evaluated. A very good correlation between EI and EC50 assays has been obtained, the fruit with the highest total antioxidant capacity being blackberry, while physalis exhibited the lowest antioxidant...
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