Influence of activation on the multipoint immobilization of penicillin G acylase on macroporous silica

Penicillin G acylase is the second most important enzyme used by industry in an immobilized form. Penicillin hydrolysis is its main application. This reaction is used to produce 6-aminopenicillanic acid (6-APA), an intermediate in the synthesis of semisynthetic antibiotics. This work aims to compare catalytic properties of different penicillin G acylase (PGA) derivatives obtained by multipoint immobilization of the enzyme on macroporous silica. Enzyme amino groups react with different aldehyde groups produced in the support using either glutaraldehyde or glyoxyl activation. In the former method, silica reacts with g-aminopropyltriethoxysilane (g-APTS) and glutaraldehyde; in the latter, a reaction with glycidoxypropyltrimethoxysilane (GPTMS) is followed by acid hydrolysis and oxidation using sodium periodate. This work determines the influence of degree of activation, using glutaraldehyde, on immobilization parameters. PGA was immobilized on these two different supports. Maximum enzyme load, immobilized enzyme activity (derivative activity), rate of immobilization and thermal stability were checked for both cases. For glutaraldehyde activation, the results showed that 0.5% of the g-APTS is sufficient for all the hydroxyl groups in the silica to react. They also showed that degree of activation only affects immobilization yield and reaction velocity and that reduction of the glutaraldehyde derivatives with sodium borohydride does not affect their thermal stability. In comparing the derivatives obtained using glyoxyl and glutaraldehyde activation, it was observed that the glyoxyl derivatives presented better immobilization parameters, with a maximum enzyme load of 264 IU/g silica and a half-life of 20 minutes at 60 °C.

Construction and application of an electrochemical sensor for paracetamol determination based on iron tetrapyridinoporphyrazine as a biomimetic catalyst of P450 enzyme

This work describes the construction and application of a biomimetic sensor for paracetamol determination in different samples. The sensor was prepared by modifying a glassy carbon electrode surface with a Nafion (R) membrane doped with FeTPyPz. The best performance of the sensor in 0.1 mol L-1 acetate buffer was at pH 3.6. Under these conditions, an oxidation potential of paracetamol was observed at 445 mV vs. Ag vertical bar AgCl. The sensor presented a linear response range between 4.0 and 420 mu mol L-1, a sensitivity of 46.015 mA L mol(-1) cm(-2), quantification and detection limits of 4.0 mu mol L-1 and 1.2 mu mol L-1, respectively. A detailed investigation about its electrochemical behavior and selectivity was carried out. The results suggested that FeTPyPz presents catalytic properties similar to P450 enzyme for paracetamol oxidation. Finally, the sensor was applied for paracetamol determination in commercial drugs and for the monitoring of its degradation in an electrochemical batch reactor effluent.

Influence of Cu(II) in the SrSnO3 crystallization

Perovskite type oxides have been intensively studied due to their interesting optical, electrical, and catalytic properties. Among perovskites the alkaline earth stannates stand out, being strontium stannates (SrSnO3) the most important material in ceramic technology among them due to their wide application as dielectric component. SrSnO3 has also been applied as stable capacitor and humidity sensor. In the present work, SrSnO3:Cu was synthesized by polymeric precursor method and heat treated at 700, 800, and 900 A degrees C for 4 h. After that, the material was characterized by thermal analysis (TG/DTA), X-ray diffraction (XRD), infrared spectroscopy, and UV-vis spectroscopy. Results indicated three thermal decomposition steps and confirmed the presence of strontium carbonate and Cu2+ reduction to Cu+ at higher dopant amounts. XRD patterns indicated that the perovskite crystallization started at 700 A degrees C with strontiatite (SrCO3) and cassiterite (SnO2) as intermediate phases, disappearing at higher temperatures. The amount of secondary phase was reduced with the increase in the Cu concentration.

A comparative study of glycerol dehydration catalyzed by micro/mesoporous MFI zeolites

The catalytic properties of monomodal microporous and bimodal micro-mesoporous zeolites were investigated in the gas-phase dehydration of glycerol. The desilication methodology used to produce the mesoporous zeolites minimized diffusion limitations and increased glycerol conversion in the catalytic reaction due to the hierarchical system of secondary pores created in the zeolite crystals. The chemical and structural properties of the catalyst were studied by X-ray diffraction, nitrogen adsorption-desorption isotherms, NH3-TPD and pyridine chemisorption followed by IR-spectroscopy. Although the aim was to desilicate to create mesoporosity in the zeolite crystals, the desilication promoted the formation of extra-framework aluminum species that affected the conversion of glycerol and the products distribution. The results clearly show that the mesoporous zeolites with designed mesopore structure allowed a rapid diffusion and consequently improved the reaction kinetics. However, especial attention must be given to the desilication procedure because the severity of the treatment negatively interfered on the Brønsted and Lewis acid sites relative concentration and, consequently, in the efficiency of the catalysis performed by these materials. On the other hand, during the catalytic reaction, the intracrystalline mesopores allowed carbonaceous compounds to be deposited herein, resulting in less blocked micropores and catalysts with higher long-term stability.

Effect of the ZrO2 phase on the structure and behavior of supported Cu catalysts for ethanol conversion

The effect of amorphous (am-), monoclinic (m-), and tetragonal (t-) ZrO2 phase on the physicochemical and catalytic properties of supported Cu catalysts for ethanol conversion was studied. The electronic parameters of Cu/ZrO2 were determined by in situ XAS, and the surface properties of Cu/ZrO2 were defined by XPS and DRIFTS of CO-adsorbed. The results demonstrated that the kind of ZrO2 phase plays a key role in the determination of structure and catalytic properties of Cu/ZrO 2 catalysts predetermined by the interface at Cu/ZrO2. The electron transfer between support and Cu surface, caused by the oxygen vacancies at m-ZrO2 and am-ZrO2, is responsible for the active sites for acetaldehyde and ethyl acetate formation. The highest selectivity to ethyl acetate for Cu/m-ZrO2 catalyst up to 513 K was caused by the optimal ratio of Cu0/Cu+ species and the high density of basic sites (O2-) associated with the oxygen mobility from the bulk m-ZrO2. © 2013 Elsevier Inc. All rights reserved.

Transformação do glicerol em compostos de interesse petroquímico catalisada por zeólitas com ordem hierárquica de poros

Pós-graduação em Química - IQ

Bidestilação em alambiques contendo dispositivos de prata e cobre e sua influência na qualidade da cachaça

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

Síntese e caracterização de nanocatalisadores 'PtV'/C e 'PtCr'/C para cátodos de células a combustível de baixa temperatura

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Formação e crescimento de nanopartículas de óxido de zinco via sol-gel

Pós-graduação em Química - IQ

Bromophenol blue discoloration using peroxidase immobilized on highly activated corncob powder

The aim of the present study was to evaluate the efficacy of peroxidase immobilized on corncob powder for the discoloration of dye. Peroxidase was extracted from soybean seed coat, followed by amination of the surface of the tertiary structure. The aminated peroxidase was immobilized on highly activated corncob powder and employed for the discoloration of bromophenol blue. Amination was performed with 10 or 50 mmol.L-1carbodiimide and 1 mol.L-1ethylenediamine. The amount of protein in the extract was 0.235 ± 0.011 mg.mL-1and specific peroxidase activity was 86.06 ± 1.52 µmol min-1.mg-1, using 1 mmol.L-1ABTS as substrate. Ten mmol.L-1and 50 mmol.L-1 aminated peroxidase retained 88 and 100% of the initial activity. Following covalent immobilization on a corncob powder-glyoxyl support, 10 and 50 mmol.L-1aminated peroxidase retained 74 and 86% of activity, respectively. Derivatives were used for the discoloration of 0.02 mmol.L-1bromophenol blue solution. After 30 min, 93 and 89% discoloration was achieved with the 10 mmol.L-1and 50 mmol.L-1derivatives, respectively. Moreover, these derivatives retained 60% of the catalytic properties when used three times. Peroxidase extracted from soybean seed coat immobilized on a low-cost corncob powder support exhibited improved thermal stability. Keywords: Peroxidases. Multipoint immobilization of enzymes. Aminated enzymes. Corncob powder. RESUMO Descoloração de azul de bromofenol utilizando peroxidase imobilizada em pó de sabugo de milho altamente ativado Nesta pesquisa a enzima peroxidase foi extraída do tegumento de sementes de soja, e a superfície da estrutura terciária foi aminada. A peroxidase aminada foi imobilizada em suporte pó de sabugo de milho altamente ativado e utilizado na descoloração de azul de bromofenol. A aminação da peroxidase foi realizada com carbodiimida em concentrações de 10 e 50 mmol.L-1, e 1 mol.L-1de etilenodiamina. A quantidade de proteínas no extrato foi de 0,235 ± 0,011 mg.mL-1, e a atividade específica da peroxidase foi 86,06 ± 1,52 µmol min-1.mg-1, usando 1 mmol.L-1de ABTS como substrato. A peroxidase aminada a 10 mmol.L-1reteve 88% e a aminada a 50 mmol.L-1reteve 100% da atividade inicial. As peroxidases aminadas a 10 ou 50 mmol.L-1foram covalentemente imobilizadas em suporte glioxil-pó de sabugo de milho com atividade recuperada de 74% e 86%, respectivamente. Os derivados obtidos foram utilizados na descoloração de solução de azul de bromofenol 0,02 mmol.L-1. Após 30 min 93% de descoloração foram alcançados com o derivado glioxil-pó de sabugo de milho com a peroxidase aminada 10 mmol.L-1e 89% com a aminada 50 mmol.L-1. Estes derivados mantiveram 60% das propriedades catalíticas, quando utilizado por três vezes. A peroxidase extraída do tegumento da semente de soja imobilizada em suporte de baixo custo pó de sabugo de milho apresentou melhoria na estabilidade térmica da enzima. Palavras-chave: Peroxidases. Imobilização multipontual de enzimas. Aminação de enzimas. Pó de sabugo de milho.

Processo de destilação para redução de contaminação por carbamato de etila em bebidas alcoólicas

Contamination of Brazilian sugar-cane rum by ethyl carbamate, a potentially carcinogenic substance, is considered an obstacle to export of the beverage. Copper is involved in ethyl-carbamate-formation reactions, and the replacement thereof by stainless steel in distillation equipment, with the aim of preventing the formation of said compound, results in a beverage of poor sensory quality owing to the presence of dimethyl sulphide. A reduction in the concentration of sulphurated compounds in the final product may be achieved by the placing of a copper device (Patent No. 8206688) inside the dome of a stainless-steel alembic. It is therefore appropriate to verify the efficiency of using other forms of catalysts that, in addition to reducing ethyl-carbamate levels, are able, likewise, to trigger other catalytic actions that allow the production of a distillate of good sensory quality. Silver is the noble metal most used in industry and, on account of the catalytic properties thereof, it is ideal for use as a catalyst in oxidation reactions. The subject matter of the present invention comprises a method involving the use of silver in the distillation of alcoholic beverages, such as sugar-cane rum, which reduces ethyl-carbamate contamination of the end-product.

DFT Study on Ce-Doped Anatase TiO2: Nature of Ce3+ and Ti3+ Centers Triggered by Oxygen Vacancy Formation

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

Síntese de nanocatalisador cerâmico a base de SnO2 pelo método hidrotermal assistido por micro-ondas aplicado a reação de transesterificação do óleo de babaçu

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

As-synthesized TEA-BEA zeolite: Effect of Si/Al ratio on the Knoevenagel condensation

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Bromofhenol blue discoloration using peroxidase immobilized on highly activated corncob powder

The aim of the present study was to evaluate the efficacy of peroxidase immobilized on corncob powder for the discoloration of dye. Peroxidase was extracted from soybean seed coat, followed by amination of the surface of the tertiary structure. The aminated peroxidase was immobilized on highly activated corncob powder and employed for the discoloration of bromophenol blue. Amination was performed with 10 or 50 mmol.L-1 carbodiimide and 1 mol.L-1 ethylenediamine. The amount of protein in the extract was 0.235 ± 0.011 mg.mL-1 and specific peroxidase activity was 86.06 ± 1.52 µmol min-1 . mg-1, using 1 mmol.L-1 ABTS as substrate. Ten mmol.L-1 and 50 mmol.L-1 aminated peroxidase retained 88 and 100% of the initial activity. Following covalent immobilization on a corncob powder-glyoxyl support, 10 and 50 mmol.L-1 aminated peroxidase retained 74 and 86% of activity, respectively. Derivatives were used for the discoloration of 0.02 mmol.L-1 bromophenol blue solution. After 30 min, 93 and 89% discoloration was achieved with the 10 mmol.L-1 and 50 mmol.L-1 derivatives, respectively. Moreover, these derivatives retained 60% of the catalytic properties when used three times. Peroxidase extracted from soybean seed coat immobilized on a low-cost corncob powder support exhibited improved thermal stability.