Utilização de resíduos agroindustriais para a produção de proteases pelo termofílico Bacillus sp em fermentação submersa: otimização do meio de cultura usando a técnica de planejamento experimental

Thermophilic Bacillus sp. SMIA-2, produced protease when grown on apple pectic, whey protein and corn step liquor medium, whose concentration was varied from 3 to 10 gL-1, according to the central composite design 2³. The experiments were conducted in shaker, at 50 °C, 150 rpm and initial pH 6.5. The results revealed that the culture medium affected both, cell growth and enzyme production. After graphical and numerical optimization procedure, the enzyme production reached its maximum value at 30 h fermentation, reaching, approximately, 70 U protein mg-1, suggesting that this process was partially associated to the growth.

Avaliação do desempenho de surfactantes para a solubilização de fases líquidas não aquosas em meio aquoso

The presence of non-aqueous phase liquids (NAPLs) in the subsurface is a threat to public health as well as a serious environmental issue. NAPLs may remain adsorbed or form lenses floating on aquifers causing long-term contaminations. Surfactants may increase NAPLs solubility, enhancing the pump-and-treatment performance. Size, shape, hydration and ionization degree of the micelles define the affinity and the space available for the solubilization of a particular contaminating agent. The tests carried out at laboratory scale, taking into account the NAPL to be removed and the medium characteristics were useful to select surfactants and evaluate their efficiency as NAPLs solubilizers.

Produção de poli(3-hidroxibutirato) por Cupriavidus Necator em meio hidrolisado de amido de arroz com suplementação de óleo de soja em diferentes temperaturas

Poly (3-hydroxybutyrate) (P(3HB)) is a biopolymer, completely biodegradable, which has similar properties to fuel-based polymers. However to make it economically competitive it is necessary the study of cheap sources of substrate. The influence of hydrolyzed rice starch supplemented with soybean oil at different temperatures (30, 35 and 40 °C) was studied in the production of P(3HB) by C. necator. The percentage of P(3HB) produced in the cultures at 30, 35 °C was 30, 39% and 35, 43% without and with supplementation of oil, respectively. The culture at 40 °C showed no production phase due to a possible oxygen limitation. These results demonstrate that hydrolyzed rice starch supplemented with soybean oil increases the yield of P(3HB) and temperature of 35 ºC is the most favorable for biopolymer production.

Reaproveitamento de óxidos de manganês de pilhas descartadas para eletrocatálise da reação de redução de oxigênio em meio básico

The oxygen reduction reaction was studied in alkaline media using manganese oxides obtained from spent batteries as electrocatalysts. Three processes were used to recover manganese oxides from spent batteries. The particles obtained were in the range from 8 to 11 nm. The electrochemical experiments indicated a good electrocatalytic activity toward oxygen reduction using the different samples and showing approximately a direct transference of 4 electrons during the process. Even though all the processes were efficient, the best result was observed for the prepared sample using reactants of low cost.

A formação inicial em química baseada em conceitos representados por meio de modelos mentais

The current legislation determines that the chemist must have a solid comprehension about chemical concepts. Literature presents the concept of mental model, which is determinant to the learning of phenomena and concepts. This paper presents some mental models that students of the Chemistry course at UFSCar have about chemical concepts. A lot of incoherence was observed in student's mental models, which is an evidence that there are problems in the learning of chemistry education.

Hidróxido de níquel suportado em carbono: um catalisador de baixo custo para a eletro-oxidação de alcoóis em meio alcalino

The present manuscript shows the synthesis of nickel hydroxide supported in carbon (Ni(OH)2/C) as a alternative material for catalytic alcohol oxidation in alkaline medium. The Ni(OH)2/C was synthesized in different percentage using a sonic bath. No current densities variation during successive cyclic voltammetry experiments was observed. The Ni(OH)2/C electrodes exhibit a potent and persistent electrocatalytic activity towards the oxidation of different alcohols. In addition, alcohols electooxidation occurs in less positive potential compared with noble metal catalyst.

Determinação de enxofre em amostras vegetais por oxidação via seca em meio alcalino com detecção espectrofométrica

The sulphur take an essential role in plants and it is one of the main nutrients in several metabolic processes. The dry ash oxidation, using alkaline oxidizers agent, is the simplest and most economical form for the oxidation of Organic S to sulfate in plants. The objective of this work is to propose a method for sulfur determination in plants samples using dry ash oxidation and agent oxidizers alkaline. The quantification of S-SO4(2-) in samples was accomplished by turbidimetric method. The results demonstrated that the proposed method for oxidation alkaline was appropriate.

Aumento da resposta analítica por meio da otimização do sistema de injeção sem divisão de fluxo em cromatografia gasosa empregando a lei dos gases ideais

This paper reports the development of an easy, fast and effective procedure for the verification of the ideal gas law in splitless injection systems in order to improve the response. Results of a group of pesticides were used to demonstrate the suitability of the approach. The procedure helps establish experimental parameters through theoretical aspects. The improved instrumental response allowed extraction with lower sample volumes, the minimization of time and costs and the simplification of sample preparation.

Modelagem termodinâmica por extração por solvente de metais divalentes em meio sulfato usando D2EHPA

The extraction of divalent metals (Mn2+, Ni2+, Co2+ and Cu2+) in the system MSO4 - H2SO4 - H2O - D2EHPA in isoparaffin (17/21) was studied by a thermodynamic model based on chemical equilibria with mass and charge balance equations. The activity coefficients of all solutes in the aqueous phase were calculated by Davies equation. By applying this model, the equilibrium concentrations of solutes were calculated from de concentration of divalent metals and pH. The predicted distribution coefficients for the divalents metals were in good agreement with experimental results.

Dinâmica oscilatória em sistemas contendo bromato e 1,4-ciclo-hexanodiona em meio ácido: I. Efeito da temperatura

We present in this work the influence of temperature on the dynamics of homogeneous chemical systems containing bromate and 1,4-cyclohexanedione (1,4-CHD) in acidic media. In particular, the following systems were studied: bromate/1,4-CHD/acid, bromate/1,4-CHD/ferroin/acid and bromate/1,4-CHD/trisbipyridine ruthenium/acid. Investigations were carried out by means of an electrochemical probe, at five temperatures between 5 and 45 °C. Activation energies (Ea) were estimated in different ways for the pre-oscillatory and oscillatory regimes. In any case, the Ea was found to depend on the catalyst, composition and initial concentrations. In addition, it was observed that ferroin and trisbipyridine ruthenium act as catalysts only during the transition between the induction period and oscillatory regime.

Determinação dos parâmetros cinéticos e termodinâmicos da adsorção de L-cisteína em ouro por meio da técnica de microbalança a cristal de quartzo

This article discusses the adsorption kinetics of a L-cysteine monolayer onto a gold surface by means of information obtained through the QCM technique. The results indicate that the adsorption process is rapid and follows the Langmuir isotherm, in which adsorption and desorption are considered. From these measurements the following parameter values were obtained: k d = (4.2 ± 0.4) x 10-3 s-1, k a = 75 ± 6 M-1 s-1, Keq=(1.8 ± 0.3) x 10(4) M-1 and ΔGads = - (5.8 ± 0.2) kcal mol-1.

Glicerólise de óleo de peixe catalisada por lipase comercial de Rhizomucor miehei em meio com surfactante de grau alimentício

Omega-3 enriched partial acylglycerols are beneficial for human health. The aim of this study was to obtain monoacylglycerols (MAG) and diacylglycerols (DAG) by means of glycerolysis of fish oil catalyzed by a lipase from Rhizomucor miehei in the presence of food grade surfactants (Tween 65, 80 or 85). Glycerolysis was successful in the reaction media for all the tested surfactants, showing their potential for use as additives in such a system. The best results, however, were obtained for the reaction medium in the absence of surfactant whose peroxide value was the lowest after glycerolysis.

Preparação de derivados do lapachol em meio ácido e em meio básico: uma proposta de experimentos para a disciplina de Química Orgânica Experimental

In this educational paper we describe the extraction of lapachol from its natural source according to acid-base concepts in organic chemistry and the use of its derivatives β-lapachone and hydroxy-hydrolapachol to exemplify intramolecular cyclization, carbocation stability, Michael addition reaction and chromatography. The experiments were performed during three different undergraduate organic chemistry laboratory classes using low cost material, while avoiding color reagents for TLC visualization, as well as small-scale column chromatography to isolate the mixture of lapachol and β-lapachone.

Patenteamento em nanotecnologia no Brasil: desenvolvimento, potencialidades e reflexões para o meio ambiente e a saúde humana

Nanotechnology developments continue to be produced at exponential rates for a wide and diverse range of applications. In this paper was done a study of technological forecasting in nanotechnology applied to health, based on information drawn in Brazil from 1991 to 2010. The longitudinal evolutions of the number of patent applications, their topics, and their respective patent families have been evaluated for the total global activity. There were obtained 1352 patent applications in this period. It were analyzed the legal nature of the depositors, the year of deposit, depositors' home countries and processes. It has been a goal subsidizes the policy-makers to adapt and modernize the regulatory framework on nanotechnology and risks involving health as a strategic area in the politics of Science.

Influência do método de preparação de eletrocatalisadores PtRu/C sobre a atividade catalítica frente à reação de oxidação de etanol em meio ácido

In this work the influence of variations in the borohydrate reduction method on the properties of PtRu/C electrocatalysts was investigated. The electrocatalysts were prepared using 1:1 ; 2:1; 5:1; 50:1 and 250:1 molar ratios of NaBH4 to metals. The reduction was also performed by dripping or by fast addition of the solution. The results showed that PtRu nanoparticles obtained by fast addition had the smallest crystallite sizes. It was also noted that the catalytic activity increased as the borohydrate:metal molar ratio increased. The PtRu/C electrocatalyst (50:1) obtained by fast addition presented the best catalytic activity for ethanol electro-oxidation.