Resumo em Inglês:

Endo-and exo-polygalacturonase (PG) production by Aspergillus oryzae IPT 301 was evaluated in a batch bioreactor in media containing 0, 10, and 20 g.L-1 pectin and 0 to 30 g.L-1 glucose. For cultivations in which the pH was not controlled, the use of 20 g.L-1 pectin and 10 g.L-1 glucose resulted in superior enzyme activities compared to control media with 0 and 10 g.L-1 of the inducer and the same glucose concentration. Maximum endo-PG and exo-PG activities were 125.0 and 76.3 U.mL-1, respectively. For cultivations in which the pH was controlled to a minimum value of 2.7, media containing 20 g.L-1 pectin and 20 to 50 g.L-1 glucose were tested and significant improvement of both activities was attained. Maximum enzyme activities (175.0 U.mL-1 for endo-PG and 103.0 U.mL-1 for exo-PG) were obtained in pH-controlled batch experiments with 30 g.L-1 glucose.

Resumo em Inglês:

The nutritional medium compositions required for chitosanase production by Streptomyces albus YT2 were optimized, and the strain was isolated from the coastal soil of Bohai Sea. Plackett-Burman design was applied to evaluate the effect of different medium compositions obtained by one-factor-at-a-time experiments. Glucose, peptone and MgSO4 were found to influence the activity of chitosanase significantly. The steepest ascent method was employed to approach the experimental design space, followed by the use of Box-Behnken design and response surface methodology for further optimization of the chitosanase production. The medium composition for optimal production of chitosanase was as follows: 0.5 g/L chitosan, 55 g/L glucose, 1 g/L peptone, 2 g/L (NH4)2SO4, 8 g/L urea, 1 g/L NH4Cl, 3 g/L KH2PO4, 1 g/L FeSO4·7H2O, 2 g/L ZnSO4·7H2O, 2 g/L CaCl2·6H2O, 2 g/L MnSO4·H2O and 2 g/L NaCl. The chitosanase production was found to increase from 11.56 U/mL to 39.87 U/mL, a 3.47-fold increase compared with that using the original medium.

Resumo em Inglês:

Experiments were carried out on the preparation and characterization of dispersions of sand in ethylene glycol-water (50-50%) mixture. The dispersions were prepared by stirred bead milling of 20-30 µm sand (in water) followed by dilution with water and ethylene glycol. The influence of temperature (31-45 ºC), particle concentration (< 2 vol %) and ultrasonication on the viscosity of sand-ethylene glycol-water dispersions was studied. The thermal conductivity of dispersions as a function of particle concentration and ultrasonication has also been investigated. Correlations were developed for the prediction of relative viscosity and thermal conductivity ratio of the dispersions. Our results indicate that the sand-ethylene glycol-water dispersions, prepared by stirred bead milling and ultrasonication, have potential as coolants.

Resumo em Inglês:

Particulate fouling studies of a hydrocarbon based suspension containing 2 µm alumina particles were performed in an annular heat exchanger having a hydraulic diameter of 14.7 mm. During fouling experiments, the classical asymptotical behavior was observed. It is shown that particle concentration, fluid velocity, and wall temperature have strong influences on the fouling curve and the asymptotic fouling resistance. Furthermore, a mathematical model is developed to formulate the asymptotic fouling resistance in terms of the mass transfer coefficient, thermophoresis velocity, and fluid shear rate. The results demonstrate that the prediction of the new model is in good agreement with the experimental observations.

Resumo em Inglês:

Study of liquid behavior in an expanded bed adsorption (EBA) system is important for understanding, modeling and predicting nanobioproduct/biomolecule adsorption performance in such processes. In this work, in order to analyze the local axial dispersion parameters, simple custom NBG (Nano Biotechnology Group) expanded bed columns with 10 and 26 mm inner diameter were modified by insertion of sampling holes. Based on this configuration, the particles and liquid can be withdrawn directly from various axial positions of the columns. Streamline DEAE particles were used as solid phase in this work. The effects of factors such as liquid velocity, viscosity, settled bed height and column diameter on the hydrodynamic parameters were investigated. Local bed voidages in different axial bed positions were measured by a direct procedure within the column with 26 mm diameter. Increasing trend of voidage with velocity at a certain position of the bed and with bed height at a certain degree of expansion was observed. Residence time distribution (RTD) analysis at various bed points showed approximately uniform hydrodynamic behavior in the column with 10 mm diameter while a decreasing trend of mixing/dispersion along the bed height at a certain degree of expansion was seen in the column with 26 mm diameter. Also lower mixing/dispersion occured in the smaller diameter column. Finally, a combination of two empirical correlations proposed by Richardson-Zaki and Tong-Sun was successfully employed for identification of the bed voidage at various bed heights (RSSE=99.9%). Among the empirical correlations presented in the literatures for variation of the axial dispersion coefficient, the Yun correlation gave good agreement with our experimental data (RSSE=87%) in this column.

Resumo em Inglês:

The main objective of this study was to evaluate the effect of the drying process on the vitamin C levels and physical properties of dedo-de-moça pepper. The drying kinetics and the structural properties were determined as a function of moisture content. Convective drying was compared with freeze-drying in terms of product quality, structural properties, retention of vitamin C and rehydration characteristics. Empirical and semi-empirical equations were used to describe the drying and rehydration kinetics. Nonlinear analysis applied to results of convective drying, based on curvature measures and bias measures, showed that the only equation that gives good inference results based on least squares estimators is the Overhults equation. The characterization of the rehydration process was done by determining the indexes that take into account the water absorption capacity and solutes losses. The material dried by lyophilization show greater potential to rehydrate.

Resumo em Inglês:

This work describes the preparation of composites of polypropylene and organophilic bentonites based on Brazilian and Argentinean bentonites. During the processing of the samples in a twin screw microextruder, torque and pressures of the extruder were accompanied and the viscosity values were calculated. No significant changes in the torque, pressure and viscosity were found for composites prepared with different bentonites. The samples were characterized by XRD and TEM to evaluate the structure and dispersion of the organophilic bentonites. Composites with exfoliated, partially exfoliated and intercalated structures were obtained and correlations between the intrinsic properties of the sodium clays and organophilic bentonites and their influence on the composites were studied. The cation exchange capacity of the sodium bentonites and the swelling capacity of the organophilic bentonites were the most important properties to obtain exfoliated structures in composites. All bentonites showed the potential to obtain polymer nanocomposites, but the ones from Argentina displayed the best results.

Resumo em Inglês:

Industrial wastewater containing non-biodegradable organic pollutants consists of highly toxic effluents whose treatment is necessary due to environmental and economical restrictions. In order to treat these effluents, an electrochemical process using a dimensionally stable anode (DSA®) and boron-doped diamond (BDD) electrode was studied. The performance of these electrodes for COD removal from aqueous phenol solution was evaluated in the absence and presence of different chloride concentrations. The results showed that DSA®could be successfully used to remove COD when high chloride concentration (3035 mg L-1 Cl-) and mild current density are employed (50 mA cm-2). On the other hand, the presence of chloride did not have the same significant effect on the COD depletion rate using BDD; however, under mild conditions (50 mA cm-2, 0.190 m s-1), the addition of 607 mg L-1 Cl- improved the COD removal by approximately 52% after 8 hours of electrolysis. The effect of current density (i) and flow velocity (v) were also studied, and it was verified that they have an important role on the process performance, especially when DSA® is used.

Resumo em Inglês:

The antibacterial activity of MgO nanoparticles prepared by a sonication method was evaluated in this paper. The effect of calcination conditions on the size and antibacterial activity of MgO nanoparticles was investigated. MgO nanoparticles were characterized for purity (TGA), crystallinity and crystal size (XRD), particle size and morphology (TEM) and surface area (BET). Results showed that the smallest size of 6 nm could be obtained. The lethal effects of nanocrystalline MgO were evaluated on Lactobacillus plantarum. At a concentration of 100 ppm, the killing effect of MgO was close to 1 log reduction for L. plantarum after 24 h exposure. At 1000 ppm and 24 h exposure, the killing effect of MgO was more than a 2.8 log reduction. With the increase of calcination time, the lethal effect of MgO nanoparticles increased after 6 h or 24 h exposure at 100 ppm or 1000 ppm. 2.86 log and 2.89 log were killed at 1000 ppm after 24 h exposure using the sample MgO, sonication, A, and the sample MgO, sonication, B, respectively. When the sample MgO, sonication, C, was used, the lethal quantity of L. plantarum was increased to a 3.36 log reduction.

Resumo em Inglês:

Nano-assisted inclusion separation of alkali metals from basic solutions was reported by an inclusion-facilitated emulsion liquid membrane process. The novelty of this study is application of nanobaskets of calixcrown in the selective and efficient separation of alkali metals as both the carrier and the surfactant. For this purpose, two diacids, p-tert-butylcalix[4]arene-1,2-crown-3 in the cone and the 1,2alternate conformation, as well as another diacid, p-tert-butylcalix[4]arene-1,2-thiacrown-3 in the cone conformation, were synthesized. Their inclusion-extraction parameters were optimized, including the calixcrown scaffold (04, 4 wt%) as the carrier/demulsifier, commercial kerosene as the diluent in the membrane, sulphonic acid (0.2 M) and ammonium carbonate (0.4 M) as the strip and the feed phases; the phase and the treat ratios were 0.8 and 0.3, mixing speed (300 rpm), and initial solute concentration (100 mg/L). The selectivity of the membrane was examined for more than ten interfering cations was examined and the results reveled that, under the optimized operating condition, the degree of inclusion-extraction of alkali metals was as high as 98-99%.

Resumo em Inglês:

CO(15NH2)2 enriched with the stable isotope 15N was synthesized based on a reaction involving CO, 15NH3, and S in the presence of CH3OH. The method differs from the industrial method; a stainless steel reactor internally lined with polytetrafluoroethylene (PTFE) was used in a discontinuous process under low pressure and temperature. The yield of the synthesis was evaluated as a function of the parameters: the amount of reagents, reaction time, addition of H2S, liquid solution and reaction temperature. The results showed that under optimum conditions (1.36, 4.01, and 4.48 g of 15NH3, CO, and S, respectively, 40 ml CH3OH, 40 mg H2S, 100 ºC and 120 min of reaction) 1.82 g (yield 76.5%) of the compound was obtained per batch. The synthesized CO(15NH2)2 contained 46.2% N, 0.55% biuret, melting point of 132.55 ºC and did not exhibit isotopic fractionation. The production cost of CO(15NH2)2 with 90.0 at. % 15N was US$ 238.60 per gram.

Resumo em Inglês:

This work studies the optimization and control of a styrene polymerization reactor. The proposed strategy deals with the case where, because of market conditions and equipment deterioration, the optimal operating point of the continuous reactor is modified significantly along the operation time and the control system has to search for this optimum point, besides keeping the reactor system stable at any possible point. The approach considered here consists of three layers: the Real Time Optimization (RTO), the Model Predictive Control (MPC) and a Target Calculation (TC) that coordinates the communication between the two other layers and guarantees the stability of the whole structure. The proposed algorithm is simulated with the phenomenological model of a styrene polymerization reactor, which has been widely used as a benchmark for process control. The complete optimization structure for the styrene process including disturbances rejection is developed. The simulation results show the robustness of the proposed strategy and the capability to deal with disturbances while the economic objective is optimized.

Resumo em Inglês:

CFD modeling for an internal loop airlift reactor is developed for different superficial gas velocities, ranging from 0.015 to 0.073 m/s. Based on the presence of gas bubbles in the downcomer, three regimes can be generally classified as: no gas bubbles (I), stagnation of gas bubbles (II), and recirculation of gas bubbles into the riser (III). The aim of the study is to carefully investigate the regime transition from II to III by considering the gas distribution. In regime II, the CFD simulation results show that the gas holdup difference between the riser and the downcomer remains constant. Due to the transition from regime II to III, the gas holdup difference sharply increases and the ratio of gas holdup in the downcomer and riser changes between the two regimes. At a superficial gas velocity slightly lower than that of the transitional regime, a small amount of gas is dragged to the riser, while the behavior of the regime is similar to regime II. The computational results show that CFD can be used as an effective tool to provide information on the details of the transition regime in internal loop airlift reactors.

Resumo em Inglês:

In Brazil, the species Maytenus aquifolia and Maytenus ilicifolia are widely used in popular medicine in the form of teas for stomach and ulcer illness treatment. Despite the great interest in Maytenus aquifolia therapeutic properties and the fact that it is an abundant and native plant growing in Brazil, there is a lack of information in the literature concerning the extraction at high pressures. In this context, this work is focused on the mathematical modelling of the packed-bed extraction of Maytenus aquifolia with compressed CO2. Three mathematical models were used to represent the experimental data. The experiments were performed in a laboratory-scale unit, evaluating the effects of temperature (293 to 323 K), pressure (100 to 250 bar), and extraction time on the yield of the extracts. Results show that the extraction temperature and solvent density exerted a pronounced effect on yield. The mathematical model of Sovová was the most suitable to represent the experimental extraction data of M. aquifolia.