Resumo em Inglês:

The influence of glycerol and ornithine feeding on clavulanic acid (CA) production by Streptomyces clavuligerus was investigated. In batch experiments, CA maximum concentration (Cp max) ranged randomly from 430 to 560 mg.L-1, with a maximum increase of 10% in relation to the control run, without ornithine. However, the maximum volumetric productivity of CA (Pp max) of 13.7 mg.L-1.h-1 was obtained with 0.66 g.L-1 of ornithine, 44.2% higher than the Pp max in the control run. In fed-batch experiments, Cp max varied within the narrow range from 1.254 to 1.405 g.L-1, 2.5 times higher than that obtained in the control run. The presence of ornithine increased the Pp max, although it influenced only slightly the Cp max. Concerning glycerol, the highest CA production of 1.6 g.L-1 was obtained in the fed-batch with glycerol and ornithine (180 and 3.7 g.L−1) in a 10-L bioreactor, showing a positive effect of ornithine and glycerol, in the proper proportion (48.6:1), on CA biosynthesis.

Resumo em Inglês:

Enzymes have been extensively used in organic solvents to catalyze a variety of reactions of biological and industrial significance. In this work, the characteristics of free and immobilized inulinase were investigated in buffered solutions of butyl acetate. The influences of the organic solvent content on the optimal temperature and pH, the stabilities to temperature and pH and the kinetic parameters were systematically evaluated. The results showed that the organic solvent content had no effect on the optimal pH, either in the free or immobilized inulinase. For the immobilized enzyme, the optimal temperatures ranged from 55ºC to 60ºC, depending on the content of butyl acetate. At higher butyl acetate content, the stability of the immobilized enzyme increased for both pH and temperature. The organic solvent showed the tendency to increase the values of the kinetic parameters Km and v max for both free and immobilized inulinase.

Resumo em Inglês:

Under fed-batch process conditions, the statistical analysis of trace elements was performed by application of Plackett-Burman design (for screening tests) and response surface methodology (for predicting the optimal points) to achieve the highest level of canthaxanthin production from Dietzia natronolimnaea HS-1. Plackett-Burman design was conducted on eleven trace elements (i. e., aluminum, boron, cobalt, copper, iron, magnesium, manganese, molybdenum, selenium, vanadium and zinc) to select out elements that significantly enhance the canthaxanthin production of D. natronolimnaea HS-1. Plackett-Burman design revealed that Fe3+, Cu2+ and Zn2+ ions had the highest effect on canthaxanthin production of D. natronolimnaea HS-1 (P<0.05). These three elements were used for further optimization. By means of response surface methodology for the fed-batch process, the optimum conditions to achieve the highest level of canthaxanthin (8923±18 µg/L) were determined as follow: Fe3+ 30 ppm, Cu2+ 28.75 ppm and Zn2+ 27 ppm.

Resumo em Inglês:

This study presents the results of a mature landfill leachate treated by a homogeneous catalytic ozonation process with ions Fe2+ and Fe3+ at acidic pH. Quality assessments were performed using Taguchi's method (L8 design). Strong synergism was observed statistically between molecular ozone and ferric ions, pointing to their catalytic effect on •OH generation. The achievement of better organic matter depollution rates requires an ozone flow of 5 L h-1 (590 mg h-1 O3) and a ferric ion concentration of 5 mg L-1.

Resumo em Inglês:

An anaerobic fluidized bed reactor was used to assess the degradation of the surfactant linear alkylbenzene sulfonate (LAS). The reactor was inoculated with sludge from an UASB reactor treating swine wastewater and was fed with a synthetic substrate supplemented with LAS. Sand was used as support material for biomass immobilization. The reactor was kept in a controlled temperature chamber (30±1 ºC) and operated with a hydraulic retention time (HRT) of 18 h. The LAS concentration was gradually increased from 8.2±1.3 to 45.8±5.4 mg.L-1. The COD removal was 91%, on average, when the influent COD was 645±49 mg.L-1. The results obtained by chromatographic analysis showed that the reactor removed 93% of the LAS after 270 days of operation.

Resumo em Inglês:

Systematic ozonation tests were conducted by means of a mobile pilot plant. Water source 1 was a low turbidity stream with very low solids content and very low turbidity, apparent color and alkalinity. Water source 2 was reservoir water with higher turbidity, solids content and alkalinity than source 1. The ozone plant was a counter-current contactor composed of four columns in series. Variations in contact time, in the feed gas concentration (in terms of percent by weight of ozone) and in splitting of the total applied ozone dosage between columns 1 and 2 were tested. Concentration - time (CT) products were calculated and decay coefficients K were estimated from experimental data. The relative importance of water quality and certain operational parameters with regard to CT products and ozone decay was assessed. Total CT values seemed to increase with: (a) total applied ozone dosage, (b) percent by weight of ozone in the feed gas to the bubble contactor, (c) increasing contact time and (d) higher water quality, with regard to turbidity, apparent color, total organic carbon and particle counts. As the total applied ozone dosage was increased, the more important the contact time and ozone dosage configuration became for the total CT value. The apparent first order ozone decay rate constant (K) decreased with increasing total applied ozone dosage. The contact time appeared to exert a much stronger influence on total CT values than on K values, particularly so as the total applied ozone dosage was increased.

Resumo em Inglês:

The experiments and analyses performed included measurements of the physical properties of TiO2 powder such as the particle size, density, and consolidation. Experiments with nanometric TiO2powder of 204 nm average diameter show that, during consolidation, the adhesion of particles under normal stress is principally due to the van der Waals force for particle radii less than 300nm and the application of external force has no effect on the cohesion of the primary particles within this range; for particle radii around 300nm to 1.0µm the cohesion of the powder system is due to plastic deformation and the application of external force change the cohesion force to a plastic deformation between the agglomerates formed under these forces. This can be observed in the arrangement of the primary particles into dispersed agglomerates with sizes greater than the individual particles. The results obtained with the nanometric TiO2 powders show a more complex behavior than the micronic powders. This behavior is related to the structure of the nanometric particles in the packed bed; the evolution of this structure is made up of individualized and spherical agglomerate shapes. It has been experimentally observed that the powder structure is not perturbed by stresses of low intensities. A development of the different forces involved in interparticle contacts is outlined. The description of these forces involved in particle cohesion will help to understand the powder cohesion under consolidation.

Resumo em Inglês:

The study of non-Newtonian flow in plate heat exchangers (PHEs) is of great importance for the food industry. The objective of this work was to study the pressure drop of pineapple juice in a PHE with 50º chevron plates. Density and flow properties of pineapple juice were determined and correlated with temperature (17.4 < T < 85.8ºC) and soluble solids content (11.0 < Xs < 52.4 ºBrix). The Ostwald-de Waele (power law) model described well the rheological behavior. The friction factor for non-isothermal flow of pineapple juice in the PHE was obtained for diagonal and parallel/side flow. Experimental results were well correlated with the generalized Reynolds number (20 < Re g < 1230) and were compared with predictions from equations from the literature. The mean absolute error for pressure drop prediction was 4% for the diagonal plate and 10% for the parallel plate.

Resumo em Inglês:

The gas-liquid two-phase mass transfer process in microchannels is complicated due to the special dynamical characteristics. In this work, a novel method was explored to measure the liquid side volumetric mass transfer coefficient kLa. Pressure transducers were utilized to measure the pressure variation of upward gas-liquid two-phase flow in three vertical rectangular microchannels and the liquid side volumetric mass transfer coefficient kLa was calculated through the Pressure-Volume-Temperature correlation of the gas phase. Carbon dioxide-water, carbon dioxide-ethanol and carbon dioxide-n-propanol were used as working fluids, respectively. The dimensions of the microchannels were 40 µm×240 µm (depth×width), 100 µm×800 µm and 100 µm×2000 µm, respectively. Results showed that the channel diameter and the capillary number influence kLa remarkably and that the maximum value of kLa occurs in the annular flow regime. A new correlation of kLa was proposed based on the Sherwood number, Schmidt number and the capillary number. The predicted values of kLa agreed well with the experimental data.

Resumo em Inglês:

A simple and non-conventional electrospinning technique was employed for producing highly oriented Polyacrylonitrile (PAN) nanofibers. The PAN nanofibers were electrospun from 14 wt% solution of PAN in dimethylformamid (DMF) at 11 kv on a rotating drum with various linear speeds from 22.5 m/min to 67.7 m/min. The influence of take up velocity was investigated on the degree of alignment, internal structure and mechanical properties of collected PAN nanofibers. Using an image processing technique, the best degree of alignment was obtained for those nanofibers collected at a take up velocity of 59.5 m/min. Moreover, Raman spectroscopy was used for measuring molecular orientation of PAN nanofibers. Similarly, a maximum chain orientation parameter of 0.25 was determined for nanofibers collected at a take up velocity of 59.5 m/min.

Resumo em Inglês:

This work describes the calibration of a gas chromatograph equipped with a sulfur chemiluminescent detector with dual plasma (GC-SCD-DP) for analysis of sulfur-containing petroleum refinery gaseous streams. A packed column in an inert tube (Sulfinert) and an inlet system resistant to reactive sulfur compounds were used. The behavior of the calibration procedure over time depended on the sulfur compound: hydrogen sulfide (H2S), carbonyl sulfide (COS), methanethiol (MeSH) and dimethylsulfide (DMS) gave constant responses, whereas SO2 presented a systematic increase and dimethyldisulfide (DMDS) showed a systematic decrease of their response factors. In all cases, the response factors were lower than the ones found in the ASTM D 5504-08 method. The GC-SCD-DP technique proved to be a suitable tool for quantification of sulfur compounds (including SO2) at µg.m-3 levels in several petroleum refinery gaseous streams.

Resumo em Inglês:

Sulfated zirconia (SZ) is a widely used catalyst, which is synthesized by a solvent free method and the synthesized catalyst has been characterized. Neem Methyl Ester (Biodiesel) was prepared by a two-step process of esterification and transesterification from Neem oil with methanol in the presence of catalyst. Acid catalyst was used for the esterification and alkali catalyst (KOH) for the transesterification reaction. Optimal Free Fatty Acid (FFA) conversion was achieved using 1 wt% SZ as an acid catalyst with a methanol-to-oil molar ratio of 9:1, temperature of 65ºC and reaction time of 2 h. The acid value was reduced to 94% of the raw oil (24.76 mg KOH/g), which confirmed the conversion. Consequently, this pretreatment reduces the overall complexity of the process and a conversion efficiency of 95% is achieved when pretreated oil reacts with methanol in the presence of KOH.

Resumo em Inglês:

Pervaporation-assisted esterification of oleic acid and ethanol was investigated by means of heterogeneous acid catalysis with the aim of increasing the ethyl oleate yield. The experimental strategy comprised kinetic tests with Amberlyst 15 Wet (Rohm & Haas), the characterization of hydrophilic Pervap 1000 membrane (Sulzer) and the evaluation of the membrane-assisted reactor. Kinetic tests were carried out to study the effect of temperature, catalyst loading and ethanol/organic acid molar ratio for the esterification of oleic acid and ethanol. The ester yield and initial reaction rate were used as response. The hydrophilic poly(vinyl alcohol) membrane was able to remove water from the reaction medium and, hence, the ester yield was increased. The potential of coupling esterification and pervaporation was demonstrated, with a two-fold increase in the reaction yield of ethyl oleate.

Resumo em Inglês:

The substrate heating method was used to grow zeolite 4A coatings on copper plates. The reaction mixture was kept at 25º C, while the plate was heated to a higher temperature. In some of the synthesis experiments performed, the reaction mixture was circulated in the system. The coatings prepared were characterized by X-ray diffraction and scanning electron microscopy. It was demonstrated that crystalline and pure zeolite 4A coatings could be formed on copper by using the substrate heating method from a highly alkaline solution, in which dissolution and oxidation of the copper plates took place. A coating with about 310 µm mass equivalent thickness could be grown on copper after 72 h of synthesis. The thickness decreased when circulation was applied. Compared to coatings previously prepared on stainless steel plates under similar experimental conditions, thicker coatings were grown on copper. It is possible that the roughened surface of copper in the highly alkaline reaction mixture provided a higher number of nucleation sites.

Resumo em Inglês:

A sensor placement approach for the purpose of accurately estimating unknown parameters of a distributed parameter system is discussed. The idea is to convert the sensor location problem to a classical experimental design. The technique consists of analysing the extrema values of the sensitivity coefficients derived from the system and their corresponding spatial positions. This information is used to formulate an efficient computational optimum experiment design on discrete domains. The scheme studied is verified by a numerical example regarding the chemical reaction in a tubular reactor for two possible scenarios; stable and unstable operation conditions. The resulting approach is easy to implement and good estimates for the parameters of the system are obtained. This study shows that the measurement location plays an essential role in the parameter estimation procedure.

Resumo em Inglês:

Biocides play an important role in the preservation of a variety of products susceptible to microbiological growth such as paint, a material that can undergo microbial deterioration both in storing (inside the can) and after the application on a surface. In this work, artificial neural networks were used to predict the level of fungal growth on surfaces painted with water-based paints with biocide formulations containing different concentrations of ten kinds of commercial and experimental chemical agents. The use of neural networks is well known in chemical processes and they are a powerful tool for discovering relationships between sets of data. Industrial Environmental Tropical Chamber tests were used as the network training set. The importance of the each additive of the dry-film biocide formulation in prevention of biodeterioration was also examined.

Resumo em Inglês:

The problem of flow of a viscous incompressible gas with dust particles across an isothermal cylinder is discussed. The dust particles are assumed to be uniformly distributed throughout the gas. The equations of motion are simplified by writing the equations in dimensionless form and then solved numerically to describe the flow for different values of the physical parameters of interest. These parameters are the particle concentration parameter (R), the temperature relaxation time parameter (A) and the particle mass parameter (G). Many results are obtained and a representative set is displayed in graphs and tables. It is found that a distinct decrease in the velocity function is observed with an increase in the particle concentration parameter and increasing particle mass parameter induces a reduction in velocity. Furthermore, comparisons with previously published work are performed and the results are found to be in excellent agreement.

Resumo em Inglês:

A numerical investigation of laminar flow in a two-dimensional, Cartesian flow that exits from a short channel with a backward-facing step is carried out in this work for the Reynolds number range of 0.00054 < Re < 54. We studied the steady state fluid dynamics, phase change and heat transfer of the flow. We analyzed the flow behavior occurring for different outflow velocities and three different configuration of the step. The incompressible working fluid was glass. The temperature, streamline, phase change and pressure fields are obtained and analyzed as a function of position. In order to obtain a better understanding of the step angle influence on the fluid dynamics, we obtained the heat transfer flux rates and the axial velocity profiles.

Resumo em Inglês:

Filtration through membranes is a process largely employed in the food and chemical industry to separate particles. Sieves present some advantages in relation to conventional membranes such as high homogeneity in the pore sizes, smooth surfaces, straight-through pores, etc. In this paper we compare the selectivity in the exclusion of particles by size of sieves with circular and slit pores with the same porosity. The selectivity was investigated by filtering a mixture of rutin in water in a cross-flow filtration system. The particle-size distribution of the rutin solution was measured before and after microfiltration. The results showed a high efficiency in the size exclusion of particles for microsieves with circular pores. The filtration through a commercial membrane (net filter) with similar characteristics was also characterized for comparison.

Resumo em Inglês:

In this work, the recovery of base oils from waste lubricants following the steps of solvent extraction, adsorption on solids and solvent removal by evaporation was evaluated. In the step of solvent extraction, the most efficient was 1-butanol, followed by tert-butanol, 2-propanol and ethanol; for the step of adsorption, activated carbon was the most effective solid for PAH removal, confirming the similarity of these compounds with petroleum aromatic fractions. Thus, the optimum solvent-adsorbent pair for the recovery of used lubricant oils through the proposed methodology was 1-butanol/activated carbon. At the end of the process, it was possible to establish a set of steps that permit the recovery of lubricant base oils with lower content of contaminants.