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Brazilian Journal of Chemical Engineering, Volume: 25, Número: 2, Publicado: 2008
  • A kinetic model for growth and biosynthesis of medium-chain-length poly-(3-hydroxyalkanoates) in Pseudomonas putida Bioprocess Engineering

    Annuar, M. S. M.; Tan, I. K. P.; Ibrahim, S.; Ramachandran, K. B.

    Resumo em Inglês:

    A kinetic model is presented giving a mathematical description of batch culture of Pseudomonas putida PGA1 grown using saponified palm kernel oil as carbon source and ammonium as the limiting nutrient. The growth of the micro-organism is well-described using Tessier-type model which takes into account the inhibitory effect of ammonium at high concentrations. The ammonium consumption rate by the cells is related in proportion to the rate of growth. The intracellular production of medium-chain-length poly-(3-hydroxyalkanoates) (PHA MCL) by P. putida PGA1 cells is reasonably modeled by the modified Luedeking-Piret kinetics, which incorporate a function of product synthesis inhibition (or reduction) by ammonium above a threshold level.
  • Immobilization of starch phosphorylase from cabbage leaves: production of glucose-1-phosphate Bioprocess Engineering

    Garg, N.; Kumar, A.

    Resumo em Inglês:

    Starch phosphorylase has been isolated from cabbage (Elephantopus scabar) leaves and partially purified using ammonium sulfate fractionation. The partially purified enzyme was desalted using Sephadex-G-25 chromatography. In the direction of polysaccharide synthesis, the enzyme showed optimum activity at pH 6.0 with two half pH optima at pH 5.3 and pH 7.1 whereas in the direction of glucose-1-phosphate formation, it showed optimum pH at pH 7.0 with half pH-optima at pH 6.4 and 7.6. The optimum temperature for the enzyme activity has been found to be 37ºC with two half temperature optima at 34ºC and 40ºC. The partially purified enzyme has been immobilized using egg shell as solid support. The percentage retention of the enzyme on egg shell was nearly 56%. After immobilization, specific activity of the enzyme increased from 0. 0225 to 0.0452. Upon immobilization, there was a slight alkaline shift in the optimum pH when assayed in both the directions. The immobilized enzyme also displayed increased optimum temperature and thermo-stability and could be reused number of times. The increase in thermo-stability and reusability of the immobilized enzyme has been exploited for the production of glucose-1-phosphate, a cytostatic compound used in cardio-therapy. The glucose-1-phosphate produced has been purified with nearly 95% purity after adsorption chromatography on norite and ion exchange chromatography on DEAE cellulose.
  • Immobilisation of Bacillus subtilis NRC33a levansucrase and some studies on its properties Bioprocess Engineering

    Esawy, M. A.; Mahmoud, D. A. R.; Fattah, A. F. A.

    Resumo em Inglês:

    Bacillus subtilis NRC33a levansucrase was immobilised on different carriers using different immobilisation methods including physical adsorption, covalent binding, ionic binding and entrapment. The immobilised enzyme prepared by covalent binding on chitosan through 3% gluteraldehyde had the highest immobilization yield (81.51%). Therefore, it was used as a typical example for Bacillus subtilis NRC33a immobilised levansucrase and its properties were investigated. The time of the reaction and substrate concentration revealed that the activity of the immobilised enzyme was relatively lower than the free enzyme. The immobilised levansucrase showed a slight increase in activity compared with the free enzyme above 35°C. The activation energies were 6.62 and 9.27 kcal mol-1 for free and immobilised enzyme respectively. Although the thermal stability of the immobilised levansucrase was significantly improved in comparison to the free form, the deactivation energy of the immobilised enzyme was lower than that of the free enzyme. The half life of the immobilised and free levansucrase was also determined. The effect of different pH values reported that at acidic pH the activity of the immobilised levansucrase was higher than that of the free enzyme. The study of pH stability of free and immobilised levansucrase showed that the immobilisation process protected the enzyme from alkaline and severe acidic media. The effect of various metal ions showed that the free levansucrase was more sensitive to the inhibitory effect of the investigated substances. Immobilised levansucrase retained 51.13% after 14 repeated uses.
  • Effect of dissolved oxygen concentration on red pigment and citrinin production by Monascus purpureus ATCC 36928 Bioprocess Engineering

    Pereira, D. G.; Tonso, A.; Kilikian, B. V.

    Resumo em Inglês:

    The present study investigated the effects of agitation speed, N (200, 500, 600 or 700 rpm), and dissolved oxygen concentration, C (120, >70, 70, 60, 10 or < 10%), on red pigment and citrinin production by Monascus purpureus ATCC 36928, cultivated in liquid medium by a batch process. The gas flow rate was the same for all runs with C controlled by means of the incoming gas composition control (air/N2 or air/O2). From the response surface plots it can be verified that the effect of C was greater than that of N on the production of both metabolites. The absorbance for red pigments varied from 1.6 U (C< 10%; N=200 rpm) up to 3.3 U (C=60%; N=600 rpm), an increase of 106%, while citrinin concentration increased 257%, from 14.2 to 50.7 mg.L-1. The most appropriate conditions were C=60% and N=600rpm, under which the highest red pigment absorbance (3.3U) and half of the highest citrinin concentration were obtained.
  • Enhancement of solubility of albendazole by complexation with β-cyclodextrin Bioprocess Engineering

    Moriwaki, C.; Costa, G. L.; Ferracini, C. N.; Moraes, F. F. de; Zanin, G. M.; Pineda, E. A. G.; Matioli, G.

    Resumo em Inglês:

    A high dosage of albendazole (ABZ) is required for treating systemic helminthe infections because of its low solubility. Aiming at increasing ABZ solubility, complexation with beta-cyclodextrin (β-CD) using aqueous and acetic acid solutions as ABZ solubilizer was studied. In aqueous β-CD, complexation increased solubility 53.4 times, giving a complex equilibrium constant of 1266 L mol-1 with a maximum ABZ concentration of 276 µmol L-1 for 16.3 mmol L-1 β-CD. For complexation in 1.05 mol L-1 acetic acid, UV absorbance spectra and ¹H-NMR analysis confirmed complex formation. The UV absorbance of ABZ/acid acetic/β-CD solutions was modeled by the formation of two complexes with molar ratios 1:1 and 1:2 ABZ:β-CD. When neutralized with NaOH these solutions did not form precipitates only for the ABZ:β-CD molar ratios of 1:8 and 1:10, showing that ABZ solubility could be increased 306 times. Results show that high β-CD molar ratios hold ABZ in solution by complexation enhanced by the acetate anion.
  • Use of weathered diesel oil as a low-cost raw material for biosurfactant production Bioprocess Engineering

    Mariano, A. P.; Bonotto, D. M.; Angelis, D. F.; Pirôllo, M. P. S.; Contiero, J.

    Resumo em Inglês:

    This work aimed to investigate the capability of biosurfactant production by Staphylococcus hominis, Kocuria palustris and Pseudomonas aeruginosa LBI, using weathered diesel oil from a long-standing spillage as raw material. The effect of the culture media (Robert or Bushnell-Haas) and of the carbon source (spilled diesel oil or commercial diesel oil) on biosurfactant production was evaluated. Erlenmeyer flasks (250 mL) containing the cell broth were agitated (240 rpm) for 144 h at 27±2ºC. Biosurfactant production was monitored according to the De Nöuy ring method using a Krüss K6 tensiometer. Considering the possibility of intracellular storage of biosurfactant in the cell wall of the cultures S. hominis and K. palustris, experiments were also done applying ultrasound as a way to rupture the cells. For the conditions studied, the cultures did not indicate production of biosurfactants. Results obtained with a hydrocarbon biodegradability test based on the redox indicator 2,6-dichlorophenol indophenol showed that only the commercial diesel was biodegraded by the cultures.
  • Effect of ammonia load on efficiency of nitrogen removal in an SBBR with liquid-phase circulation Environmental Engineering

    Canto, C. S. A.; Ratusznei, S. M.; Rodrigues, J. A. D.; Zaiat, M.; Foresti, E.

    Resumo em Inglês:

    The removal of biological nitrogen from a synthetic wastewater with different ammonium nitrogen concentrations (50 and 100 mgN-NH4+/L) by a nitrification and denitrification process using a sequencing batch biofilm reactor (SBBR) with liquid-phase circulation was studied. The system with a total working volume of 4.6 L (3.7 L in the reactor and 0.9 L in the reservoir) treated 2.1 L of synthetic wastewater in 12-h cycles. As inoculum two types of biomass were used: an anaerobic/anoxic one from an up-flow anaerobic sludge blanket reactor (UASB) and an aerobic one from a prolonged aeration activated sludge system. The system, maintained at 30 ± 1 ºC, operated in batch mode followed by fed-batch mode and was aerated intermittently. During fed-batch operation the reactor was fed with an external carbon source as electron donor in the denitrifying step and with no aeration. When the reactor was fed with 50 mgN-NH4+/L, efficiencies of removal of ammonium nitrogen and total nitrogen from the effluent were 93.8 and 72.2%, respectively, and nitrite, nitrate and organic nitrogen concentrations were 0.07, 6.4 and 0.5 mg/L, respectively. On the other hand, when the influent ammonium nitrogen concentration was 100 mgN-NH4+/L, residual nitrite and nitrate were 0.17 and 20.4, respectively, and no N-Org was found in the effluent. It should be mentioned that residual nitrate remained unaltered at the different C/N ratios used. Consequently, efficiency of total nitrogen removal was reduced to 66.7%, despite efficiency of ammonium nitrogen removal exceeding 90%. These results show the potential of the proposed system in removing ammonium nitrogen from liquid effluents with a moderate ammonium nitrogen concentration.
  • Effect of mixing mode on the behavior of an ASBBR with immobilized biomass in the treatment of cheese whey Fluid Dynamics, Heat And Mass Transfer And Other Topics

    Damasceno, L. H. S.; Rodrigues, José A. D.; Ratusznei, S. M.; Zaiat, M.; Foresti, E.

    Resumo em Inglês:

    A hydrodynamic study of a mechanically stirred anaerobic sequencing batch biofilm reactor (ASBBR) containing immobilized biomass on polyurethane foam was performed with the aim to determine homogeneity of the reactor based on total mixing time. Turbine or helix propellers were used for stirring at rotor speeds of 100, 200, 300 and 500 rpm. Experimental values obtained were fitted to a Boltzmann sigmoid. Homogenization times of the reactor were negligible when compared to the 8-h cycle time for all conditions studied. At low propeller rotations the turbine propeller showed the best performance. For higher rotations total mixing times were similar for both propellers; however the helix propeller had better homogeneity conditions. At a subsequent stage the system was operated in batch mode treating cheese whey at concentrations of 500, 1000 and 2000 mgCOD/L and rotations of 200, 300 and 500 rpm. In these assays the importance of the propeller became evident not only for mixing, but also for substrate flow across the bed containing immobilized biomass. Due to axial flow, the helix propeller offered better mass transfer conditions, evidenced by improved organic matter conversion and lower production of total volatile acids.
  • Mathematical modeling of handmade recycled paper drying kinetics and sorption isotherms Fluid Dynamics, Heat And Mass Transfer And Other Topics

    Vieira, M. G. A.; Rocha, S. C. S.

    Resumo em Inglês:

    The objective of this work is to analyze and compare the natural and forced convective drying of handmade recycled paper. Drying of recycled cellulose pulp was carried out under laboratory environment conditions and in a convective dryer with forced air circulation and controlled conditions of air temperature and velocity. The tests were conducted following a two-factor central composed factorial design of experiments, with six runs at the central point. The drying results were analyzed and fitted to mathematical models of Fick, Henderson and Pabis (Fick’s modified equation), Page and He (considering the nonlinear Fick effect). The model of Page represented best the experimental data and the one of Henderson and Pabis resulted in an adequate fit for the paper drying kinetics. Sorption isotherms were determined for the dried paper and the models of GAB (Guggenheim-Anderson-de Boer) and GDW (Generalised D’Arcy and Watt) resulted in excellent fits of the experimental data. The water sorption mechanism was suggested by the analysis of the calculated parameters of the GDW model.
  • Evaluation and optimization of non enzymatic browning of “cajuina” during thermal treatment Fluid Dynamics, Heat And Mass Transfer And Other Topics

    Damasceno, L. F.; Fernandes, F. A. N.; Magalhães, M. M. A.; Brito, E. S.

    Resumo em Inglês:

    "Cajuina" is a very popular drink in the Brazilian northeastern region and is produced by clarifying cashew apple juice. To preserve "cajuina" from chancing, the clarified cashew apple juice is submitted to thermal treatment where a desired final color should be obtained. To optimize color formation while maintaining high vitamin C and low 5-hydroxymethylfurfural (5-HMF) concentrations the thermal treatment of "cajuina" needs to be studied and the non enzymatic mechanism should be better understood and controlled. In this work the effect of thermal treatment on "cajuina" (clarified cashew apple juice) was studied at temperatures from 88°C to 121°C. Changes in color were measured and the variation in vitamin C, 5-hydroxymethylfurfural (5-HMF) and sugar content were used to evaluate non enzymatic browning. The kinetic models were used to optimize the thermal treatment to produce "cajuina" with an absorbance at 420 nm of 0.023.
  • Study on biodegradable aromatic/aliphatic copolyesters Kinetic And Catalysis, Reaction Engineering And Materials Science

    Chen, Yiwang; Tan, Licheng; Chen, Lie; Yang, Yan; Wang, Xiaofeng

    Resumo em Inglês:

    Progress on biodegradable aromatic/aliphatic copolyesters based on aliphatic and aromatic diacids, diols and ester monomers was reviewed. The aromatic/aliphatic copolyesters combined excellent mechanical properties with biodegradability. Physical properties and biodegradability of copolyesters varied with chain length of the aliphatic polyester segment and atacticity of copolyesters. The processability of copolyesters could be improved significantly after incorporating a stiff chain segment through copolymerization of aliphatic polyesters with an aromatic liquid crystal element. The aromatic/aliphatic copolyesters as a new type of biodegradable materials could replace some general plastics in certain applications, namely biomedical and environmental friendly fields.
  • Simulation of styrene polymerization reactors: kinetic and thermodynamic modeling Kinetic And Catalysis, Reaction Engineering And Materials Science

    Almeida, A. S.; Wada, K.; Secchi, A. R.

    Resumo em Inglês:

    A mathematical model for the free radical polymerization of styrene is developed to predict the steady-state and dynamic behavior of a continuous process. Special emphasis is given for the kinetic and thermodynamic models, where the most sensitive parameters were estimated using data from an industrial plant. The thermodynamic model is based on a cubic equation of state and a mixing rule applied to the low-pressure vapor-liquid equilibrium of polymeric solutions, suitable for modeling the auto-refrigerated polymerization reactors, which use the vaporization rate to remove the reaction heat from the exothermic reactions. The simulation results show the high predictive capability of the proposed model when compared with plant data for conversion, average molecular weights, polydispersity, melt flow index, and thermal properties for different polymer grades.
  • Deactivation properties of a high-productive vanadia-titania catalyst for oxidation of o-xylene to phthalic anhydride Kinetic And Catalysis, Reaction Engineering And Materials Science

    Georgieva, A. T.; Anastasov, A. I.; Nikolov, V. A.

    Resumo em Inglês:

    The behavior of a high-productive V2O5-TiO2 (anatase) supported O 4-28 catalyst for oxidation of o-xylene to phthalic anhydride was investigated in the first three years of its exploitation in industry. By using a suitable mathematical model, an identification problem was solved and activation profiles of the catalyst along a fixed bed located in the tubes of an industrial reactor were determined. Experimental temperature regimes and yields of the main and side products for different periods of the catalyst life were used. The proper technological regimes providing for a maximum yield according to the requirements of the catalyst producer company were defined.
  • Cellulose acetate-based molecularly imprinted polymeric membrane for separation of vanillin and o-vanillin Kinetic And Catalysis, Reaction Engineering And Materials Science

    Zhang, Chunjing; Zhong, Shian; Yang, Zhengpeng

    Resumo em Inglês:

    Cellulose acetate-based molecularly imprinted polymeric membranes were prepared using vanillin as template molecule. The microscopic structure of the resultant polymeric membranes was characterized by SEM and FTIR spectroscopy, and the selective binding properties and separation capacity of the membranes for vanillin and o-vanillin were tested with binding experiments and separate experiments, respectively. The results showed that the vanillin-imprinted polymeric membranes displayed higher binding and separation capacity for vanillin in comparison with the non-imprinted polymeric membranes; the maximum binding amount Qmax for vanillin is 387.3 µmol/g and the selectivity factor is 3.82 for vanillin/o-vanillin. In addition, the effect of cross-linker concentration on the binding of vanillin on the imprinted polymeric membranes was also evaluated and the optimal concentration is 320 mM.
  • Kinetics of barium sulphate reaction crystallization in crystallizers with internal circulation Kinetic And Catalysis, Reaction Engineering And Materials Science

    Koralewska, J.; Piotrowski, K.; Wierzbowska, B.; Matynia, A.

    Resumo em Inglês:

    Kinetic calculation results describing the observed nucleation and growth rates of barium sulphate crystals precipitated in an integrated reaction-crystallization process in a barium sulphate-ammonium chloride-water system are presented and analyzed. The scope of experiments included two continuous model DTM-type crystallizers (Draft Tube Magma) with internal circulation of the suspension forced by a liquid jet-pump device responsible for stable and intensive enough ascending/descending flow of BaSO4 crystal magma in a mixing chamber. For comparison purposes the experimental data corresponding to a continuous DT (Draft Tube) crystallizer with propeller agitator are presented and discussed. The various types of laboratory crystallizers used were fed with concentrated water solution of barium chloride (of 10 or 24 mass %) and - in a stoichiometric proportion - crystalline ammonium sulphate, assuming isothermal (348 K) and hydrodynamic (average residence time of suspension in a crystallizer: 900 s) process conditions. The observed nucleation and growth rates of barium sulphate crystals were estimated on the basis of crystal size distributions (CSDs) using convenient calculation scheme derived for an MSMPR (Mixed Suspension Mixed Product Removal) model approach. Considering the experimental population density distribution courses, a size-dependent growth (SDG) phenomenon was taken into account in the kinetic calculations. Five SDG kinetic models recommended in the accessible literature were used for kinetic parameter values estimation. It was proved statistically, that Rojkowski’s two SDG models (hyperbolic and exponential) best suit for our own experimental data description. The experimental data presented can be practically applied for improving the constructions of liquid jet-pump DTM crystallizers recommended for reaction crystallization of sparingly soluble inorganic salts (especially for high concentrations of reaction substrates) in the modern industrial-scale technologies.
  • Surface morphology of spray-dried nanoparticle-coated microparticles designed as an oral drug delivery system Kinetic And Catalysis, Reaction Engineering And Materials Science

    Beck, R. C. R.; Lionzo, M. I. Z.; Costa, T. M. H.; Benvenutti, E. V.; Ré, M. I.; Gallas, M. R.; Pohlmann, A. R.; Guterres, S. S.

    Resumo em Inglês:

    This paper was devoted to studying the influence of coating material (nanocapsules or nanospheres), drug model (diclofenac, acid or salt) and method of preparation on the morphological characteristics of nanoparticle-coated microparticles. The cores of microparticles were obtained by spray drying or evaporation and the coating was applied by spray drying. SEM analyses showed nanostructures coating the surface of nanocapsule-coated microparticles and a rugged surface for nanosphere-coated microparticles. The decrease in their surface areas was controlled by the nanoparticulated system, which was not dependent on microparticle size. Optical microscopy and X-ray analyses indicated that acid diclofenac crystals were present in formulations prepared with the acid as well as in the nanocapsule-coated microparticles prepared with the salt. The control of coating is dependent on the use of nanocapsules or nanospheres and independent of either the characteristics of the drug or the method of preparing the core.
  • Comparison of techniques for the determination of conversion during suspension polymerization reactions Kinetic And Catalysis, Reaction Engineering And Materials Science

    Santos, J. C.; Lopes, C. N.; Reis, M. M.; Giudici, R.; Sayer, C.; Machado, R. A. F.; Araújo, P. H. H.

    Resumo em Inglês:

    The determination of conversion during suspension polymerization reactions is not an easy task due to the heterogeneity of the reaction medium and the tendency of particles to agglomerate rapidly when stirring is stopped. Usually, bulk polymerization in ampoules is employed to study the kinetics of suspension polymerization reactions. In this work, a comparison of different techniques for the determination of conversion during suspension polymerization reactions is presented. Results showed a good agreement between the conversion obtained by gravimetry during styrene suspension polymerization and on-line conversion monitoring data using fiber-optic based Raman Spectroscopy. Nevertheless, the polymerization rate of styrene bulk polymerization carried out in ampoules was higher than the real reaction rate of styrene suspension polymerization due to slightly higher reaction temperatures. Simulation results using the experimental temperature data in a mathematical model confirmed these results.
  • Parameter estimation for VLE calculation by global minimization: the genetic algorithm Thermodynamics And Separation Processes

    Alvarez, V. H.; Larico, R.; Ianos, Y.; Aznar, M.

    Resumo em Inglês:

    Vapor-liquid equilibrium calculations require global minimization of deviations in pressure and gas phase compositions. In this work, two versions of a stochastic global optimization technique, the genetic algorithm, the freeware MyGA program, and the modified mMyGA program, are evaluated and compared for vapor-liquid equilibrium problems. Reliable experimental data from the literature on vapor liquid equilibrium for water + formic acid, tert-butanol + 1-butanol and water + 1,2-ethanediol systems were correlated using the Wilson equation for activity coefficients, considering acid association in both liquid and vapor phases. The results show that the modified mMyGA is generally more accurate and reliable than the original MyGA. Next, the mMyGA program is applied to the CO2 + ethanol and CO2 + 1-n-butyl-3-methylimidazolium hexafluorophosphate systems, and the results show a good fit for the data.
  • Extraction of bixin from annatto seeds using supercritical carbon dioxide Thermodynamics And Separation Processes

    Silva, G. F.; Gamarra, Felix M. C.; Oliveira, A. L.; Cabral, F. A.

    Resumo em Inglês:

    The solubility of 93% pure bixin in supercritical carbon dioxide (SC-CO2) and of the bixin present in annatto seeds (Bixa orellana L.) was measured. For the seeds, the measurements were made in a temperature range from 30 to 50ºC and pressure between 10 and 35 MPa and for the pure bixin, at 40ºC from 10 to 35 MPa. The main pigments of annatto seeds are bixin and norbixin, but the extracts only showed the presence of cis and trans-bixin, indicating that norbixin is not soluble in SC-CO2. The annatto seeds used in the experiments contained about 2.7% bixin and 3.1% oil. In the seeds, the crossover point of solubility was at about 28 MPa and values for solubility were about ten times higher than those of the pure bixin, giving evidence that the oil acted as a co-solvent with the CO2.
  • Chemical profile and antimicrobial activity of Boldo (Peumus boldus Molina) extracts obtained by compressed carbon dioxide extraction Thermodynamics And Separation Processes

    Mazutti, M.; Mossi, A. J.; Cansian, R. L.; Corazza, M. L.; Dariva, C.; Oliveira, J. Vladimir

    Resumo em Inglês:

    This work reports the effects of temperature (20 to 50ºC) and pressure (100 to 250 bar) on the extraction yield, chemical characteristics and antimicrobial activity of extracts of Peumus boldus Molina obtained by compressed carbon dioxide extraction. Results showed that the extraction variables affect the extraction yield and the chemical distribution of the major compounds present in the extracts. The extracts were chemically analyzed with regard to 1,8-cineole, trans-sabinene, pinocarveol, pinocarvone, 4-terpineol, ascaridole, piperitone oxide, limonene dioxide and n-eicosane in a GC/MSD. Antimicrobial tests demonstrated that the high-pressure CO2 extracts had activity against 13 bacteria and that better action was verified with extracts obtained at a lower CO2 extraction density and a higher temperature.
  • Errata

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