Scielo RSS <![CDATA[Brazilian Journal of Chemical Engineering]]> vol. 34 num. 2 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[Microbial growth models: A general mathematical approach to obtain <em>μ</em> <sub><em>max</em></sub> and <em>λ</em> parameters from sigmoidal empirical primary models]]> Abstract Empirical sigmoidal models have been widely applied as primary models to describe microbial growth in foods. In predictive microbiology, the maximum specific growth rate (µ max ) and the lag phase (λ) are the parameters of some models and have been considered as biological parameters. The objective of the current study was to propose mathematical equations to obtain the parameters μ max and λ for any sigmoidal empirical growth model. In a case study, the performance was compared of two models based on empirical parameters and two models based on biological parameters. These models were fitted to experimental data for Lactobacillus plantarum in six isothermal conditions. Some advantages of the proposed approach were the practical and biological interpretation of these parameters, and the useful information of the secondary modeling describing the dependence of µ max and λ with the temperature. <![CDATA[Optimization of solid-state fermentation for bioherbicide production by <em>Phoma</em> sp <em>.</em>]]> Abstract In this work the bioherbicide production from Phoma sp. by solid-state fermentation was optimized. Agroindustrial residues such as bagasse, soybean bran and corn steep liquor were used as substrate. The bioherbicide was extracted from the fermented solid and the supernatant was applied for the control of the target plant. The evaluated responses in the bioassay were plant height, root length, fresh and dry weight, number of flowers and phytotoxicity. The results in the bioassays demonstrated that the bioherbicide presented activity towards the target plant and the intensity of the effect was influenced by the formulation of the fermentation medium. The optimized condition for bioherbicide production was (wt%): moisture content 70.0, soybean bran content 30.0 and corn steep liquor (CSL) 20.0, it being possible to obtain an injury phytotoxicity level of 40. The bioherbicide showed a mode of action based on the inhibition of carotenoid biosynthesis. <![CDATA[Determination of acoustic fields in acidic suspensions of peanut shell during pretreatment with high-intensity ultrasound]]> Abstract The benefits of high-intensity ultrasound in diverse processes have stimulated many studies based on biomass pretreatment. In order to improve processes involving ultrasound, a calorimetric method has been widely used to measure the real power absorbed by the material as well as the cavitation effects. Peanut shells, a byproduct of peanut processing, were immersed in acidified aqueous solutions and submitted to an ultrasonic field. Acoustic power absorbed, acoustic intensity and power yield were obtained through specific heat determination and experimental data were modeled in different conditions. Specific heat values ranged from 3537.0 to 4190.6 J·kg-1·K-1, with lower values encountered for more concentrated biomass suspensions. The acoustic power transmitted and acoustic intensity varied linearly with the applied power and quadratically with solids concentration, reaching maximum values at higher applied nominal power and for less concentrated suspensions. A power yield of 82.7% was reached for dilute suspensions at 320 W, while 6.4% efficiency was observed for a concentrated suspension at low input energy (80 W). <![CDATA[Influence of toluene and salinity on biosurfactant production by <em>Bacillus</em> sp.: scale up from flasks to a bench-scale bioreactor]]> ABSTRACT To select the best biosurfactant producer, Pseudomonas putida, Bacillus megatherium, Bacillus licheniformis and Bacillus subtilis were cultured in flasks on media with different salinity [low salinity (LS), Bushnell-Haas (BH) and artificial sea water (SW) media] supplemented or not with toluene as a model pollutant. Toluene inhibited the growth of all microorganisms and stimulated the biosurfactant production. B. subtilis exhibited the best performance, being able to lower the surface tension (ST) in the LS medium to 65.5 mN/min in the absence of toluene, and to 46.5 mN/min in the BH medium in the presence of toluene, corresponding to ST reductions of 13.0 and 27.5 mN/m, respectively. Scaling up the process to a bench-scale fermentor, the best results were obtained in the LS medium, where B. subtilis was able to reduce the toluene concentration from 26.0 to 4.3 g/L within 12 h and ST by 17.2 mN/m within 18 h. The results of this study point out that B. subtilis is an interesting biosurfactant producer, which could be used in the bioremediation of toluene-contaminated water. <![CDATA[<em>Zymomonas mobilis</em> IMMOBILIZED ON LOOFA SPONGE AND SUGARCANE BAGASSE FOR LEVAN AND ETHANOL PRODUCTION USING REPEATED BATCH FERMENTATION]]> Abstract Two experiments were carried out using loofa sponge and sugarcane bagasse as immobilization support. First a 2(5-2) design of experiments was realized with the following independent variables: sucrose concentration; pH; incubation time and agitation. Based on the best results observed in this experiment, the capacity for reuse of the supports in subsequent fermentations was evaluated for 12 recycle days. Loofa sponge support was the best immobilization support and in the 2(5-2) experiment, it showed 2.58 g.L-1 of immobilized cells and 19.13 g.L-1 of exopolysaccharide levan. Sugarcane bagasse showed the highest ethanol production (103.82 g.L-1). In the immobilization support recycling experiment, sugarcane bagasse was the most promising support since it showed cell viability up to the last fermentation cycle, confirmed by scanning electronic microscopy, also showing the largest values for immobilized biomass (3.23 g.L-1), levan (32.13 g.L-1), ethanol (148.18 g.L-1) and sucrose consumption (92.64%). <![CDATA[LIPASE PRODUCTION BY <em>Aspergillus niger</em> GROWN IN DIFFERENT AGRO-INDUSTRIAL WASTES BY SOLID-STATE FERMENTATION]]> ABSTRACT Filamentous fungi can easily degrade agro-industrial wastes in solid-state fermentation processes, synthesizing many important commercial biocompounds, such as lipolytic enzymes. The aim of this study was to evaluate the effect of the composition of the solid culture medium on the production of lipolytic enzymes by the fungus Aspergillus niger. Rice, wheat and soybean bran were mixed to prepare the culture medium, which was supplemented with glucose, glycerol or soybean oil. Four mixture experimental designs were used to find the best medium for enzyme production. According to our results, the highest lipolytic activity values were achieved with a mixture of rice bran and glycerol (19.844 U·g-1) or with rice bran only (13.267 U·g-1). Thus, the lipolytic enzyme could be produced without any additional carbon source apart from rice bran, although glycerol addition induced a higher production. <![CDATA[Temperature, pH and carbon source affect drastically indole acetic acid production of plant growth promoting yeasts]]> Abstract Rhizosphere and phylloplane yeasts are able to produce phytohormones, acting as potential plant growth promoters. The aim of this study was to analyze the production of indole acetic acid (IAA) by yeasts using variations in the culture conditions. The yeasts evaluated were Rhodotorula mucilaginosa and Trichosporon asahii, which were cultivated in a potato broth medium with 20 g/L of glucose or sucrose as the carbon source. The cultivation was carried out at 22°C, 25°C or 30°C, and the initial pH was adjusted to 3.0, 4.5 or 6.0. The cultures were analyzed using a colorimetric technique with Salkowski reagent. The cell count was determined in all of the conditions. The results for T. asahii showed that IAA production with sucrose was superior at pH 6.0, and that with glucose was superior at pH 4.5. These results indicate an association between the carbon source and medium pH. Rh. mucilaginosa (2F32) presented a high IAA production when compared with T. asahii (3S44 and 4C06) or even with other microorganisms referenced in the literature. The highest production (0.655 g/L) was obtained at pH 6.0 with glucose as the carbon source. Variations in the culture conditions did not affect the cell growth of the yeasts. <![CDATA[Potassium biphthalate buffer for pH control to optimize glycosyl hydrolase production in shake flasks using filamentous fungi]]> Abstract The optimization of culture medium with statistical methods is widely used in filamentous fungi glycosyl hydrolase production. The implementation of such methodology in bioreactors is very expensive as it requires several pH-controlled systems operating in parallel in order to test a large number of culture media components. The objective of this study was to evaluate potassium biphthalate buffer for pH control, which allows the optimization studies to be performed in shake flasks.The results have shown that buffering the culture medium with 0.1 M potassium biphthalate allowed pH control, resulting in a decrease of the standard deviation of triplicates for pH and activities of glycosyl hydrolase measurements. The use of this buffer allowed shake flask culture media optimization of enzyme production by Trichoderma harzianum, increasing the cellulase activity by more than 2 times compared to standard unbuffered culture medium. The same buffer can be used for culture media optimization of other fungi, such as Penicillium echinulatum. <![CDATA[Functionalized agarose as an effective and novel matrix for immobilizing <em>Cicer arietinum</em> β-galactosidase and its application in lactose hydrolysis]]> Abstract The present study demonstrates the immobilization of β-galactosidase from Cicer arietinum on a simple and inexpensive matrix, glutaraldehyde functionalized agarose (GFA), to suggest its potential application in hydrolyzing whey lactose in biotechnology industries. The designed matrix provided large surface area for the immobilization of β-galactosidase, apart from exhibiting greater biocatalytic activity in terms of selectivity, loading and stability. GFA retained 83% enzyme activity as a result of immobilization. Soluble and GFA bound Cicer arietinum β-galactosidase showed the same pH and temperature-optima at pH 5.0 and at 50 °C, respectively. However, immobilized enzyme exhibited a greater fraction of activity at both acidic and basic pH, and at higher temperature ranges. GFA bound enzyme lost only 20 % enzyme in the presence of 3% galactose, and retained 70 % activity even after its sixth repeated use. Immobilized enzyme showed pronounced lactose hydrolysis from whey in batch processes at 55 °C as compared to enzyme in solution. <![CDATA[Real time and <em>in situ</em> Near-Infrared Spectroscopy (Nirs) for Quantitative Monitoring of Biomass, Glucose, Ethanol and Glycerine concentrations in an alcoholic fermentation]]> Abstract This study investigates the application of NIR spectroscopy for real-time monitoring of process parameters in alcoholic fermentations. For this purpose, fermentation batches using Saccharomyces cerevisiae were carried out and monitored in situ by an immersed NIRS probe. Samples were collected throughout the fermentations, and concentrations of biomass, glucose, ethanol and glycerin were analyzed by reference methods and multivariate data analyses such as PCA and PLSR. PCA was used to investigate data variability and to select samples for calibration and for external validation sets. A PLSR model for biomass yielded R2 and RMSEP values of 0.99 and 0.276 g.L-1, respectively. For glucose, the carbon source, the PLSR model yielded an R2 of 0.95 and an RMSEP of 7.14 g.L-1. The PLSR model for ethanol was characterized by an R2 of 0.95 and an RMSEP of 0.06 g.L-1. For glycerin, a highly accurate PLSR model with an R2 of 0.98 and an RMSEP of 0.116 g.L-1 was obtained. These results indicate that an in situ NIRS probe is suitable for real-time monitoring of important parameters in alcoholic fermentations. <![CDATA[Adaptation behaviour of bacterial species and impact on the biodegradation of biodiesel-diesel]]> Abstract Two bacteria, namely Bacillus subtilis and Pseudomonas aeruginosa were exposed to different concentrations of diesel to increase their adaptation to the fossil fuel, and were used for the degradation of diesel-biodiesel blends. The biodegradation rate was evaluated using the redox indicator 2,6-dichlorophenol indophenol (DCPIP) test and gravimetric analysis. The preliminary exposure of cells to diesel proved to improve their biodegradation capacities, and exposure to a higher concentration (70%) of diesel resulted in maximum biodegradation of up to 58.38 g and 1.78 g of degraded oil per CFU/mL (1010) for P. aeruginosa and B. subtilis respectively. It was found that the adapted cells preferably used diesel in the blend. P. aeruginosa and B. subtilis exhibited different adaptation capabilities and biodegradation behaviour. Biodiesel stimulated the biodegradation of the diesel-biodiesel blends by non-adapted cells only; the adapted cells exhibited a different behaviour. <![CDATA[ANAEROBIC DIGESTION OF MUNICIPAL BIOWASTE FOR THE PRODUCTION OF RENEWABLE ENERGY: EFFECT OF PARTICLE SIZE]]> Abstract In recent years, Anaerobic Digestion (AD) has become an important technological alternative for the management of municipal biowaste (MBW) for both pollution control and obtaining renewable energy such as methane. One of the factors that most affects the AD of MBW is the particle size, particularly in the hydrolysis and lag phases, this last being in general the limiting stage of solid waste AD. This research evaluated on a laboratory scale the AD of MBW by evaluating Biochemical Methane Potential (BMP) at a temperature of 30 °C during 30 days and the influence of particle size. The particle sizes ranged between &lt; 2 mm to 12.5 mm. Along the study, better results were observed for particle sizes &lt; 2 mm, obtaining productions of methane and electrical energy of 128 mL gVS-1 and 2960.4 kWh week-1 respectively (19% higher than in reactors with larger particles), thus indicating lower costs for design and maintenance. <![CDATA[Hydrodynamics of an external-loop airlift reactor with inserted membrane]]> Abstract The objective of this study was to investigate the hydrodynamics of an external-loop airlift membrane reactor (ELAMR). The ELAMR was operated in two modes: without (mode A) and with bubbles in the downcomer (mode B), depending on the liquid level in the gas separator. The influence of the gas distributor’s geometry and various alcohol solutions on the hydrodynamics of the ELAMR was studied. Results for the gas holdup and the downcomer liquid velocity are commented with respect to an external-loop airlift reactor of the same geometry but without the membrane in the downcomer (ELAR). Due to the presence of the membrane in the downcomer, acting as the local hydrodynamic resistance, the gas holdup in the riser of the ELAMR increases maximally by 16%, while the liquid velocity in the downcomer decreases up to 50%. The values of the gas holdup and liquid velocity predicted by the application of empirical power law correlations and a feed forward back propagation neural network (ANN) are in very good agreement with experimental values. <![CDATA[Two-dimensional Flow of Power-law Fluids over a Pair of Cylinders in a Side-by-Side Arrangement in the Laminar Regime]]> Abstract This manuscript presents the effect of Reynolds number (Re) and proximity of the bodies on the hydrodynamics of flow of shear-thinning, Newtonian and shear-thickening fluids over a pair of cylinders kept in side-by-side arrangement. Results obtained from the numerical simulations carried out with a combination of different parameters in the range of 0.2 ≤ power law index (n) ≤ 1.8, 0.1 ≤ Re ≤ 100 and 1.2 ≤ G (gap between the cylinders/diameter) ≤ 4 have been discussed in details. Analysis of the results gives a clear insight into the complex influence of Re on streamline patterns, surface pressure profiles, drag and lift coefficients for various fluids when the gap between two cylinder is changed. <![CDATA[Lipase-catalyzed ethanolysis of <em>Jatropha curcas</em> L. oil assisted by ultrasonication]]> ABSTRACT Transesterification of non-edible oils using immobilized lipase is a promising process for biodiesel production. Thus, this study aimed to evaluate the enzymatic transesterification of the non-edible Jatropha curcas oil for FAEE production under ultrasound irradiation in a solvent-free system. The effects of enzyme concentration, water concentration, molar ratio of ethanol to oil and ultrasound power on the FAEE conversion have been evaluated. The results show that enzyme concentration and irradiation power have a positive significant effect on FAEE conversion, where an increase in these variables leads to higher conversions. Conversion above 54% of FAEE was achieved with 1.5 hours of reaction time using ultrasound irradiation, reducing reaction time by at least 3 times, when compared with the same experimental conditions without ultrasound irradiation. Results showed that ultrasound can improve reaction conversion mainly by enhancing the mass transfer between the constituents of the reactions. <![CDATA[CFD Simulation of an Industrial Reactor for Thermal Cracking of 1,2-Dichloroethane]]> Abstract The vinyl chloride monomer (VCM) is commercially produced on a large scale by thermal cracking of 1,2-dichloroethane (EDC) in a tubular reactor immersed in a furnace. Computational fluid dynamics (CFD) was used to simulate and predict the performance of an industrial reactor. The reactor conversion as well as the behavior of several process variables such as pressure, temperature, velocity and concentration of components through the reactor were predicted in this work.The results were compared with industrial data and are in agreement with them. <![CDATA[BIODEGRADATION OF ACRYLIC PAINTS: PROCESS MODELLING OF BIOCIDE EFFECT ON BIOMASS GROWTH AT DIFFERENT TEMPERATURES]]> Abstract Acrylic paint, notwithstanding the attention paid during the production process, couldbe contaminated by bacteria. This is a consequence of microbiological residuals on the can, resulting in the alterationof paint characteristics. It is therefore necessary to provide an in-canpreservation of the paint by using a biocide.In this paper, the evolution of an in-can system, using a thermo-fluid dynamic model is presented; as a biocide, 2-methyl-4-isothiazolin-3-one, commercially known as MIT,was considered. The model was implemented on gPROMSsoftware and it was possible to determine the inhibitory concentration of the biocideinorder to guarantee both the protection of the can and the protection of thecover phase. To develop the model, kinetic parameters have been found by fitting available literature experimental data. As far as the thermodynamical parameters, theequilibrium between liquid and vapor phases was described bythe NRTLmodel (ASPEN Plus). The model has been validated through a comparison with experimental literature results using MIT alone and a mixture of biocides (MIT/BIT). The main results are that,at the maximum allowable concentration (100 ppm as imposed by law), the MIT biocide is able to protectthe paint for long periods, even when the temperature varies cyclically from 10 to 40°C. <![CDATA[RED WINE EXTRACT OBTAINED BY MEMBRANE-BASED SUPERCRITICAL FLUID EXTRACTION: PRELIMINARY CHARACTERIZATION OF CHEMICAL PROPERTIES.]]> ABSTRACT This study aims to obtain an extract from red wine by using membrane-based supercritical fluid extraction. This technique involves the use of porous membranes as contactors during the dense gas extraction process from liquid matrices. In this work, a Cabernet Sauvignon wine extract was obtained from supercritical fluid extraction using pressurized carbon dioxide as solvent and a hollow fiber contactor as extraction setup. The process was continuously conducted at pressures between 12 and 18 MPa and temperatures ranged from 30 to 50ºC. Meanwhile, flow rates of feed wine and supercritical CO2 varied from 0.1 to 0.5 mL min-1 and from 60 to 80 mL min-1 (NCPT), respectively. From extraction assays, the highest extraction percentage value obtained from the total amount of phenolic compounds was 14% in only one extraction step at 18MPa and 35ºC. A summarized chemical characterization of the obtained extract is reported in this work; one of the main compounds in this extract could be a low molecular weight organic acid with aromatic structure and methyl and carboxyl groups. Finally, this preliminary characterization of this extract shows a remarkable ORAC value equal to 101737 ± 5324 µmol Trolox equivalents (TE) per 100 g of extract. <![CDATA[Oil Removal from Produced Water by Ultrafiltration using Polysulfone Membrane]]> Abstract The present paper deals with the ultrafiltration (UF) of produced water using a polysulfone membrane. Membranes were prepared by the phase inversion technique using polysulfone (PSf) polymer base, poly vinyl pyrrolidone (PVP) additive and N-methyl-2-pyrrolidone (NMP) solvent. Prepared UF membranes were characterized by determining the surface morphology by scannaing electron microscopy (SEM), atomic force microscopy (AFM), porosity, (iii) water contact angle, equilibrium water content and pure water flux, whereas membrane performance was determined by measuring permeate flux and oil rejection using oily synthetic produced water. With the increase in trans-membrane pressure in the cell, the permeate flux increased significantly, but oil rejection showed a decreasing trend. The best UF membrane performance under different trans-membrane pressures was obtained by maintaining (90% oil rejection using an UF membrane with the following composition: PSf- 15%, PVP - 5% and NMP - 80%. <![CDATA[Experimental studies of CO<sub>2</sub> absorption enhancement in water-based nanofluids of carbon nanotubes]]> Abstract The improvement of CO2 absorption by CNT nanofluids with deionized water as the base fluid was studied experimentally. The reactor used was a stirred thermostatic reactor, operated batchwise. Pure CO2 was employed in all the experiments. The content of CNTs in the nanofluids ranged from 0 to 0.2% (wt). The acidification treatment of CNTs was employed to improve the stability of the nanofluids. The parameters, such as the concentration of CNT nanoparticles in the nanofluids, the stirring speed, the ultrasonic time for CNT nanofluid preparation, the nitration time and the amount of nitric acid for CNT acidification were varied. The results show that, with the increase of CNT concentration, the enhancement factor first increased and then leveled off after a certain value of the CNT concentration. With increasing stirring speed, the enhancement factor in stable functional CNT nanofluids declines monotonously, while in poorly dispersed raw CNT suspensions, it first increased and then reduced. The ultrasonic and nitration times and the amount of nitric acid have optimum values for the CO2 absorption enhancement. The mechanism of the CNT nanofluid enhancement of CO2 absorption is discussed accordingly. The absorption enhancement by the CNT nanofluid should be mainly attributable to convective motion induced by the Brownian motion and the shuttle effect. <![CDATA[Analysis and extension of the Furter equation, and its application in the simulation of saline extractive distillation columns]]> ABSTRACT Simulation of saline extractive distillation columns is a difficult task owing to the high nonlinearity of the rigorous models that represent these systems. The use of simple models to obtain initial estimates of equilibrium compositions may improve the stability and rate of convergence. One of the simplest models to study the vapor-liquid equilibrium of binary liquid mixtures + salt systems is the Furter equation. This model was analyzed in the present work by means of the incorporation of activity coefficient models in the ratio of relative volatility. This approach allowed systematic extensions of the Furter equation and a brief review of the theoretical basis of the original equation. As a result of these extensions, two simple equations were proposed and tested with experimental data from 20 systems, including binary liquid mixtures + salt systems and binary liquid mixtures + ionic liquid systems. Finally, one of these proposed equations was incorporated into the GKTM software in order to assess the utility of these simple models in the simulation of saline extractive distillation columns. The obtained results showed a significant improvement over the previous algorithm.