| 1. |
- Camelini, Carla Maisa, et al.
(författare)
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Production of Exopolysaccharides by Lactobacillus plantarum ATCC 8014 and Concentration by Nanofiltration
- 2016
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Ingår i: JOURNAL OF ADVANCES IN BIOTECHNOLOGY. - : CIRWOLRD. - 2348-6201. ; 06:2, s. 901-912
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Tidskriftsartikel (refereegranskat)abstract
- Functional food may promote specific physiological benefits besides the properties of nourishing and feeding, thanks to the presence of physiologically healthy ingredients such as probiotics and prebiotics. Amongst the probiotics is Lactobacillus plantarum, which belongs to the group of lactic acid bacteria (LAB). Energy obtainment by these microorganisms occurs through carbohydrate fermentation, producing mainly lactic acid but also exopolysaccharides (EPS), which presents technological application on the food industry mainly by their prebiotic properties. In order to enable the obtainment of EPS, a production process of L. plantarum ATCC 8014 was established in aerobic conditions in an airlift bioreactor, using supplemented tofu whey as substrate. The process was compared to the generally employed MRS medium. EPS concentration was performed by nanofiltration (NF), carried at 35 °C and 6 bars, and samples analyzed via HPLC-IR. The cultivation allowed biomass yields of up to 3.2 g/L and 2.7 g/L, and EPS yields of 350 mg/L and 210 mg/L for the TWS and MRS media, respectively. On the NF process, the final concentrated extract was obtained with VRF (volume reduction factor) of 4.0, with increases of up to 80% on EPS contents. During membrane processing, it was verified that the greatest part of the flux resistance (60%) was caused by a polarized gel layer. This study showed that the use of tofu whey is applicable for EPS production and that nanofiltration is an efficient procedure to concentrate the prebiotic compounds obtained during the cultivation of L. plantarum ATCC 8014.
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| 2. |
- Penha, Frederico Marques, et al.
(författare)
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Evaluation of permeation of macauba oil and n-hexane mixtures through polymeric commercial membranes subjected to different pre-treatments
- 2015
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Ingår i: Journal of Food Engineering. - : ELSEVIER SCI LTD. - 0260-8774 .- 1873-5770. ; 155, s. 79-86
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Tidskriftsartikel (refereegranskat)abstract
- Macauba is a Brazilian palm tree with high edible oil productivity and of great interest to many applications. In the oil extraction process, solvent recovery is one point of major concern, due to its high energy consumption and oil quality losses. Those drawbacks can be partially overcome by integration of membrane technology to the usual solvent distillation step. The present work tested four ultrafiltration (UF) and one nanofiltration (NF) membrane (Microdyn-Nadir) on the solvent recovery of synthetic mixtures of macauba oil and n-hexane. Membranes were pre-treated before use with different solvents in specific time lengths, according to preliminary studies. The membrane performance was evaluated by permeate flux and oil retention. Macauba (pulp and kernel) oil was evaluated by determinations of acidity, peroxide value and fatty acid profile. Membranes showed usual flux behaviour, compatible with other studies concerning oil/solvent mixtures permeation, although its values were quite above the expected. Best results for retention (>30%) are related to the membranes with lower molar mass cut-off (MMCO), and the best balance between permeate flux and oil retention was found for the NF membrane (12.4 g m(-2) h(-1), 34.7%).
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| 3. |
- Penha, Frederico Marques, et al.
(författare)
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Influence of different solvent and time of pre-treatment on commercial polymeric ultrafiltration membranes applied to non-aqueous solvent permeation
- 2015
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Ingår i: European Polymer Journal. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0014-3057 .- 1873-1945. ; 66, s. 492-501
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Tidskriftsartikel (refereegranskat)abstract
- Several pre-treatments and solvents were tested through permeation in commercial polymeric membranes (UH004, UP005, UP010 and UH050 - Microdyn-Nadir) with different molar mass cut-offs (4 kDa, 5 kDa, 10 kDa and 50 kDa, respectively), in order to evaluate their efficiency and stability through non-aqueous solvent permeation. After pre-treatments and permeations, membranes were characterised with contact angle, Fourier Transform Infrared Spectroscopy (FTIR), and Field Emission Scanning Electronic Microscopy (FESEM) to evaluate structural integrity. The results of solvent permeation suggest that selectivity of the polymeric matrix depends not only on pore size, but also, in great extent, on the interaction between solvent and polymer. A strong relation can be noted between the conditioning length and permeability for ethanol pre-treatments. Permeability to n-hexane increased from 4 to 18 times after pre-treatment, depending on the time of exposure to ethanol and n-hexane. Characterisation analyses show no significant changes on the membranes surface. In some cases, discrepancies observed among permeate fluxes and contact angles might be an indicative of the occurrence of swelling and plasticisation. However, results suggest the feasibility in the use of these membranes for the recovery of solvents in the oil industry, if suitable process parameters are chosen.
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| 4. |
- Rezzadori, Katia, et al.
(författare)
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Characterization and performance of reverse osmosis and nanofiltration membranes submitted to subcritical and supercritical CO2
- 2017
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Ingår i: Journal of Supercritical Fluids. - : ELSEVIER SCIENCE BV. - 0896-8446 .- 1872-8162. ; 128, s. 39-46
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Tidskriftsartikel (refereegranskat)abstract
- Behavior of nanofiltration (NF270 and NP030) and reverse osmosis (BW30 and ORAK) polymeric membranes in systems with dense CO2 was evaluated. The influence of transmembrane pressure on the CO2 permeate flux at subcritical and supercritical conditions was assessed and membrane characterization (FTIR-ATR, zeta potential, Hansen’s solubility parameters) was performed. The results of CO2 permeation suggest that selectivity of polymeric matrix depends, in great extent, on the interaction between solvent and polymer. This behavior corroborates with the presence of hysteresis phenomenon in permeability curves and solubility results. Also, zeta potential showed a decrease in the membrane point of zero charge (PZC) after pressurization/depressurization cycle, suggesting possible CO2 sorption in the membrane polymer. Nevertheless, the oil retention for NP030 and ORAK membranes was up to 85% and no damage to the membrane structure was found. Both membranes presented potential for concentration of fatty acids under dense phase CO2.
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| 5. |
- Rezzadori, Katia, et al.
(författare)
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Effect of dense CO2 on polymeric reverse osmosis and nanofiltration membranes and permeation of mixtures of macauba oil (Acrocomia aculeata) and CO2
- 2015
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Ingår i: Journal of Membrane Science. - : ELSEVIER SCIENCE BV. - 0376-7388 .- 1873-3123. ; 481, s. 195-206
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Tidskriftsartikel (refereegranskat)abstract
- The performance of four commercial membranes upon subcritical and supercritical CO2 treatments have been characterised by different methods. The membranes were treated up to 8 h in static process, using two different conditions (18 MPa/313.15 K - supercritical and 8 MPa/293.15 K - subcritical). The possible changes in membrane characteristics were investigated by atomic force microscopy (AFM), contact angle and surface free energy, thermogravimetric analysis (TGA), scanning electronic microscopy (SEM). Membrane performance was also evaluated by measuring CO2 flux ancl macauba oil retention factors. Changes in membrane roughness ancl in contact angles were observed for all membranes after sub and supercritical CO2 treatments. Moreover, the surface free energy and the polar component showed a decrease after CO2 exposure, confirming an increase in surface hydrophobicity of membranes detected from contact angle results. This empowerment of hydrophobicity is associated mainly with the CO2-polymer interaction. Other intra and interchain effects should not affect the thermal stability leaving TGA results unchanged after CO2 exposure. ORAK and NP030 membranes showed high macauba oil retentions; 95% and 85%, respectively in supercritical condition. This latter revealed to cause important changes in the membranes due to the higher solubility of CO2 in polymeric matrix at this condition. However, the selectivity was not changed and it is possible to use commercial polymeric membranes in supercritical systems for CO2 regeneration and partial fatty acid fractioning.
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| 6. |
- Rezzadori, Katia, et al.
(författare)
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Evaluation of reverse osmosis and nanofiltration membranes performance in the permeation of organic solvents
- 2015
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Ingår i: Journal of Membrane Science. - : ELSEVIER. - 0376-7388 .- 1873-3123. ; 492, s. 478-489
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to evaluate the influence of different solvents and time conditionings in the permeation of n-hexane and oil/n-hexane solutions through several reverse osmosis (ORAK - Osmonics, BW30 - Dow Filmtec) and nanofiltration (NF270 - Dow Filmtec, NP030 - Microdyn Nadir) polymeric membranes. The study of the influence of membrane conditioning on the n-hexane flux was carried out using different solvents (n-hexane, ethanol, n-propanol, iso-propanol and butanol) as pretreating agents in different time intervals. Membrane performance was tested by measuring n-hexane fluxes and rejections of dissolved castor oil. The conditioning with ethanol increased n-hexane fluxes in the polyamide membranes ORAK, NF270 and BW30, while the polyethersullone membrane NP030 did not present any increase in permeability. An increase in contact angle after membrane conditioning was detected, as well as a reduction in free surface energy. This suggests that pretreatment steps alter the surface hydrophilic character. Salt rejections for all the membranes decreased after the pretreatments and permeation with n-hexane for 8 h. These rejections dropped from 87-99% to 72-77% for membranes NF270, NP030 and BW30; and from 99% to 88% for ORAK, which showed better stability to solvent exposure. For castor oil, the highest retention was 60% for reverse osmosis membrane ORAK. The results obtained in this work with commercial RO and NF membranes, normally used in aqueous solutions operations, indicate that most of these membranes do not present adequate stability towards nonaqueous solvents.
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| 7. |
- Rezzadori, Katia, et al.
(författare)
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Impact of Organic Solvents on Physicochemical Properties of Nanofiltration and Reverse-Osmosis Membranes
- 2019
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Ingår i: Chemical Engineering & Technology. - : WILEY-V C H VERLAG GMBH. - 0930-7516 .- 1521-4125. ; 42:12, SI, s. 2700-2708
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Tidskriftsartikel (refereegranskat)abstract
- Polymeric membranes subjected to the permeation of n-hexane were characterized and the influence of pretreatment with ethanol on the properties of the membranes was studied to assess membrane performance and stability. The results suggest that the selectivity of the membrane depends not only on the pore size, but also to a great extent on the interaction between solvent and polymer. An increase in membrane roughness and contact angle was observed for all membranes after pretreatment with ethanol and n-hexane permeation. Moreover, the surface free energy decreased after solvents exposure, indicating an increase in membrane surface hydrophobicity and polymer swelling. The studied membranes show feasibility of use for the recovery of solvents, if suitable process parameters are selected.
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| 8. |
- Zanatta, Vanessa, et al.
(författare)
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Stability of oil-in-water emulsions produced by membrane emulsification with microporous ceramic membranes
- 2017
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Ingår i: Journal of Food Engineering. - : ELSEVIER SCI LTD. - 0260-8774 .- 1873-5770. ; 195, s. 73-84
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Tidskriftsartikel (refereegranskat)abstract
- Membrane emulsification has been drawing attention due to its many application possibilities. This study aimed to assess the preparation and stability of oil in water (O/W) emulsions by membrane emulsification technique. Microporous ceramic membranes with mean pore size 0.2 mu m and 0.8 mu m were used for producing sunflower oil in water emulsions, displaying mean droplet size ranging from 2.9 to 11.6 mu m and from 4.8 to 16.2 mu m, respectively. The effect of the oil concentration (10%-20%), surfactant concentration (1%-4%), tangential velocity (0.12 m s(-1) to 0.24 m s(-1)), and feed pressure (100 kPa-300 kPa) on the process performance was investigated using an experimental design. All the parameters significantly influenced the mean droplet size, the droplet size distribution, and the emulsion stability. Depending on the emulsification conditions, monodisperse and polydisperse emulsions were obtained. The use of a membrane with 0.2 mu m mean pore size led to better results than those obtained with a 0.8 mu m membrane, since they yielded emulsions displaying smaller droplet size and narrower size distribution. The emulsions prepared using this membrane were stable up to 100 days. (C) 2016 Elsevier Ltd. All rights reserved.
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| 9. |
- Zin, Guilherme, et al.
(författare)
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Fouling control in ultrafiltration of bovine serum albumin and milk by the use of permanent magnetic field
- 2016
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Ingår i: Journal of Food Engineering. - : ELSEVIER SCI LTD. - 0260-8774 .- 1873-5770. ; 168, s. 154-159
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Tidskriftsartikel (refereegranskat)abstract
- Membrane separation processes are widely employed for protein concentration in the food industry. The major drawback is permeability reduction caused by concentration polarization and fouling. The present work evaluated the influence of a permanent magnetic field applied to the ultrafiltration process (UF) of protein solutions, as an alternative to improve the permeation performance and the permeability recovery. Permeation tests of bovine serum albumin (BSA) and milk as the feed protein solutions through a 50 kDa hydrophilic polyethersulfone (PES) membrane were carried out in a tangential flow module. The feed pH was varied (4.0, 6.5 and 8.0) and ionic strength was modified by sodium chloride (NaCl). Permanent magnets were placed so as to obtain a maximum 0.7 T magnetic field perpendicular to the membrane surface. The magnetic induction effect (MI) on the feed solutions was also studied by submitting the feed to the magnetic field for 2 h before permeation run. The presence of magnetic field and the MI effect of the solution were effective in increasing both the permeate flux and the recovery of hydraulic permeability. The magnetic field application in the UF of protein solutions has proven to be an attractive alternative for improving process performance. (C) 2015 Elsevier Ltd. All rights reserved.
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