Helen Conceição Ferraz

Recent achievements in facilitated transport membranes for separation processes

Membrane separation processes have been extensively used for some important industrial separations, substituting traditional methods. However, some applications require the development of new membranes. In this work, we discuss recent progress achieved in this field, focusing on gas and liquid separation using facilitated transport membranes. The advantages of using a carrier species either in a liquid membrane or fixed in a polymer matrix to enhance both the flux and the selectivity of the transport are summarized. The most probable transport mechanisms in these membranes are presented and the improvements needed to spread this technology are also discussed. As examples, we discuss our very successful experiences in air fractioning, olefin/paraffin separation and sugar recovery using liquid and fixed carrier membranes.

Structural Stability of Myoglobin in Organic Media

The structural stability of metmyoglobin in organic solvents and cosolvents was investigated aiming the choice of a suitable medium to perform its dissolution with maintenance of the native folding. The spectroscopic behavior of metmyoglobin solution in UV–Visible and circular dichroism was used to evaluate the solubility and the secondary structure. The results were dependable of the chemical structure of the organic compounds, their polarity and content, in the case of cosolvents. Protic solvents showed better ability than the aprotic ones for the biomolecule dissolution, since they are able to establish hydrogen bonds. Solvents with high polarity usually damage the secondary structure of the protein. Myoglobin was dissolved in pure methanol, ethylene glycol and glycerol. The secondary structure was retained in some extent. The controlled addition of sodium dodecyl sulfate to myoglobin aqueous solution changed the surface moiety of the protein. The complex was extracted to hexane with efficiency of 77%.

Anion-exchange purification of recombinant factor IX from cell culture supernatant using different chromatography supports

Both recombinant and plasma-derived factor IX concentrates are used in replacement therapies for the treatment of haemophilia B. In the present work, the capture step for a recombinant FIX (rFIX) purification process was investigated. Different strong anion-exchange chromatography media (the resins Q Sepharose(®) FF and Fractogel(®) TMAE, the monolith CIM(®) QA and the membrane adsorber Sartobind(®) Q) were tested for their rFIX binding capacity under dynamic conditions. In these experiments, crude supernatant from CHO cells was used, thus in the presence of supernatant contaminants and mimicking process conditions. The highest dynamic binding capacity was obtained for the monolith, which was then further investigated. To study pseudoaffinity elution of functional rFIX with Ca(2+) ions, a design of experiments to evaluate the effects of pH, NaCl and CaCl2 on yield and purification factor was carried out. The effect of pH was not statistically significant, and a combination of no NaCl and 45mM CaCl2 yielded a good purification factor combined with a high yield of active rFIX. Under these conditions, activity yield of rFIX was higher than the mass yield, confirming selective elution of functional, γ-carboxylated rFIX. Scaling-up of this process 8 fold resulted in very similar process performance. Monitoring of the undesired activated FIX (FIXa) revealed that the FIXa/FIX ratio (1.94%) was higher in the eluate than in the loaded sample, but was still within an acceptable range. HCP and DNA clearances were high (1256 and 7182 fold, respectively), indicating that the proposed process is adequate for the intended rFIX capture step.

Evaluation of the Stability of Concentrated Emulsions for Lemon Beverages Using Sequential Experimental Designs

The study of the stability of concentrated oil-in-water emulsions is imperative to provide a scientific approach for an important problem in the beverage industry, contributing to abolish the empiricism still present nowadays. The use of these emulsions would directly imply a reduction of transportation costs between production and the sales points, where dilution takes place. The goal of this research was to evaluate the influence of the main components of a lemon emulsion on its stability, aiming to maximize the concentration of oil in the beverage and to correlate its physicochemical characteristics to product stability, allowing an increase of shelf life of the final product. For this purpose, analyses of surface and interface tension, electrokinetic potential, particle size and rheological properties of the emulsions were conducted. A 24-1 fractional factorial design was performed with the following variables: lemon oil/water ratio (30% to 50%), starch and Arabic gum concentrations (0% to 30%) and dioctyl sodium sulfosuccinate (0 mg/L to 100 mg/L), including an evaluation of the responses at the central conditions of each variable. Sequentially, a full design was prepared to evaluate the two most influential variables obtained in the first plan, in which concentration of starch and gum ranged from 0% to 20%, while concentration of lemon oil/water ratio was fixed at 50%, without dioctyl sodium sulfosuccinate. Concentrated emulsions with stability superior to 15 days were obtained with either starch or Arabic gum and 50% lemon oil. The most stable formulations presented viscosity over 100 cP and ratio between the surface tension of the emulsion and the mucilage of over 1. These two answers were selected, since they better represent the behavior of emulsions in terms of stability and could be used as tools for an initial selection of the most promising formulations.

Sorbitol and gluconic acid production using permeabilized Zymomonas mobilis cells confined by hollow-fiber membranes

Immobilization of Zymomonas mobilis by different methods was investigated. Experiments were performed order to choose the most appropriate support for the immobilization of the cells. The most advantageous option was to use permeabilized cells in the bore of microporous hollow fibers. Whereas the reaction rate was about 33 g of gluconate/ (g of protein·h) using hollow fibers, which is comparable to that observed by using free cells, the calcium alginate immobilized cells presented a reaction rate of 4 g of gluconate/ (g of protein·h). These results can be explained by the mass transfer resistance effect, which, indeed, was much lower in the case of hollow-fiber membranes than in the alginate gel beads. A loss of enzymatic activity during the reaction was observed in all experiments, which was attributed to the lactone produced as an intermediate of the reaction.

Nanostructured screen-printed electrodes based on titanate nanowires for biosensing applications

This work demonstrates the successful modification of screen-printed electrodes using functionalized titanate nanowires for producing a peroxide biosensor. Titanate nanowires were synthesized by the hydrothermal method and characterized using physico-chemical techniques. The surface of the nanowires was modified with (3-aminopropyl)trimethoxysilane and glutaraldehyde to immobilize horseradish peroxidase through covalent bound, obtaining a surface coverage of 1.62mg of enzyme/m2. The surface of screen-printed carbon electrodes was modified with peroxidase-containing nanowires. Cyclic voltammetry and chronoamperometry were employed to study the electrochemical properties of the nanostructured electrode. A low hydrogen peroxide reduction potential around -0.98V (vs Ag, pH7.0) was observed, with linear response in the range of 40 to 560μmolL-1, detection limit of 10.7μmolL-1 and good stability. Reproducibility relative standard deviation was as low as 4.7%. For repeatability, deviation was 3.3%.

Analysis of experimental errors in bioprocesses. 1. Production of lactobionic acid and sorbitol using the GFOR (glucose-fructose oxidoreductase) enzyme from permeabilized cells of Zymomonas mobilis

The proper determination of experimental errors in bioprocesses can be very important because experimental errors can exert a major impact on the analysis of experimental results. Despite this, the effect of experimental errors on the analysis of bioprocess data has been largely overlooked in the literature. For this reason, we performed detailed statistical analyses of experimental errors obtained during the production of lactobionic acid and sorbitol in a system utilizing as catalyst the GFOR (glucose-fructose oxidoreductase) enzyme from permeabilized cells of the bacteria Zymomonas mobilis. The magnitude of the experimental errors thus obtained were then correlated with the process operation conditions and with the composition of the culture media used for bacterial growth. It is shown that experimental errors can depend very significantly on the operation conditions and affect the interpretation of available experimental data. More specifically, in this study, experimental errors depended on the nutritional supplements added to the cultivation medium, the inoculation process, and the reaction time, which may be of fundamental importance for actual process development. The results obtained also indicate, for the first time, that GFOR activity can be affected by the composition of the medium in which cells are cultivated.

Encapsulation of α-tocopherol and β-carotene in concentrated oil-in-water beverage emulsions stabilized with whey protein isolate

ABSTRACT The stabilization of flavor emulsions is a challenge for the industry of functional beverages. In this work, whey protein isolate was used as the stabilizing agent in concentrated orange oil-in-water emulsions. A 23 factorial design was performed, varying the ratio of orange oil/water (30–60%), the concentration of whey protein (1–15%), and the concentration of the surfactant dioctyl sulfosuccinate sodium (0–100 mg L−1). Analyses of surface tension, film formation, zeta potential, particle size, and turbidity were performed. Stable emulsions containing 60% of oil phase were prepared. β-Carotene and α-tocopherol were successfully encapsulated, without affecting the emulsions stability. GRAPHICAL ABSTRACT

Adsorption of Myoglobin onto Hydroxyapatite Modified with Metal Ions

Optimization of the purification process remains a challenge in the production of proteins for pharmaceutical or industrial applications. In this context, the purpose of this work was to study the adsorption of myoglobin onto hydroxyapatite (HAp) modified with metal ions (Cu2+, Ni2+, Zn2+), with the aim of its purification from a complex medium. The influence of pH and ionic strength on the adsorption process was evaluated using experimental design methodology. Experiments for determining the kinetics and adsorption isotherms were undertaken, allowing the determination of important equilibrium parameters required for scale-up. High adsorption capacities (ca. 90 mg myoglobin/g modified HAp) and rapid adsorption kinetics were observed. These results indicate the applicability of HAp as a support for pseudo-affinity chromatography.

Development of functionalized polyetherimide/polyvinylpyrrolidone membranes for application in hemodialysis

The present study aimed to synthesize membranes for hemodialysis based on polyetherimide (PEI) and polyvinylpyrrolidone (PVP), with chemical immobilization of heparin on its surface to increase blood compatibility. The synthesized PEI/PVP membranes were characterized by morphological analysis and transport properties, as well by infrared spectroscopy (FT-IR), protein adsorption, contact angle, activated partial thromboplastin time (aPTT), and platelet adhesion. Hydraulic permeability of the synthesized PEI membranes were comparable to those of current high flux clinical membranes; values of diffusive permeability and rejection for typical solutes were similar to those reported in literature. The immobilization of heparin, in turn, resulted in more hydrophilic membranes, with insignificant protein adsorption and platelet adhesion (as opposed to actual clinical membranes), indicating anti-thrombogenic characteristics as confirmed by increased aPTT.Graphical abstract