Flavio Faria de Moraes

A comparative study on fungal laccases immobilized on chitosan

The phenoloxidase enzyme laccase from the cultures of the Pleurotus ostreatus and Botryosphaeria sp. and a commercial laccase from Aspergillus sp. were immobilized on chitosan of pharmaceutical degree by adsorption followed by crosslinking. Different immobilization conditions in relation to the granulometry of support and amount of enzymatic laccase extract used were tested, aiming at reaching high enzymatic activity with the immobilized enzyme. Two different substrates, ABTS and DMP, were used for the determination of enzymatic activity. The highest enzymatic activity was obtained when 1.0mg/mL of the enzymatic laccase extract from Botryosphaeria sp. was used with 1.0g of support (200 mesh). These immobilized enzymes are to be applied to the improvement of white wines by the degradation of undesirable phenolic compounds.

Controlled release of microencapsulated citronella essential oil on cotton and polyester matrices

Microencapsulated finishes are an important element in the development of new textiles. In this context, a large area to be explored is microencapsulation of essential oils in textiles. This technique offers the possibility of developing new products with many advantages over traditional fabrics, as traditional finishing may be ineffective for reasons related to uncontrolled release of the active principle while microencapsulation aims to achieve increased duration of the finishing effect. However, many studies present only the application of microcapsules in a textile but do not report how the release of the encapsulated material occurs or the influence of the textile matrix. This paper reports the mechanism and kinetics of controlled release of microencapsulated citronella oil in cotton and polyester. The microencapsulation was done by complex coacervation with gelatin and gum Arabic as shell materials. The resulting microcapsules were analyzed by optical microscopy, scanning electron microscopy, thermogravimetric analysis, and dynamic light scattering. They were then applied in cotton and polyester and evaluated by attenuated total reflection Fourier-transform infrared spectroscopy. Finally, the controlled release of citronella from the microcapsules deposited on the fabrics was studied inxa0vitro. It was found that the release was directly influenced by the type of fiber: the microcapsules in polyester showed diffusion by a Fickian mechanism, while a non-Fickian kinetic model fit for the modified cotton. Comprehension of such controlled release processes is fundamental for achieving and developing more durable finishing effects.

Parametric study of hydrogen production from ethanol steam reforming in a membrane microreactor

Microreactors are miniaturized chemical reaction systems, which contain reaction channels with characteristic dimensions in the range of 10-500 µm. One possible application for microreactors is the conversion of ethanol to hydrogen used in fuel cells to generate electricity. In this paper a rigorous isothermal, steady-state two-dimensional model was developed to simulate the behavior of a membrane microreactor based on the hydrogen yield from ethanol steam reforming. Furthermore, this membrane microreactor is compared to a membraneless microreactor. A potential advantage of the membrane microreactor is the fact that both ethanol steam reforming and the separation of hydrogen by a permselective membrane occur in one single microdevice. The simulation results for steam reforming yields are in agreement with experimental data found in the literature. The results show that the membrane microreactorpermits a hydrogen yield of up to 0.833 which is more than twice that generated by the membraneless reactor. More than 80% of the generated hydrogen permeates through the membrane and, due to its high selectivity, the membrane microreactor delivers high-purity hydrogen to the fuel cell.

Characterization of Biocatalysts Prepared with Thermomyces lanuginosus Lipase and Different Silica Precursors, Dried using Aerogel and Xerogel Techniques

The use of lipases in industrial processes can result in products with high levels of purity and at the same time reduce pollutant generation and improve both selectivity and yields. In this work, lipase from Thermomyces lanuginosus was immobilized using two different techniques. The first involves the hydrolysis/polycondensation of a silica precursor (tetramethoxysilane (TMOS)) at neutral pH and ambient temperature, and the second one uses tetraethoxysilane (TEOS) as the silica precursor, involving the hydrolysis and polycondensation of the alkoxide in appropriate solvents. After immobilization, the enzymatic preparations were dried using the aerogel and xerogel techniques and then characterized in terms of their hydrolytic activities using a titrimetric method with olive oil and by the formation of 2-phenylethyl acetate in a transesterification reaction. The morphological properties of the materials were characterized using scanning electron microscopy, measurements of the surface area and pore size and volume, thermogravimetric analysis, and exploratory differential calorimetry. The results of the work indicate that the use of different silica precursors (TEOS or TMOS) and different drying techniques (aerogel or xerogel) can significantly affect the properties of the resulting biocatalyst. Drying with supercritical CO2 provided higher enzymatic activities and pore sizes and was therefore preferable to drying, using the xerogel technique. Thermogravimetric analysis and differential scanning calorimetry analyses revealed differences in behavior between the two biocatalyst preparations due to the compounds present.

Determination of the inclusion complex constant between oleuropein and cyclodextrins by complexation theory

Oleuropein (OLE) is a major phenolic compound of olive leaf (Olea europaea) and has many therapeutic properties associated with olive leaf extracts. This work concerns the determination of the inclusion complex constant between OLE and cyclodextrins (CDs), based on the competition of two guests for the CD cavity, one being a dye and the other OLE. The dye used was methylorange (MO) and pH 3 was selected, since MO molar absorptivity at 500xa0nm is at maximum in this condition. A solution of MO, OLE, and α-CD or β-CD, with citrate buffer was used for determining the absorbance values. From these data and by appropriate mathematical modeling, the equilibrium constant for the formation of OLE:CD complexes were obtained: for OLE:α-CD Kxa0=xa01,352.4xa0Lxa0mol−1 (R2xa0=xa00.9975) and for OLE:β-CD Kxa0=xa01,827.9xa0Lxa0mol−1 (R2xa0=xa00.9991). The results show that OLE has a greater affinity for β-CD than for α-CD and given the relatively high constants, OLE:CD complexes have potential for giving longer shelf lives for OLE medicinal and food additive preparations.