Resumo em Inglês:

This work presents an age-structured population balance model (ASPBM) for a bioprocess in a continuous stirred-tank fermentor. It relates the macroscopic properties and dynamic behavior of biomass to the operational parameters and microscopic properties of cells. Population dynamics is governed by two time- and age-dependent density functions for living and dead cells, accounting for the influence of substrate and dissolved oxygen concentrations on cell division, aging and death processes. The ASPBM described biomass and substrate oscillations in aerobic continuous cultures as experimentally observed. It is noteworthy that a small data set consisting of nonsegregated measurements was sufficient to adjust a complex segregated mathematical model.

Resumo em Inglês:

Whey is an abundant effluent in the production of cheese and casein. The biotechnological utilization of this economically important and nutritive source is limited mainly because of the presence of high percentages of lactose. This disaccharide has poor solubility, which can cause crystallization and insufficient sweetness in dairy food; additionally, part of the adult population suffers from associated lactose intolerance diseases. There are several methods to determine lactose such as spectrophotometry, polarimetry, infrared spectroscopy, titrimetry and chromatography. However these methods are tedious and time-consuming due to long sample preparation. These disadvantages stimulated the development of an enzymatic lactose biosensor. It employs two immobilized enzymes, beta-galactosidase and glucose oxidase and the quantitative analysis of lactose is based on determination of oxygen consumption in the enzymatic reaction. The influence of temperature on the biosensor signal was experimentally studied. It was observed that a nonlinear relationship exists between the electric response of the biosensor - provided by CAFCA (Computer Assisted Flow Control & Analysis - ANASYSCON, Hannover) - and lactose concentration. In this work, attempts were made to correlate these variables using a simple nonlinear model and multilayered neural networks, with the latter providing the best modeling of the experimental data.

Resumo em Inglês:

Two receptor-binding sites for hGM-CSF are described. Competitive binding ELISA using four monoclonal antibodies (MAbs) showed different epitope recognitions. The antibody combining sites were mapped using sets of overlapping peptides and hexapeptide libraries prepared by the SPOT synthesis technique. We identified the conformationally dependent epitopes A18E21R23R24F119 and R23E21N17W13 bound by MAb CC5B5 and the nonlinear epitope P118F119W13E14 bound by MAb M1B8. The epitopes recognized by these two MAbs are very closely located on the native protein surface. The peptide L61YKQGKLRGSLTK72 was recognized by MAb M7E10 and the peptide A1PAR4, representing the N-terminal sequence of the protein, was bound by the nonneutralizing MAb CC1H7. Inhibition assays of the GM-CSF biological activity demonstrated that MAb M1B8, CC5B5 and M7E10 bind to domains which are responsible for the interaction of the cytokine with the GM-CSF receptor.

Resumo em Inglês:

Two groups of isoforms of rhEPO, at a concentration of 300 µg/ml, were tested as putative inhibitors of the lectinic hemagglutination reaction in order to obtain affinity ligand(s) for hormone purification: groups I (pI: 3.80; 3.89; 3.95; 4.07, 4.15 and 4.26) and groups II (pI: 4.15, 4.26; 4.38; 4.51; 4.72 and 4.93) Crude extracts from the vegetable materials Abrus precatorious (Abrin), Artocarpus incisa (Frutalin), Artocarpus integrifolia (Jacalin), Canavalia ensiformes (ConA), Canavalia brasiliensis (Conbr), Cratylia floribunda, Dioclea altissima (DAL), Dioclea grandiflora (DGL), Erythrina vellutina (EVL), Erythrina cristagalli, Lutaelburgia auriculata (lectin not fully characterized yet), Lycopersicum esculentum (LEA), Phaseolus vulgaris (PHA), Ricinus communis (Ricin) and Triticum vulgaris (WGA) were used. Only some of the galactose-specific lectins and the GlcNAc-specific lectins showed rapid full inhibition of the hemagglutination reaction for the less acidic isoforms and the total isoforms of rhEPO, respectively. On this basis, the selected lectins were purified by affinity chromatoghraphy and covalently coupled to cyanogen bromide activated Sepharose® (Amersham-Pharmacia). CHO.K1 cell culture supernatant containing rhEPO was loaded onto the lectin resins and the recoveries were calculated by using specific elutions.

Resumo em Inglês:

High-performance affinity matrices were obtained by attaching pseudobiospecific ligands to hollow-fibre membranes. The neutral protease contained in FlavourzymeTM was purified to homogeneity with Yellow 4R-HE affinity hollow-fibre membranes. Immobilisation of Red HE-3B allowed purification of a milk-clotting enzyme obtained by solid-state culture of Mucor bacilliformis. Copper immobilisation through iminodiacetic acid allowed fractionation of Biocon Bioconcentrated PlusTM to separate the pectinesterase-containing fraction. The productivity of the developed processes - 1900, 94 and 750 U/ml.min, respectively - was 10- to 15-fold higher than that achieved with the same ligands immobilised on agarose-based soft gels, mainly due to the shortening of the purification processes.

Resumo em Inglês:

A process of directed evolution applied to obtain a library of mutants of horseradish peroxidase (HRP) enzyme is described. We have introduced slight variations into the original DNA shuffling protocol. A DNA template was prepared by PCR amplification and digested with Dnase I during 1 hour. Dnase I products were concentrated by precipitation with isopropanol. Gel electrophoresis showed fragments of the desired size range (20-600 pb) without a full-length template remaining in the reaction mixture. A high concentration of fragments was crucial for performing PCR without primers. In this case, a template concentration of 32.5 ng/mu l was appropriate. Amplification of recombinant genes in a standard PCR reaction (template dilution 1:100) produced a smear with a low yield for the full-length sequence. A single product of the correct size was obtained by PCR with nested primers separated from the previously used primers by 40 pb. In our laboratory, native HRP has been functionally expressed in a baculovirus expression vector system. The purpose is to develop the screening of the first generation of random mutants in this system. To facilitate detection of those clones that have high peroxidase activity, we developed a rapid method: after five days postinfection agarose plates with six wells were covered with DAB (3,3´-diaminobenzidine) and H2O2. The appearance of brown-black stain allows visualization of up to 100 active clones/well in only 1 min.

Resumo em Inglês:

The objective of this work is to electronically analyze toluene adsorption reactions on VSbO4(110). Thus, perpendicular and parallel toluene interactions on the different active sites of the oxide surface (O, Sb and V ions) were studied. Adsorption energy was calculated using the ASED-MO theory, while the electronic analysis was performed with the YAEHMOP code. The electronic density of states (DOS) of the VSbO4 cluster, modeled with a trirutile-type tetragonal supercell, resembles that of 3D solids with a rutile structure. However, due to the presence of vanadium, small peaks appear above the Fermi level. The DOS of toluene has several peaks resulting from the interaction of the aromatic ring with the methyl fragment, which changes when the adsorbate interacts with the oxide surface. The C-H bonds in the methyl fragment as well as the Cmethyl-Cphenyl bond weaken when some electronic density is removed. Also, hydrocarbon oxidation could weaken the p system of the aromatic ring. For toluene perpendicular adsorption (on the V site) the calculations show a hybridization of those orbitals coming from the methyl fragment and the phenyl-methyl interaction energy region. After toluene parallel adsorption on Sb-V sites, the DOS shows an important broadening of some of the methyl and phenyl fragment orbitals. In addition, a study of the overlap population suggests that one of the H atoms of the methyl group can be abstracted with the participation of the Sb cation.

Resumo em Inglês:

In the present work, clays pillared with aluminium and impregnated with transition metals (Fe, Co and Cr) were prepared, characterised and studied as catalysts in the oxidation of chlorobenzene. The pillared clay was synthesised using a natural montmorillonite from San Juan (Argentina) as the starting material and an aluminium polycation solution. The catalysts were prepared by impregnating the pillared clay and then calcinating at 500ºC. The catalysts were characterised by XRD, temperature-programmed reduction (TPR) and nitrogen adsorption isotherms. The samples were tested in the deep oxidation of chlorobenzene in some cases reaching more than 90% of total conversion.

Resumo em Inglês:

The oxidation of propane on was studied with Pt-xWO3/Al2O3 catalysts was studied ,by varying the concentration of tungsten sublayer. Thermal analysis and XRD in situ showed that the enrichment of tungsten at the surface is associated with the formation of HxWO3 bronze. FTIR results with C3H8 and O2 indicated that the catalyst surface properties and the interaction between W and Pt were modified. These modified surface complexes prevented the formation of acetates and formate species. The addition of W increased the activity of Pt/Al2O3 towards in C3H8 oxidation. Tungsten was the main responsible for the stability of the bimetallic catalysts in the presence of water.

Resumo em Inglês:

During the last decade, nonthermal plasma technology was applied in many different fields, focusing attention on the destruction of harmful compounds in the air. This paper deals with nonthermal plasma reactors for the conversion of heavy oil into light hydrocarbon olefins, to be employed as gasoline components or to be added in small amounts for the catalytic reduction of nitrogen oxide compounds in the treatment of exhaust gas at power plants. For the process, the plate-plate nonthermal plasma reactor driven by AC high voltage was selected. The reactor was modeled as a function of parameter characteristics, using the methodology provided by the statistical experimental design. The parameters studied were gap distance between electrodes, carrier gas flow and applied power. Results indicate that the reactions occurring in the process of heavy oil conversion have an important selective behavior. The products obtained were C1-C4 hydrocarbons with ethylene as the main compound. Operating the parameters of the reactor within the established operative window of the system and close to the optimum conditions, efficiencies as high as 70 (mul/joule) were obtained. These values validate the process as an in-situ method to produce light olefins for the treatment of nitrogen oxides in the exhaust gas from diesel engines.

Resumo em Inglês:

The production of large quantities of paint sludge is a serious environmental problem. This work evaluates the use of pyrolysis reaction as a process for deactivating paint sludge that generates a combustible gas phase, a solvent liquid phase and an inert solid phase. These wastes were classified into three types: water-based solvent (latex resin) and solvents based on their resins (alkyd and polyurethane). An electrically heated stainless steel batch reactor with a capacity of 579 mL and a maximum pressure of 30 atm was used. Following the reactor, a flash separator, which was operated at atmospheric pressure, partially condensed and separated liquid and gas products. Pressure and temperature were monitored on-line by a control and data acquisition system, which adjusted the heating power supplied to the pyrolysis reactor. Reactions followed an experimental design with two factors (reaction time and temperature) and three levels (10, 50 and 90 minutes; 450, 550 and 650°C). The response variables were liquid and solid masses and net heat of combustion. The optimal operational range for the pyrolysis process was obtained for each response variable. A significant reduction in total mass of solid waste was obtained.

Resumo em Inglês:

The microbial reduction of chromium(VI) to chromium(III) has been one of the most widely studied forms of metal bioremediation. Recently, we have found that Thiobacillus ferrooxidans and Thiobacillus thiooxidans, growing on elemental sulphur, can indirectly promote chromium(VI) reduction by producing reducing agents such as sulphite and thiosulphate, which abiotically reduce chromium(VI). Those species of Thiobacillus are acidophilic bacteria which grow optimally at pH values lower than 4. However, most of those reducing agents are stabilised at higher pH values. Thus, the present paper reports on the ability to reduce chromium(VI) using another specie of Thiobacilli, Thiobacillus thioparus, which is able to grow at pH close to 7.0. T. thioparus cultures were carried out in a fermentation vessel containing medium and sulphur as the sole energy source and maintained at 30ºC and 400 rpm. The pH was adjusted to 6.0, 7.0 or 8.0 and maintained with the automatic addition of KOH. Our results show high chromium (VI) reduction values (close to 100% at the end of bacterial growth) at the three pH values. The results of these experiments are very promising for development of a microbiological process to be used in the detoxification of chromium(VI)-polluted effluents.

Resumo em Inglês:

The emission of CO2 from power plants that burn fossil fuels is the major cause of the accumulation of CO2 in the atmosphere. The separation of CO2 from CO2/air mixtures can play a key role in alleviating this problem. This separation can be carried out by using suitable adsorbents, such as carbon molecular sieves. In this work, a CMS was prepared by deposition of polyfurfuryl alcohol polymer on activated carbon. After deposition of the polymer, the material was carbonized at 800ºC for 2 hours. This material was used to separate O2/N2 mixtures and CO2 in a fixed bed at room temperature. Experimental breakthrough curves obtained were fitted to theoretical models in order to establish the main mechanisms of mass transfer. The breakthrough curves showed that it is possible to separate O2, N2 and CO2. The shape of the breakthrough curves was not influenced by the total flow, indicating that the gas contact for the gas mixture was good. The experimental data were fitted to theoretical models and it was established that the main mechanism of mass transfer was intraparticle diffusion.

Resumo em Inglês:

The objective of this work is to analyze the possibility of applying the drying curves generalization methodology to the conductive/convective hot plate drying of cellulose. The experiments were carried out at different heated plate temperatures and air velocities over the surface of the samples. This kind of approach is very interesting because it permits comparison of the results of different experiments by reducing them to only one set, which can be divided into two groups: the generalized drying curves and the generalized drying rate curves. The experimental apparatus is an attempt to reproduce the operational conditions of conventional paper dryers (ratio of paper/air movement) and consists of a metallic box heated by a thermostatic bath containing an upper surface on which the cellulose samples are placed. Sample material is short- and long-fiber cellulose sheets, about 1 mm thick, and ambient air was introduced into the system by a adjustable blower under different conditions. Long-fiber cellulose generalized curves were obtained and analyzed first individually and then together with the short-fiber cellulose results from Motta Lima et al. (2000 a,b). Finally, a set of equations to fit the generalized curves obtained was proposed and discussed.