Resumo em Inglês:

Saccharomyces cerevisiae strain W303 was transformed with two yeast integrative plasmids containing Kluyveromyces lactis LAC4 and LAC12 genes that codify beta-galactosidase and lactose permease respectively. The BLR030 recombinant strain was selected due to its growth and beta-galactosidase production capacity. Different culture media based on deproteinized cheese whey (DCW) were tested and the best composition (containing DCW, supplemented with yeast extract 1 %, and peptone 3 % (w/v)) was chosen for bioreactor experiments. Batch, and fed-batch cultures with linear ascending feeding for 25 (FB25), 35 (FB35), and 50 (FB50) hours, were performed. FB35 and FB50 produced the highest beta-galactosidase specific activities (around 1,800 U/g cells), and also the best productivities (180 U/L.h). Results show the potential use of fed-batch cultures of recombinant S. cerevisiae on industrial applications using supplemented whey as substrate.

Resumo em Inglês:

The production of red pigments by Monascus ruber was evaluated utilizing complex culture media composed of glucose or sucrose (10 g/L), corn steep liquor (5 or 10 g/L) and monosodium glutamate (0, 5.0, 7.6, 11.4 or 15.2 g/L). Medium containing 10 g/L glucose, 5 g/L corn steep liquor and 7.6 g/L monosodium glutamate resulted the highest values of extracellular red pigment absorbance (20.7 U) and productivity (0.35 U/h). This medium also produced better results than using semi-synthetic medium with analytical grade reagents (12.4 U and 0.21 U/h). The cell growth was similar in both media (X <FONT FACE=Symbol>@</FONT> 6.5 g/L), indicating that the capacity of the cells to produce red pigments was higher in complex culture media. In addition, in the complex culture medium, less of the intracellular red pigments accumulated than in semi-synthetic medium (9.1% and 30%, respectively).

Resumo em Inglês:

Photocatalysis has been used as tertiary treatment for petroleum refinery wastewaters to comply with the regulatory discharge limits and to oxidize persistent compounds that had not been oxidized in the biological treatment. The wastewater is generated by the refinery and directly discharged into the Guanabara Bay (Rio de Janeiro). Although BOD removal is high, a residual and persistent COD, besides a somewhat high phenol content remains. Three photocatalysts were tested - TiO2 (Aldrich), ZnO (Aldrich), and TiO2 (P25, Degussa) - the third being the most active. The optimized conditions obtained with an experimental design were 3.0 g L-1 TiO2 and pH 6.3. The use of hydrogen peroxide (H2O2) showed no beneficial effect. Removal of 93% of phenols, 63% of dissolved organic carbon (DOC), and more than 50% of oil and grease (OG) were achieved in the photocatalytic process, improving the quality of the treated wastewater.

Resumo em Inglês:

This paper proposes a modification of ASM3 in a way that takes into account the process of production and consumption of microbial products (MPs) in a submerged membrane bioreactor fed with the effluent of a particular precoagulation sedimentation unit. A comparative representation of the modeling results obtained with ASM3 and ASM1 is performed and it highlights the importance of considering the process of storage of organic substrate, including MPs, as a prior step to bacterial growth. In addition to the suspended solids and microorganisms, various soluble organic substances, which might be either undecomposed organic substances contained in the raw water or MPs, are assumed to be selectively retained within the bioreactor. The results show that the carbonaceous materials are more accurately estimated by ASM3, while ASM1 performs slightly better than ASM3 in the estimation of nitrate. The estimated MP concentration in the mixed liquor and permeate agrees with the experimental evidence, and as expected, MPs play a role in supplying organic substrate to heterotrophs in both ASM1 and ASM3.

Resumo em Inglês:

The object of this work was to evaluate the capability of numerical simulation to predict different features of non-Newtonian fluid mixing process. A relatively simple impeller (six bladed vane rotor) was used for the mixing of carboxymethyl cellulose. A LDA method was used to measure the tangential velocity at two points inside the mixing vessel. Using visualization, a significant vortex above the impeller was observed. The shape of the free surface was determined by a geometrical reconstruction of the images of the illuminated section. Torque on the impeller shaft was measured to determine the characteristics of the fluid. Fluent program package was used for the simulation. The problem is challenging since the effects of non-Newtonian fluid, mixing process and free surface have to be included in the simulation. The comparison between the experimental and numerical results confirms the accuracy of the simulations.

Resumo em Inglês:

The gas-solids flow in a CFB riser is simulated applying two-fluid modeling. Two different procedures are used for the calculation of the solids phase pressure and stress tensor: the traditional procedure and an algebraic version of the kinetic theory of granular flows. Three different numerical meshes and two different discretization schemes for the advective terms are used. Results are compared to available experimental data from the literature. The effects of the solids phase modeling procedure, advection discretization scheme, and mesh size are discussed.

Resumo em Inglês:

This work presents an experimental study of a continuous gas-solid fluidized bed with an immersed horizontal tube. Silica sand (254mm diameter) was used as solid particles and air was used for fluidization in a 900mm long and 150mm wide heat exchanger. Measurements were made under steady state conditions for a solid particle mass flow rate from 14 to 95kg.h-1 and a number of baffles from 0 to 8. Results showed that the heat transfer coefficient increases with the solid particle mass flow rate and with the number of baffles, suggesting that these are important factors to be considered in the design of such equipment. An empirical correlation for the heat transfer coefficient is proposed as a function of solid particle and gas mass flow rate, number of baffles and gas velocity.

Resumo em Inglês:

Aureobasidium pullulans is a microorganism that produces pullulan (homopolysaccharide) extracellularly through a fermentation process with sugars (maltose, d-xylose, sucrose and starch) as its carbon source. Pullulan is a linear polysaccharide of D-glycopyranose containing (1 ->4)-alpha and (1 -> 6)-alpha linkages at a 2:1 ratio, is highly soluble in water and has various applications in the food, packaging, film and pharmaceutical industries. Lipids, primarily oils, having antifoaming properties as well as nutritional particularities, are considered an essential additional carbon source for the growth of microorganisms, especially fungi. These nutrient sources are very important for the maintenance of microorganism cells. In fact, these positive effects are only achieved when the right source is added at both the right time and the right dosage into the broth of the fermentation process. In this research on pullulan production with the strains NRRL Y-6220 and NRRL Y-2311-1, it was found that the latter strain achieved better results for undesirable pigment formation, pullulan titer, time of maximum production (96 hours) and biomass yields than strain NRRL Y-6220, which also showed suitable results for biomass yields and cell morphology. However, the dark pigmentation of the strain NRRL Y-6220, formed through the process, makes its application unacceptable for foods and pharmaceuticals. Strain NRRL Y-2311-1 was shown to be a promising potential industrial microorganism, whose applications should be studied more in depth.

Resumo em Inglês:

The influence of molybdenum oxide as a promoter on the V2O5/Nb2O5 system was investigated. A series of MoO3/V2O5/Nb2 O5 catalysts, with MoO3 loading ranging from 1 to 3 wt% MoO3 and fixed V2O5 content (21 wt%), were prepared by impregnation of the Nb2O5 support with an aqueous solution of ammonium metavanadate and ammonium molybdate. The acid-base properties of the catalysts were investigated to determine of the selectivity of the isopropanol decomposition reaction. The X-ray diffraction results showed the presence of the beta-(Nb,V)2O5 phase. The temperature-programmed reduction profiles showed that the reducibility of vanadium was affected by the presence of molybdenum oxide. Activity results for isopropanol decomposition revealed that the acid-base properties of V2O5/Nb2O5 catalysts are affected upon incorporation of MoO3, specifically for loadings of 3 wt %. For this catalyst composition both propylene and acetone formation rates decreased.

Resumo em Inglês:

This work describes the conditions for selective extraction of the alkaloids in Andreadoxa flava (Kallunki). The experiments were performed in a pilot plant SFE 500, in the following conditions. Extractor pressures 206.8 x 10(5), 241.3 x 10(5), 275.8 x 10(5) and 310.3 x 10(5) Pascal and pressures of 137.9 x 10(5), 69.0 x 10(5) and 55.2 x 10(5) Pascal for separators 6, 7 and 8 respectively. The temperatures were 40 °C in the extractor and 20 ºC in the separators. The samples, extracted from A. flava leaves, were analysed by ¹H NMR and GC/FID as well as by comparison with standards. This procedure allowed the identification for the first time of the 2-quinolone alkaloid 8-methoxy-N-methyl-flindersine in A. flava leaves of the. In addition, zanthophylline, 5-methoxyalmene and 8-methoxyflindersine were identified as the main alkaloids in leaves. Under the best conditions for zanthophylline extraction it was possible to obtain a purity of 79.4% while with other phytochemical technique 55.5% was obtained.

Resumo em Inglês:

The thermal decomposition in argon of the monohydrated ammonium tris(oxalate)niobate, (NH4)3NbO(C2O4)3.H 2O, has been studied by TG/DTG, DTA, DSC, IR absorption and XRD. The material decomposes stepwise by the release of CO, CO2, NH3 and water. The atomic structure of the complex initially becomes amorphous and then crystallizes twice in the form of orthorhombic and monoclinic niobium pentoxide.

Resumo em Inglês:

A nonequilibrium heat and mass transfer model is presented for the steady-state operation of a rectifying column, employed in ammonia-water absorption refrigeration systems to dehumidify the ammonia vapor leaving the generator. The thermodynamic state relations of the mixture are derived from two equations representing the Gibbs free energy in terms of temperature, pressure and concentration for the liquid and the vapor phases. Two of the transport properties, surface tension and liquid diffusivity required original relations, as presented here in. The resulting nonlinear system of equations is solved by efficient use of the Newton-Raphson code that minimizes the order of the Jacobian matrix without losing any model information or the quadratic order of convergence of the numerical method. Accuracy tests are performed by grid refinement and by comparison with results in the literature. A sensitivity study is presented showing the influence of some alternative methods for estimation of the transport properties on the temperature and concentration profiles.

Resumo em Inglês:

This paper presents experimental results for adsorption equilibrium of methane, ethane, and butane on nanoporous activated carbon obtained from coconut shells. The adsorption data were obtained gravimetrically at temperatures between 260 and 300K and pressures up to 1 bar. The Toth isotherm was used to correlate the data, showing good agreement with measured values. Low-coverage equilibrium constants were estimated using virial plots. Heats of adsorption at different loadings were also estimated from the equilibrium data. Adsorption properties for this material are compared to the same properties for BPL activated carbon and BAX activated carbon.