Resumo em Inglês:

In 1990, the Biotechnology and the Control Systems Groups of IPT started developing a system for the control and automation of fermentation processes, applied to the oxidation of sorbitol to sorbose by the bacteria Gluconobacter oxydans, the microbial step of the vitamin C production process, that was chosen as a case study. Initially, a thirteen-parameter model was fitted to represent the batch operation of the system utilizing a nonlinear regression analysis, the flexible polyhedron method. Based on these results, a model for the continuous process (with the same kinetic equations) was constructed and its optimum operating point obtained

Resumo em Inglês:

The removal of phosphate in an up-flow anaerobic sludge blanket (UASB) reactor treating a synthetic substrate simulating domestic sewage and its relation with the presence of FeCl3 in the influent was investigated. Phosphate removal efficiencies were 30%, 54% and 84% for influent FeCl3 concentrations of 90 mg.L-1 and 200 mg.L-1, respectively. Scanning eletronic microscopy of granular sludge samples taken from the reactor showed the presence of Methanothrix- like microorganisms as the main predominant methanogenic bacteria. Iron precipitates such as vivianite [Fe3(PO4)2 . 8 H2O] were identified in granular samples by x-ray defraction and energy dispersion x-ray (EDX) analyses

Resumo em Inglês:

The immobilization of <FONT FACE="Symbol">b</font> -galactosidase from Kluyveromyces fragilis on controlled pore silica was investigated. Immobilization was performed on amino silica activated with glutaraldehyde and the product was applied to the hydrolysis of lactose of whey. The behaviors of the soluble and immobilized enzyme were compared by using whey and a lactose solution as the substrate. With the aim of optimizing the method, parameters such as the amount of glutaraldehyde and the size of the particles were evaluated by comparing activities and stabilities on batch and continuously fluidized bed reactors

Resumo em Inglês:

The production of penicillin G by Penicillium chrysogenum IFO 8644 was simulated employing a feedforward neural network with three layers. The neural network training procedure used an algorithm combining two procedures: random search and backpropagation. The results of this approach were very promising, and it was observed that the neural network was able to accurately describe the nonlinear behavior of the process. Besides, the results showed that this technique can be successfully applied to control process algorithms due to its long processing time and its flexibility in the incorporation of new data

Resumo em Inglês:

Multi-point immobilization, by an intense enzyme-support attachment, may increase the operational stability of a biocatalyst. Penicillin G acylase has many applications, from the hydrolysis of penicillin G (production of 6-aminopenicillanic acid) to the synthesis of semi-synthetic antibiotics. The application of this technique in macroporous silica involves support activation with 3-glycidyloxypropyltrimetoxysilane, followed by acidic hydrolysis and oxidation with sodium periodate. The aldehyde-glyoxyl groups so formed react subsequently with the enzyme. The degree of activation affects the yield and stability of the enzyme immobilization. For 20 UI of enzyme, the results show an immobilization yield equal to 100%, whenever there are more than 140 <FONT FACE="Symbol">m</FONT> Eq of aldehyde groups/g of dry silica. The immobilized enzyme half-life is 23 minutes at 60ºC; under the same conditions, the soluble enzyme has no residual activity after a few minutes. The increase in the degree of activation does not lead to higher stability, which indicates the negative influence of sub-products, formed during the activation of the support

Resumo em Inglês:

In this work, a bidisperse model is built to represent the hydrolysis of maltose using immobilized glucoamylase. The experimental set is a mixed-batch reactor, maintained at 30ºC, with pectin gel spherical particles that contain enzyme immobilized in macroporous silica. The possibility of substrate adsorption on the pectin gel is also studied because this phenomenon may result in smaller values of diffusivity. Equilibrium assays are then performed for different substrates (maltose, lactose and glucose) at different temperatures and pHs. These assays show that adsorption on the pectin gel is not important for the three dextrins analysed. The bidisperse model presents a good fit with the experimental data, when using previously-estimated kinetic and mass transfer parameters (Gonçalves et al., 1997). This result shows that the methodology used (wrapping the silica in pectin gel) is appropriate for experimental studies with silica, since it allows a higher degree of agitation without causing shearing

Resumo em Inglês:

In this work the effects of diffusion on the hydrolysis of maltose using glucoamylase immobilized on macroporous silica at 30o C are studied. Two different kinds of experimental assays are carried out: one using free enzyme and the other using an enzyme covalently linked to macroporous silica, preactivated with glutaraldehyde. Free enzyme assays are used to estimate the kinetic parameters for hydrolysis of maltose at 30ºC, according to a Michaelis-Menten equation, with inhibition by the product. Runs with the immobilized enzyme enable us to estimate dextrin diffusivities in silica, assuming that the inherent kinetic parameters are equal to the intrinsic ones. The values of kinetic and mass transfer parameters are: K3 = 0.90x10-5 g/U.s, Km = 0.61x10-3 g/ml, Ki = 1.23x10-1 g/ml, DMs = 0.50x10-6 cm2 /s and DGs = 0.55x10-6 cm2 /s

Resumo em Inglês:

This paper presents an enzymatic process for sorbitol and gluconic acid production using cells of Zymomonas mobilis permeabilized with CTAB. Equimolar solutions of glucose and fructose (from 96.0 to 422.2 g/L) were used. In a batch reactor, conversions of 97% were attained after 15 to 20 hours of reaction. The effect of the initial concentration of the substrates was evaluated in experiments using 20% more and 20% less glucose than fructose. It was observed that the reaction performed with more fructose reached completion faster and with a higher value of conversion

Resumo em Inglês:

Two control algorithms were implemented in the stabilization of the dissolved oxygen concentration of the penicillin process production phase. A deterministic and nonstructured mathematical model was used, where were considered the balances of cell, substrate, dissolved oxygen and product formation as well as kinetic of the growth, respiration, product inhibition due to excess of substrate, penicillin hydrolyze, yield factors among cell growth, substrate consumption and dissolved oxygen consumption. The bioreactor was operated in a feed-batch way using an optimal strategy for the operational policy. The agitation speed was used as manipulated variable in order to achieve the dissolved oxygen control because it was found to be the most sensitive one. Two types of control configurations were implemented. First, the PID feedback control with the parameters estimated through Modified Simplex optimization method using the IAE index, and second, the DMC predictive control that had as control parameters the model, prediction and control horizons as well as suppression factor and the trajectory parameter. A sensitivity analysis of these two control algorithms was performed using the sample time and dead time as the index to make stability evaluation. Both configurations showed stable performance, however, the predictive one was found to be more robust in relation to the sample time, as well as the dead time variations. This is a very important characteristic to be considered for the implementation of control scheme in real fermentative process

Resumo em Inglês:

The present work describes the development and operation of a continuous rotational impeller rheometer for on-line rheological measurements in fermentation broths. In an initial step three devices were calibrated, two of them utilizing helical ribbon impellers and the third a six-bladed impeller. The calibration constants obtained were within the range mentioned in the literature, showing consistency with the methodology employed. In the sequence, the system with one of the helical ribbon impellers (HR39) was selected for on-line continuous rheological measurements due to its small dimensions and its wide measurement range. Finally, the performance of the proposed device, in terms of rheological measurements in Aspergillus awamori broths, was compared to that of a commercial bench rheometer. The comparison of on-line and off-line rheological measurements showed a good agreement between both measurement techniques. Furthermore, results suggest that the proposed on-line rheometer features higher sensitivity and easier operation than the commercial rheometer

Resumo em Inglês:

The self-assembly technique is employed for producing alternating ultra-thin films of lysozyme and poly(styrene sulfonate) (PSS). The influence of important parameters in the self-assembly process, namely immersion time, drying method, solution pH and ionic strength, on adsorption kinetics is investigated by ultraviolet (UV) spectroscopy. The absorbance increases rapidly in the initial stages of adsorption for all pHs studied, before reaching a plateau indicative of complete adsorption. Adsorption is considerably more effective when the proton concentration in the solution increases, which is attributed to the increase in the positive charge density within the protein molecules. Furthermore, UV absorbance increases linearly with the number of bilayers (lysozyme/PSS), indicating that a constant amount of material is being adsorbed at each deposition process. These results are highly promising as the self-assembled films are of great interest for biotechnology and molecular electronic applications

Resumo em Inglês:

A fed-batch alcohol fermentation on a pilot plant scale with a digital supervisory control system was evaluated as an experimental application case study of an adaptive controller. The verification of intrinsically dynamic variations in the characteristics of the fermentation, observed in previous work, showed the necessity of an adaptive control strategy for controller parameter tuning in order to adjust the changes in the specific rates of consumption, growth and product formation during the process. Satisfactory experimental results were obtained for set-point variations and sugar feed concentration load changes in the manipulated inlet flow to the fermenter

Resumo em Inglês:

Enzymatic sensors for the continuous measurement of glucose and sucrose, with the use of an enzymatic microreactor and a continuous flow dilution line for the medium, are studied in this work. The effects of the best conditions for medium and sampling flow through the sensor were analysed for a glucose concentration range from 0.05 to 0.2 g/l , which was possible to extend to a range from 5.0 to 120 g/l using a dilution and sampling circuit with the FIA analysis methodology

Resumo em Inglês:

The aim of this work was to study the influence of phosphate concentrations on glucoamylase production by the fungus Aspergillus awamori. In culture media containing cassava flour, different levels of phosphates were tested and the fungal responses to increasing levels (whether or not coupled to pH adjustment throughout the run) were assessed in terms of the resulting glucoamylase production. Phosphate increments, associated with pH readjustments throughout the run, yielded around 1,200 U/L of quite stable glucoamylase activity in the broth, while under a conventional condition (low phosphate without pH readjustment), enzymatic activity was around 350 U/L, which decayed dramatically towards the end of the cultivation

Resumo em Inglês:

The anaerobic treatment processes are considered to be well-established methods for the elimination of easily biodegradable organic matter from wastewaters. Some difficulties concerning certain wastewaters are related to the possible presence of dissolved oxygen. The common belief is that anaerobes are oxygen intolerant. Therefore, the common practice is to use sequencing anaerobic and aerobic steps in separate tanks. Enhanced treatment by polishing off the residual biodegradable oxygen demand from effluents of anaerobic reactors, or the biodegradation of recalcitrant wastewater pollutants, usually requires sequenced anaerobic and aerobic bacteria activities. However, the combined activity of both bacteria can also be obtained in a single reactor. Previous experiments with either pure or mixed cultures showed that anaerobes can tolerate oxygen to a certain extent. The oxygen toxicity to methanogens in anaerobic sludges was quantified in batch experiments, as well as in anaerobic reactors. The results showed that methanogens have a high tolerance to oxygen. In practice, it was confirmed that dissolved oxygen does not constitute any detrimental effect on reactor treatment performance. This means that the coexistence of anaerobic and aerobic bacteria in one single reactor is feasible and increases the potentials of new applications in wastewater treatment

Resumo em Inglês:

Modern high-rate anaerobic wastewater treatment processes are rapidly becoming popular for industrial wastewater treatment. However, until recently stable process conditions could not be guaranteed for alcoholic wastewaters containing higher concentrations of methanol. Although methanol can be directly converted into methane by methanogens, under specific conditions it can also be converted into acetate and butyrate by acetogens. The accumulation of volatile fatty acids can lead to reactor instability in a weakly buffered reactor. Since this process was insufficiently understood, the application of high-rate anaerobic reactors was highly questionable. This research investigated the environmental factors that are of importance in the predominance of methylotrophic methanogens over acetogens in a natural mixed culture during anaerobic wastewater treatment in upflow anaerobic sludge bed reactors. Technological and microbiological aspects were investigated. Additionally, the route by which methanol is converted into methane is also presented

Resumo em Inglês:

The yield coefficient Yx/s was correlated with variables such as temperature (22.8-29.2 oC), concentrations of corn steep liquor (6.4-57.4 g/L), ammonium sulfate (5.6-18.4 g/L), sucrose (4.0-36.0 g/L) and soybean oil (3.0-7.0 g/L), all important variables in the growth stage of the Penicillium chrysogenum fungus. An empirical model was obtained by response surface statistical experimental design. The tests were performed with a complex culture medium in a rotatory shaker. The highest Yx/s values were obtained at low sucrose concentrations (~4.0 g/L) and high corn steep liquor concentrations (~57.4 g/L). Temperature, ammonium sulfate and soybean oil concentrations showed no significant effect on Yx/s

Resumo em Inglês:

A dynamic mathematical model, simulation and computer control of a Continuous Affinity Recycle Extraction (CARE) process, a protein purification technique based on protein adsorption on solid-phase adsorbents is described in this work. This process, consisting of three reactors, is a multivariable process with considerable time delay in the on-line analyses of the controlled variable. An advanced predictive control configuration, specifically the Dynamic Matrix Control (DMC), was applied. The DMC algorithm was applied in process schemes where the aim was to maintain constant the enzyme concentration in the outlet of the third reactor. The performance of the DMC controller was analyzed in the feed-flow disturbances and the results are presented.