Francisco Maugeri Filho

Mathematical modeling and simulation of inulinase adsorption in expanded bed column

A mathematical model for an expanded bed column was developed to predict breakthrough curves for inulinase adsorption on Streamline SP ion-exchange adsorbent, using a crude fermentative broth with cells as the feedstock. The kinetics and mass transfer parameters were estimated using the PSO (particle swarm optimization) heuristic algorithm. The parameters were estimated for each expansion degree (ED) using three breakthrough curves at initial inulinase concentrations of 65.6UmL(-1). In sequence, the model parameters for an ED of 2.5 were validated using the breakthrough curve at an initial concentration of 114.4UmL(-1). The applicability of the validated model in process optimization was investigated, using the model as a process simulator and experimental design methodology to optimize the column and process efficiencies. The results demonstrated the usefulness of this methodology for expanded bed adsorption processes.

Kinetics of ethanol production from sugarcane bagasse enzymatic hydrolysate concentrated with molasses under cell recycle

In this work, a kinetic model for ethanol fermentation from sugarcane bagasse enzymatic hydrolysate concentrated with molasses was developed. A model previously developed for fermentation of pure molasses was modified by the inclusion of a new term for acetic acid inhibition on microorganism growth rate and the kinetic parameters were estimated as functions of temperature. The influence of the hydrolysate on the kinetic parameters is analyzed by comparing with the parameters from fermentation of pure molasses. The impact of cells recycling in the kinetic parameters is also evaluated, as well as on the ethanol yield and productivity. The model developed described accurately most of the fermentations performed in several successive batches for temperatures from 30 to 38°C.

An alternative process for butanol production: Continuous flash fermentation

The objective of this work is to introduce and demonstrate the technical feasibility of the continuous flash fermentation for the production of butanol. The evaluation was carried out through mathematical modeling and computer simulation which is a good approach in such a process development stage. The process consists of three interconnected units, as follows: the fermentor, the cell retention system (tangential microfiltration) and the vacuum flash vessel (responsible for the continuous recovery of butanol from the broth). The efficiency of this process was experimentally validated for the ethanol fermentation, whose main results are also shown. With the proposed design the concentration of butanol in the fermentor was lowered from 11.3 to 7.8 g/l, which represented a significant reduction in the inhibitory effect. As a result, the final concentration of butanol was 28.2 g/l for a broth with 140 g/l of glucose. Solvents productivity and yield were, respectively, 11.7 g/l.h and 33.5 % for a sugar conversion of 95.6 %. Positive aspects about the flash fermentation process are the solvents productivity, the use of concentrated sugar solution and the final butanol concentration. The last two features can be responsible for a meaningful reduction in the distillation costs and result in environmental benefits due to lower quantities of wastewater generated by the process.

Inulinase production in a batch bioreactor using agroindustrial residues as the substrate: experimental data and modeling.

The production of inulinase employing agroindustrial residues as the substrate is a good alternative to reduce production costs and to minimize the environmental impact of disposing these residues in the environment. This study focused on the use of a phenomenological model and an artificial neural network (ANN) to simulate the inulinase production during the batch cultivation of the yeast Kluyveromyces marxianus NRRL Y-7571, employing a medium containing agroindustrial residues such as molasses, corn steep liquor and yeast extract. It was concluded that due to the complexity of the medium composition it was rather difficult to use a phenomenological model with sufficient accuracy. For this reason, an alternative and more cost-effective methodology based on ANN was adopted. The predictive capacity of the ANN was superior to that of the phenomenological model, indicating that the neural network approach could be used as an alternative in the predictive modeling of complex batch cultivations.

Optimization Strategies Based on Sequential Quadratic Programming Applied for a Fermentation Process for Butanol Production

In this work, the mathematical optimization of a continuous flash fermentation process for the production of biobutanol was studied. The process consists of three interconnected units, as follows: fermentor, cell-retention system (tangential microfiltration), and vacuum flash vessel (responsible for the continuous recovery of butanol from the broth). The objective of the optimization was to maximize butanol productivity for a desired substrate conversion. Two strategies were compared for the optimization of the process. In one of them, the process was represented by a deterministic model with kinetic parameters determined experimentally and, in the other, by a statistical model obtained using the factorial design technique combined with simulation. For both strategies, the problem was written as a nonlinear programming problem and was solved with the sequential quadratic programming technique. The results showed that despite the very similar solutions obtained with both strategies, the problems found with the strategy using the deterministic model, such as lack of convergence and high computational time, make the use of the optimization strategy with the statistical model, which showed to be robust and fast, more suitable for the flash fermentation process, being recommended for real-time applications coupling optimization and control.

Purification of fructooligosaccharides in an activated charcoal fixed bed column.

Fructooligosaccharides (FOS) are mixtures of oligosaccharides containing mono and disaccharides, therefore, the separation of these sugars results in purer products for human consumption and can be added to various food products (drinks, cookies and yogurt). The aim of this work was the purification of fructooligosaccharides from a mixture of sugars, obtained by enzymatic synthesis, containing fructooligosaccharides, glucose, fructose and sucrose using activated charcoal fixed bed column. Temperature and ethanol concentration effects were analyzed using a 2² central composite design. Good separation conditions were obtained through central composite design. The best separation coefficient between fructooligosaccharides and glucose (ES(fructoolig/gluc)) was 3.99 ± 0.07 and between fructose and fructooligosaccharides (ES(fructoolig/fruct)) was 2.89 ± 0.36 using ethanol 15% (v/v) as eluent, at 50°C. The final FOS purification degree and recovery were about 80% and 97.8%, respectively. The activated charcoal fixed bed columns were shown to be a good alternative for sugar separation, especially for rich mixtures of fructooligosaccharides.

Dynamics of a continuous flash fermentation for butanol production

University of Campinas, UNICAMP School of Chemical Engineering, P.O. Box 6066, 13083-970 Campinas SP

Kinetic studies and modelling of the production of fructooligosaccharides by fructosyltransferase from Rhodotorula sp

Fructosyltransferase was produced by a strain of Rhodotorula, isolated from flowers collected in the costal Atlantic Forest located in Southern Brazil and screened according to its ability to produce the enzyme. The production was carried out in submerged fermentation and subsequently purified using the following three procedures: alcohol precipitation, Q-Sepharose ion-exchange chromatography and ultrafiltration. The studies of fructooligossacaride production were carried out in a batch stirred reactor using sucrose as the substrate and 5 UTF mL−1 of fructosyltransferase at pH 4.5 and 50 °C. Since the industrial application of this enzyme does not require a highly purified enzymatic solution, the enzyme kinetics were comparatively performed using both partially purified (only alcohol precipitated enzyme) and purified (using all steps specified above) enzyme. The kinetics showed a characteristic Michaelis–Menten behavior with substrate inhibition effects at high sucrose concentrations (up to 70% w/v). Additionally, glucose competitive inhibition relating to the sucrose, 1-kestose and nystose uptakes were verified. An inhibitory effect was also noticed with high concentrations of fructose (over 50%) but considered meaningless since the fructose concentration is always low in the actual medium reaction. The hydrolyzing activity over nystose was found to be significant, so it was included in the mathematical model. The initial values for the kinetic constants, Km, Vm and Ki, for each substrate were obtained, and then fine-tuned by simulations, after a parameter sensitivity analysis was carried out. The model predictions fitted well the experimental data, either for the purified or partially purified enzyme, while a different set of adjusted parameters was used in each case. Model predictions for FOS production deviated by not more than 5% in both cases, so they can be used for bioreactor designs.

Dynamics and control strategies for a butanol fermentation process.

In this work, mathematical modeling was employed to assess the dynamic behavior of the flash fermentation process for the production of butanol. This process consists of three interconnected units as follows: fermentor, cell retention system (tangential microfiltration), and vacuum flash vessel (responsible for the continuous recovery of butanol from the broth). Based on the study of the dynamics of the process, suitable feedback control strategies [single input/single output (SISO) and multiple input/multiple output (MIMO)] were elaborated to deal with disturbances related to the process. The regulatory control consisted of keeping sugar and/or butanol concentrations in the fermentor constant in the face of disturbances in the feed substrate concentration. Another objective was the maintenance of the proper operation of the flash tank (maintenance of the thermodynamic equilibrium of the liquid and vapor phases) considering that oscillations in the temperature in the tank are expected. The servo control consisted of changes in concentration set points. The performance of an advanced controller, the dynamic matrix control, and the classical proportional-integral controller was evaluated. Both controllers were able to regulate the operating conditions in order to accommodate the perturbations with the lowest possible alterations in the process outputs. However, the performance of the PI controller was superior because it showed quicker responses without oscillations.

Screening, characterization, and biocatalytic capacity of lipases producing wild yeasts from Brazil biomes

The main goal of this work was to select and characterize lipase producing wild yeasts isolated from different biomes of Brazil. A total of 372 wild yeasts were tested for their lipase producing potential and 3 strains were selected and characterized according to their substrate specificity, pH, and temperature effects and biocatalytic capacity for synthesis in organic media. For the AC02 strain, the optimal enzymatic conditions were pH 7.0 and temperature 44°C, whilst for AAV1 strain, pH 7.0 was also better, but the optimal temperature was 47°C, and for AY3 strain the optimal temperature was 37°C and pH 6.6. About substrate specificity, the lipase from AY3 strain showed higher specificity for short-chain triglycerides. The AC02 strain showed the highest lipolytic activity among the 3 selected, and was molecularly identified by sequencing the ITS1-5.8S-ITS2 and D1/D2 domains of the subunit (26 S) ribosomal DNA as Metschnikowia pulcherrima.