Isopropanol-butanol-ethanol production by cell-immobilized vacuum fermentation.

The Isopropanol-Butanol-Ethanol productivity by solventogenic clostridia can increase when cells are immobilized on low-cost, renewable fibrous materials; however, butanol inhibition imposes the need for dilute sugar solutions (less than40 g/L). To alleviate this problem, the in-situ vacuum product recovery technique was applied to recover IBE in repeated-batch cultivation of Clostridium beijerinckii DSM 6423 immobilized on sugarcane bagasse. Five repeated batch cycles were conducted in a 7-L bioreactor containing P2 medium (∼60 g/L glucose) and bagasse packed in 3D-printed concentric annular baskets. In three cycles, glucose was consumed by 86% on average, the IBE productivity was 0.35 g/L∙h or 30% and 17% higher relative to free- and immobilized (without vacuum)-cell cultures. Notably, the product stream contained 45 g/L IBE. However, the fermentation was unsatisfactory in two cycles. Finally, by inserting a fibrous bed with hollow annuli in a vacuum fermentation, this work introduces the concept of an internal-loop boiling-driven fibrous-bed bioreactor.

Sugarcane bagasse hydrolysates as feedstock to produce the isopropanol-butanol-ethanol fuel mixture: Effect of lactic acid derived from microbial contamination on Clostridium beijerinckii DSM 6423.

Enzymatic hydrolysis of lignocellulose under industrial conditions is prone to contamination by lactic acid bacteria, and in this study, a cellulose hydrolysate produced from dilute-acid pretreatedsugarcane bagasse contained 13 g/L lactic acid and was used for IBE production by Clostridium beijerinckii DSM 6423. In fermentation of the cellulose hydrolysate supplemented with sugarcane molasses for nutrients and buffering of the medium (40 g/L total sugar), 92% of the lactic acid was consumed, and the butanol yield was as high as 0.28 (7.9 g/L butanol), suggesting that lactic acid was preferentially metabolized to butanol. When the hydrolysate was mixed with a detoxified bagasse hemicellulose hydrolysate and supplemented with molasses (35 g/L total sugar), the culture was able to exhaust glucose and utilized sucrose (by 38%), xylose (31%), and lactic acid (70%). Overall, this study shows that C. beijerinckii DSM 6423 can co-ferment first- and second-generation sugars while consuming lactic acid.

Acetone-free biobutanol production: Past and recent advances in the Isopropanol-Butanol-Ethanol (IBE) fermentation.

Production of butanol for fuel via the conventional Acetone-Butanol-Ethanol fermentation has been considered economically risky because of a potential oversupply of acetone. Alternatively, acetone is converted into isopropanol by specific solventogenic Clostridium species in the Isopropanol-Butanol-Ethanol (IBE) fermentation. This route, although less efficient, has been gaining attention because IBE mixtures are a potential fuel. The present work is dedicated to reviewing past and recent advances in microorganisms, feedstock, and fermentation equipment for IBE production. In our analysis we demonstrate the importance of novel engineered IBE-producing Clostridium strains and cell retention systems to decrease the staggering number of fermentation tanks required by IBE plants equipped with conventional technology. We also summarize the recent progress on recovery techniques integrated with fermentation, especially gas stripping. In addition, we assessed ongoing pilot-plant efforts that have been enabling IBE production from woody feedstock.

Separation and purification of fructooligosaccharides on a zeolite fixed-bed column.

Fructooligosaccharides (FOS), a well-known prebiotic product, are obtained by enzymatic synthesis and consist of a mixture of mono- and disaccharides. In this work, a methodology for their separation and purification was developed using a zeolite fixed-bed column. The effects of column temperature (40-60°C), eluent flow rate (0.10-0.14 mL/min), injected to bed volume percent ratio (2.6-5.1%), and ethanol concentration in the eluent (40-60%, v/v) were investigated using a fractionary factorial design (2(4-1)), having the separation efficiency and purity as target responses. Additional experiments were performed as well, where the temperature and ethanol concentration were studied in a central composite design (2(2)). In this work, the zeolite fixed-bed column was shown to be a good alternative for FOS purification, allowing a FOS purity of 90% and separation efficiency of 6.86 between FOS and glucose, using an eluent at 45°C with 60% ethanol concentration.

Kinetic modeling of ethanol production by Scheffersomyces stipitis from xylose.

This work focuses on the kinetics of ethanol production by Scheffersomyces stipitis on xylose with the development of a mathematical model considering the effect of substrate and product concentrations on growth rate. Experiments were carried out in batch and continuous modes, with substrate concentration varying from 7.2 to 145 g L(-1). Inhibitory effects on cell growth, substrate uptake, and ethanol production rates were found to be considerable. Kinetic parameters were obtained through linear and non-linear regression methods. Experiments in continuous mode were performed at different dilution rates to evaluate the inhibitory effect of ethanol. A mixed mathematical model which combined Andrews and Levenspiel's models, combining substrate and product inhibition, was used. A quasi-Newton routine was applied to obtain a more accurate fitting of kinetic parameters. The parameters such as cell to product factor (YP/X) and limiting cell yield (YX) were shown to be dependent on substrate concentration. The kinetic model fitted satisfactorily the experimental data.

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.

Cellulase production from a new strain Acremonium strictum isolated from the Brazilian Biome using different substrates.

The objective of the present study was to evaluate the production of cellulolytic enzymes by Acremonium strictum isolated from Brazilian Biome using different substrates. Fermentations were initially carried out using commercial substrates, including microcrystalline cellulose (AVICEL® and SERVACEL®) and carboxymethylcellulose (CMC). This was followed by fermentations performed using lignocellulosic biomass: sugarcane bagasse pretreated at different intensities. The fermentations were carried out in shakers at 150 rpm, 30 °C for 240 h. Four enzyme activities were determined: CMCase, FPase, cellobiase and ß-glucosidase. Among the substrates used, results showed that the sugarcane bagasse submitted to mild pretreatment was that which induced the microorganism to produce greater cellulolytic activities. This substrate was employed in the optimization study of cellulase production by A. strictum.

Separation of fructooligosaccharides using zeolite fixed bed columns.

Recent studies have shown that the chromatographic separation of mixtures of monosaccharides and disaccharides may be improved by employing Y zeolites, a procedure which holds promise in the separation of oligosaccharides. In the present study, a column packed with zeolite was employed to study the separation of fructooligosaccharides (FOS). FOS were produced by an enzyme isolated from Rhodotorula sp., which produces GF2 (kestose), GF3 (nystose) and GF4 (frutofuranosyl nystose). The identification and quantification of the sugars were carried out by ion exchange chromatography with pulsed amperometric detection (HPAEC-PAD). The separation of fructooligosaccharides was carried out using a fixed bed column packed with Ba2+-exchange Y zeolites. The effects of temperature (40-50 degrees C), injected volume per bed volume (2.55-7.64%), superficial velocity (0.1-0.15 cm min(-1)) and eluent composition (40-60% ethanol) were investigated using a fractionary factorial design with separation efficiency as the response. The results showed that the most favorable conditions for the separation of the oligosaccharide-glucose mixture were 60% ethanol as eluent, temperature of 50 degrees C, superficial velocity of 0.1 cm min(-1) and 2.55% injection volume per bed volume of injection mixture, using two columns in series. The values for separation efficiency were 0.60 for oligosaccharide-glucose, 1.00 for oligosaccharide-fructose, 0.22 for oligosaccharide-sucrose, 0.43 for glucose-fructose, 0.82 for glucose-sucrose and 1.23 for fructose-sucrose.

Production of lactic acid from sucrose: strain selection, fermentation, and kinetic modeling.

Lactic acid is an important product arising from the anaerobic fermentation of sugars. It is used in the pharmaceutical, cosmetic, chemical, and food industries as well as for biodegradable polymer and green solvent production. In this work, several bacterial strains were isolated from industrial ethanol fermentation, and the most efficient strain for lactic acid production was selected. The fermentation was conducted in a batch system under anaerobic conditions for 50 h at a temperature of 34 degrees C, a pH value of 5.0, and an initial sucrose concentration of 12 g/L using diluted sugarcane molasses. Throughout the process, pulses of molasses were added in order to avoid the cell growth inhibition due to high sugar concentration as well as increased lactic acid concentrations. At the end of the fermentation, about 90% of sucrose was consumed to produce lactic acid and cells. A kinetic model has been developed to simulate the batch lactic acid fermentation results. The data obtained from the fermentation were used for determining the kinetic parameters of the model. The developed model for lactic acid production, growth cell, and sugar consumption simulates the experimental data well.

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.

Technical viability of the production, partial purification and characterisation of inulinase using pretreated agroindustrial residues.

The present work aimed to study the viability of the use of sugarcane molasses and corn steep liquor (CSL) in a sequential inulinase production performing an up-stream pretreatment of these agroindustrial residues. A sequential strategy was used applying three central composite rotatable designs (CCRDs) to optimise medium composition, followed by a down-stream step. The medium containing 150 g L(-1) molasses, 50 g L(-1) CSL and 6 g L(-1) yeast extract, yielded a maximum inulinase production of 1,294 +/- 7 U mL(-1), after 72 h of fermentation. A down-stream evaluation was carried out using an expanded bed of Streamline DAE resin (Pharmacia), with and without the up-stream treatment. The results showed that the enzyme could not be recovered from the non-pretreated medium, whereas a yield of 91% was obtained in the adsorption stage from the medium prepared with the up-stream treatment, showing the viability of producing the enzyme inulinase from agroindustrial residues using the integrated 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.

Estimation of temperature dependent parameters of a batch alcoholic fermentation process.

In this work, a procedure was established to develop a mathematical model considering the effect of temperature on reaction kinetics. Experiments were performed in batch mode in temperatures from 30 to 38 degrees C. The microorganism used was Saccharomyces cerevisiae and the culture media, sugarcane molasses. The objective is to assess the difficulty in updating the kinetic parameters when there are changes in fermentation conditions. We conclude that, although the re-estimation is a time-consuming task, it is possible to accurately describe the process when there are changes in raw material composition if a re-estimation of parameters is performed.

Otimizaçäo da produçäo de dextrana-sacarase de leuconostoc mesenteroides à partir de melaçäo como fonte de carbono / Otimization of the production of dextransurase from leuconostoc mesenteroides using molasses as carbon source

Resumo: A produçäo de dextrana-sacarase de Leuconostoc mesenteroides B-512F foi realizada em meios de fermentaçäo de milho, como fontes de carbono e nutrientes. Os resultados obtidos näo foram muito diferentes daqueles obtidos com um meio bem mais rico. O melhor procedimento em fermentaçäo foi a batelada alimentada com controle do pH. A produtividade foi 13 (po cento superior ao resultado obtido com meio rico (au)

SCP production from organic acids with Candida utilis

O crescimento de Candida utilis foi estudado em culturas em batelada e em culturas contínuas tendo como fonte de carvbono ácido acético, ácido propiônico e ácido butírico. Estes compostos mostraram ser tóxicos e altamente inibidores em concentraçöes relativamente baixas. O rendimento de biomassa diminue à medida em que a concentraçäo do substrato aumento. Estudou-se igualmente a manutençäo celular em ácidos orgânicos. O microrganismo pode utilizar de 5 a 44,8% de substrato para para manutençäo. Candida utilis desenvolveu-se bem em efluentes ácidos provenientes de fermentaçäo acidogênica. Mostrou-se que o uso destes efluentes para produçäo de SCP (proteína de organismo unicelulares) é possível e interessante