Ordinary Batch Research Articles

Investigation of membrane bioreactor for in situ product removal based on silicone rubber membrane module

In many biotransformation productions performed in ordinary batch or fed-batch bioreactors, product inhibition of a production strain strongly decreases the yield and effectivity of the process. A way to overcome this effect is to apply extractive biotransformation, which means to continually remove the product from the fermentation broth. Nowadays, application of a membrane bioreactor with an immersed capillary membrane module is used as a promising solution for this case. In this work, we propose the membrane bioreactor for extractive bioproduction of chemical specialties consisting of a 3 L mixed tank bioreactor with an immersed extractive tubular membrane module. As the membrane material, silicone rubber tubes were chosen as it shows many advantages compared to other materials. As the model solute for the extraction, 2-phenylethanol (rose aroma) was chosen due to its strong inhibition effect on the production strain (Saccharomyces cerevisiae). The solute partition coefficient in the extraction system containing solute, water and silicone rubber was measured as well as the solute diffusion coefficient for the silicone rubber membrane. Three different membrane modules made of silicone rubber tubes were manufactured and tested in series of extraction experiments performed in the membrane bioreactor at different operation conditions including different biomass concentration, stirring rate, and aeration rate. Experimental data were compared with the prediction of mathematical model programmed in MATLAB with good accuracy.

Microflow Fluorinations of Benzynes: Efficient Synthesis of Fluoroaromatic Compounds.

Fluorinated aromatic compounds are found in a variety of biologically active compounds, including clinical drugs and agrochemicals. Therefore, the synthesis of aryl fluorides is particularly important in the medicinal and process chemistry fields. In this paper, we report a method for the synthesis of aryl fluorides by benzyne fluorination under microflow conditions using the efficient Comet X-01 micromixer. In comparison to our previously reported method under ordinary batch conditions, this approach facilitates a significant reduction in reaction times, to ca. 10 s, as well as increases in the yields of fluoroarenes (by up to 51%).

Potential application of perfusion and pertraction for in situ product removal in biocatalytic 2-phenylethanol production

Abstract Bioproduction of 2-phenylethanol from l -phenylalanine using Saccharomyces cerevisiae is affected by strong product inhibition and thus the maximum reachable concentration in an ordinary batch or fed-batch bioreactor is only about 4 g L −1 . To minimize the effect of product inhibition and to prolong the production period, continual removal of 2-pehnylethanol can be applied. For product removal, adsorption in a fixed bed column can be used but to prevent the column from biomass pollution, a separation method for obtaining a cell free aqueous phase had to be employed before the adsorption step. In this work, the applicability of perfusion and pertraction for obtaining the cell free fermentation medium is studied. Performance of both processes was studied in a series of kinetic measurements with varying concentrations of biomass in a model solution. In case of pertraction, long term stability of supported liquid membrane created by octane was examined. Also, mathematical models of pertraction and perfusion have been verified with experimental measurements. In perfusion experiments, membrane fouling occurred due to the biomass present in feed phase. On the contrary, the biomass did not affect the mass transfer rate during the pertraction. Pertraction was found to be more stable since pores of the membrane are protected from fouling by octane which creates a supported liquid membrane. Octane also forms a barrier for other compounds found in the fermentation medium and can be used for selective transport of 2-phenylethanol to a cell free aqueous solution.

Live to cheat another day: bacterial dormancy facilitates the social exploitation of β-lactamases.

The breakdown of antibiotics by β-lactamases may be cooperative, since resistant cells can detoxify their environment and facilitate the growth of susceptible neighbours. However, previous studies of this phenomenon have used artificial bacterial vectors or engineered bacteria to increase the secretion of β-lactamases from cells. Here, we investigated whether a broad-spectrum β-lactamase gene carried by a naturally occurring plasmid (pCT) is cooperative under a range of conditions. In ordinary batch culture on solid media, there was little or no evidence that resistant bacteria could protect susceptible cells from ampicillin, although resistant colonies could locally detoxify this growth medium. However, when susceptible cells were inoculated at high densities, late-appearing phenotypically susceptible bacteria grew in the vicinity of resistant colonies. We infer that persisters, cells that have survived antibiotics by undergoing a period of dormancy, founded these satellite colonies. The number of persister colonies was positively correlated with the density of resistant colonies and increased as antibiotic concentrations decreased. We argue that detoxification can be cooperative under a limited range of conditions: if the toxins are bacteriostatic rather than bacteridical; or if susceptible cells invade communities after resistant bacteria; or if dormancy allows susceptible cells to avoid bactericides. Resistance and tolerance were previously thought to be independent solutions for surviving antibiotics. Here, we show that these are interacting strategies: the presence of bacteria adopting one solution can have substantial effects on the fitness of their neighbours.

Intensive 2-phenylethanol production in a hybrid system combined of a stirred tank reactor and an immersed extraction membrane module

AbstractBioconversion of l-phenylalanine to 2-phenylethanol using Saccharomyces cerevisiae is connected with the growth of biomass strongly limited by product inhibition. Therefore, fermentation can proceed only at low conversions of l-phenylalanine with very low yield of the desired product, which allows reaching the maximum concentration of 2-phenylethanol, 4 g L−1, in an ordinary batch, fed-batch, or chemostat bioreactor. To minimize capital and operating costs in the bioproduction of chemical specialties where the product inhibits the bioreaction, using a hybrid system based on the application of membrane extraction integrated in the bioreactor to remove the product is a suitable solution. Integration can be done by an external module for membrane extraction or, as a more efficient solution, by an extraction membrane module immersed directly in the bioreactor. Such a hybrid system can be used to remove 2-phenylethanol from the fermentation media and thus to overcome the product inhibition of the biotransformation process. In this paper, a hybrid system consisting of a stirred tank bioreactor (3.5 L) and an immersed extraction hollow fiber membrane module was studied. In the proposed system, the kinetics of 2-phenylethanol extraction from a water solution with and without biomass in the bioreactor to alkanes at different operational conditions was measured. Extraction kinetics was compared with the predictions obtained by a mathematical model. In the hybrid system, two extractive biotransformation experiments were performed and compared with that without product removal. Experimental data were also mathematically predicted with good accuracy between the simulation and the experiment.

Airlift reactor — membrane extraction hybrid system for aroma production

AbstractIn recent times, environmental production methods and organic products are increasingly sought after in food, perfume, and cosmetic industries, where the products are consumed or come into direct contact with humans. One such additive is 2-phenylethanol, an alcoholic aromatic rose like smell compound, mainly used as a flavor and aroma. 2-Phenylethanol can be produced by bioconversion from l-phenylalanine using Saccharomyces cerevisiae. This type of biotransformation is strongly limited by product inhibition which allows reaching the maximum concentration of 2-phenylethanol, 4 g L−1, in an ordinary batch, fed-batch, or chemostat bioreactor. The main aim of the presented work was to study the possible yield increase of 2-phenylethanol in a hybrid system consisting of membrane extraction performed by a hollow fiber membrane module immersed in the downcomer of an airlift reactor. Such hybrid system can be used to remove 2-phenylethanol from the fermentation medium and thus to overcome the product inhibition of biotransformation. In this paper, the influence of biomass on membrane extraction of 2-phenylethanol from aqueous solution in an airlift reactor to alkanes at different operational conditions was studied. The measured extraction kinetics was compared with the predictions obtained by a mathematical model. Hydrodynamics of the hybrid system was also studied.

Production and characterisation of protease enzyme produced by a novel moderate thermophilic bacterium (EP1001) isolated from an alkaline hot spring, Zimbabwe

A moderately thermophilic bacterium designated EP1001 isolated from an alkaline hot spring (conditions in the hot spring: temperature 53-54°C and pH 9.3) in Zimbabwe was investigated for protease production. Studies to determine the growth and protease enzyme production by the novel bacterium were carried out in ordinary batch, regulated batch and fed-batch modes of fermentation using a BioFlow III 3 L fermentor. Biomass production and protease production were dependent on fermentation mode. Higher biomass formation and protease production were obtained in fed-batch fermentations compared with that in ordinary and regulated batch cultivations. The protease enzyme was found to be a thermostable alkaline serine protease with optima activity at 75°C and pH 10. The enzyme had a half life of 45 min at 80°C and 12 h at 70°C. It was stable over the pH range of 5.0 to 11.0. The enzyme was inhibited by phenylmethane-sulfonyl fluoride and EDTA but not by N-Tosyl-L phenanylalanine chloromethyl, iodoacetamide and O-phenathroline. The ions Ca2+ and Fe2+ at 0.5 and 2.5 mM concentration were stimulatory, while Mg2+ and Mn2+ had little effect on the enzyme activity. The enzyme produced by bacterium (EP1001) was concluded to be an alkaline protease that requires calcium and iron ions for its activity. Key words: Protease production, thermophilic bacterium, alkaline hot springs, alkaline protease.

Investigation of 2-phenylethanol production in fed-batch hybrid bioreactor: Membrane extraction and microfiltration

Bioconversion of l-phenylalanine to 2-phenylethanol using Saccharomyces cerevisiae is connected with the growth of biomass which is strongly limited by product inhibition. Therefore, fermentation can proceed only at low conversions of l-phenylalanine with very low yield of the desired product. Maximal concentration of 2-phenylethanol in an ordinary batch, fed-batch or chemostat bioreactor achieves the values of about 4gL−1. The main aim of the present work was to study possible yield increase achieved by continuous separation of 2-phenylethanol such as membrane based solvent extraction (membrane extraction) and cross-flow microfiltration interconnected with a bioreactor in one hybrid system. In this part of the research, membrane extraction of 2-phenylethanol from aqueous phase to alkanes was examined using two different types of hollow fiber membrane modules. The measured extraction kinetics was compared with that obtained by the mathematical model of the membrane extraction at different operational parameters using the partition coefficient of 2-phenylethanol determined by equilibrium experiments. The air-lift reactor was connected with a ceramic multi-channel microfiltration module to study the impact of feed pumping to the microfiltration unit on the air-lift reactor hydrodynamics as well as the influence of different values of biomass concentration, transmembrane pressure, cross-flow velocity and bubbles dragging in the microfiltration unit on the steady-state permeate flux.

Intensification of 2-phenylethanol production in fed-batch hybrid bioreactor: Biotransformations and simulations

2-Phenylethanol is a well-known rose-like aroma widely applied in the cosmetic, perfume and food industries. It can be produced by microbial bioconversion of L-phenylalanine to 2-phenylethanol using Saccharomyces cerevisiae. This biotransformation is connected with the growth of biomass and is strongly limited by product inhibition which allows reaching the maximum concentration of 2-phenylethanol, 4gL−1, in an ordinary batch, fed-batch or chemostat bioreactor. The main aim of the presented work is to study the possible yield increase of 2-phenylethanol using membrane separation techniques such as microfiltration and membrane extraction interconnected with the bioreactor in one hybrid system, which was used to remove 2-phenylethanol from the fermentation medium and thus to overcome the inhibition of biotransformation. In this paper, mathematical model of such a hybrid system is presented. Two fed-batch biotransformations with product removal were carried out at different conditions and they provided higher efficiency of the hybrid system over the classical 2-phenylethanol production. Biotransformation performed in an air-lift reactor was compared with the predictions of the mathematical model with quite good accuracy of the simulated and experimental data. Finally, a sensitivity study of the membrane extraction efficiency in hybrid system under different operation conditions was carried out.

Efficient expression of a Paenibacillus barcinonensis endoglucanase in Saccharomyces cerevisiae

The endoglucanase coded by celA (GenBank Access No. Y12512) from Paenibacillus barcinonensis, an enzyme with good characteristics for application on paper manufacture from agricultural fibers, was expressed in Saccharomyces cerevisiae by using different domains of the cell wall protein Pir4 as translational fusion partners, to achieve either secretion or cell wall retention of the recombinant enzyme. Given the presence of five potential N-glycosylation sites in the amino acid sequence coded by celA, the effect of glycosylation on the enzymatic activity of the recombinant enzyme was investigated by expressing the recombinant fusion proteins in both, standard and glycosylation-deficient strains of S. cerevisiae. Correct targeting of the recombinant fusion proteins was confirmed by Western immunoblot using Pir-specific antibodies, while enzymatic activity on carboxymethyl cellulose was demonstrated on plate assays, zymographic analysis and colorimetric assays. Hyperglycosylation of the enzyme when expressed in the standard strain of S. cerevisiae did not affect activity, and values of 1.2 U/ml were obtained in growth medium supernatants in ordinary batch cultures after 24 h. These values compare quite favorably with those described for other recombinant endoglucanases expressed in S. cerevisiae. This is one of the few reports describing the expression of Bacillus cellulases in S. cerevisiae, since yeast expressed recombinant cellulases have been mostly of fungal origin. It is also the first report of the yeast expression of this particular endoglucanase.

Explicit Solution for Time-Fractional Batch Reactor System

In this paper, the new homotopy perturbation method (NHPM) has been successively applied for finding approximate analytical solutions of the fractional order batch reactor system. An approximate analytical solution for the concentration of reactants and products that is valid for a time interval. The approximate analytical procedure is depends only on two components. The behavior of the solution and effects of different parameters and fractional index are shown graphically. Numerical solutions of ordinary batch reactor system verify our approximate solution with good agreement.

Repeated-batch fermentation using flocculent hybrid, Saccharomyces cerevisiae CHFY0321 for efficient production of bioethanol

In this study, the repeated-batch fermentation of liquefied cassava medium using the flocculent hybrid Saccharomyces cerevisiae CHFY0321 was investigated for semicontinuous, high-throughput production of bioethanol. Cassava medium was selected due to the industrial requirement for a cheap starchy substrate. Fermentations were performed by simultaneous saccharification and fermentation (SSF) with a set of ten batches successfully completing a series within the repeated fermentation process. In addition, pH of the culture medium was not controlled to simplify ethanol production for future use in industry. Optimal recycling volume was found to be 5%. Volumetric productivity, final ethanol concentration, and ethanol yield were measured at 3.34 g l(-1) h(-1), 84.5 g l(-1), and 90.7%, respectively. Cell recycling (24.5 g DCW l(-1)) resulted in 1.8-fold decrease in fermentation time (24 h) and 1.8-fold increase in volumetric productivity compared with the ordinary batch fermentation. Therefore, repeated-batch SSF using flocculent CHFY0321 demonstrates the possibility of cost-effective bioethanol production by eliminating additional saccharification and inoculation steps.

Erlang for Concurrent Programming

Erlang is a language developed to let mere mortals write, test, deploy, and debug fault-tolerant concurrent software. Developed at the Swedish telecom company Ericsson in the late 1980s, it started as a platform for developing soft realtime software for managing phone switches. It has since been open-sourced and ported to several common platforms, finding a natural fit not only in distributed Internet server applications, but also in graphical user interfaces and ordinary batch applications.

Performance analysis of an integrated tangential microfilter‐fermenter

AbstractA specially designed bioreactor including an axial microfilter for cell retention was evaluated for continuous‐flow operation with selected liquid media as controls and in aerobic cultivations of Saccharomyces yeasts. In the initial tests, performance characteristics such as filtration rates and cell accumulation were assessed as a function of filter rotational speed, operating pressure, cultivation time and microfilter type (i.e. membrane or porous metal). The bioreactor did not perform satisfactorily when viscous extracellular polymer was present in the liquid. In the continuous‐flow culture enabling cell retention, Saccharomyces cerevisiae yeast cell concentrations were enhanced by as much as 16‐fold over ordinary batch growth. Concomitant filtration rates were stable over operating times of up to 130 h and hence were independent of the cell concentration. The maximum steady‐state flux was enhanced at rotational speeds up to 400‐700 rpm ranging from 22 to 42 L m−2 h−1. Higher rotation rates offered no further improvements. The maximum stabilized flux was independent of operating pressure. Pressure increases caused momentary flux improvements, which rapidly declined and eventually restabilized. Copyright © 2006 Society of Chemical Industry

Triphase Hydrogenation Reactions Utilizing Palladium‐Immobilized Capillary Column Reactors and a Demonstration of Suitability for Large Scale Synthesis

AbstractWe have developed a practical and highly productive system for hydrogenation reactions utilizing capillary column reactors, which occupy less space than ordinary batch systems, are low cost and easy to handle, and show feasibility toward large‐scale chemical synthesis. Palladium‐containing micelles were immobilized onto the inner surface of the capillaries. Nine palladium‐immobilized capillaries were assembled and connected to a T‐shaped connector, and hydrogen and a substrate solution were fed to capillaries via the connector. Hydrogenation of 1‐phenyl‐1‐cyclohexene (1) proceeded smoothly to give phenylcyclohexane in quantitative yield. The capillaries themselves occupy only ca. 0.4 mL and a high space‐time yield has been achieved (124.3 mg/17 min/0.4 mL). In addition, leaching of palladium was not detected by ICP analysis after reactions.

Kinetic study on glycerol production by repeated batch fermentation using free Candida krusei

The free cells of Candida krusei were recycled during repeated batch fermentation to produce glycerol. The kinetics of glycerol formation with recycled cells washed and not washed was studied. Some inhibition was found during cell recycling but could be removed by washing recycled cells. In 12 cycles of repeated batch fermentation with recycled washed cells, glycerol productivity increased greatly during the earlier three cycles and then remained constant in the following cycles. Kinetic studies showed that higher glycerol productivity in repeated batch fermentation compared with that in ordinary batch fermentation was due to the high biomass concentration.

Energy Conservation by Multi-Effect Batch Distillation System.

A multi-effect batch distillation system, MEBAD, which separates multiple components simultaneously, has higher energy effeciency compared with an ordinary batch distillation column. In this paper, in order to make the characteristics of the MEBAD clearer, the energy consumption of the MEBAD is compared with that of a conventional continuous distillation system for various feed conditions. Results of the exhaustive simulations show that the MEBAD has the potential for having a higher energy efficiency than a continuous system when the number of components is increased or relative volatilities among the components are decreased. Furthermore, it is shown that there is little relationship between the number of column stages and the energy consumption at the reboiler of the MEBAD while the number of stages strongly affects the energy consumption of the continuous system. The reason why the number of stages does not affect the energy consumption of the MEBAD is explained from the relationship between the operating line and the VLE curve.

A generic framework for an on-line scheduling and control system in batch process management

On-line scheduling and control systems, which dynamically adjust production schedules according to changes in scheduling conditions, are a vital issue in modern batch processes because of their dynamic behavior and the unpredictable market situation. In this paper, we propose a generic on-line scheduling and control framework to handle a wide variety of uncertainties by utilizing proven external scheduling algorithms. The framework provides fundamental mechanisms to define schedule modification timing and a modification space according to the changes of scheduling conditions, and dynamically modifies a schedule to minimize the effect of the changes by using adequate scheduling algorithms for each situation. The basic structure and mechanisms of the framework are described. Performance of the framework against typical fluctuations in ordinary batch process operations is demonstrated via simulation experiments with a multiproduct batch plant.

Simultaneous Separation of Light and Heavy Impurities by a Complex Batch Distillation Column.

The characteristics of a new type of batch distillation column called the “complex batch distillation column” are examined. In the complex column, the feed is supplied to the middle of the column, and the light and heavy components are withdrawn from the top and the bottom at the same time. The liquid on the feed tray is recycled to the feed tank so as to accumulate the intermediate component in the tank. The complex column is convenient for removing light and heavy impurities from raw materials since the impurities can be withdrawn simultaneously from the top and the bottom. The complex column is similar to a combined system of ordinary and stripping batch distillation columns where the condenser of the stripping column is heat-integrated with the reboiler of the ordinary column. Therefore, it can be expected that separation can be executed effectively compared with the ordinary column. In this paper, by analyzing the differences between ordinary and stripping batch distillation columns, the conditions at which the complex column works effectively compared with an ordinary batch distillation column, are clarified.

Comparison of the Separation Performances of a Multi-Effect Batch Distillation System and a Continuous Distillation System

A new type of batch distillation system which separates multiple components simultaneously is proposed. The features of this system are that the steam is supplied to the reboiler of the first column only, and a condenser of one column is heat-integrated with the reboiler of the next column. Therefore, the energy required to separate multiple components is markedly less than that of an ordinary batch distillation system. The energy consumption of the proposed system is compared with that of an ordinary continuous distillation system. Through simulation, it is found that the proposed system has the potential to have a better separation performance than a continuous system if the number of products is increased.