Showing papers in "Bioprocess Engineering in 1989"
TL;DR: A shearbased mechanism and the ratio of smallest eddy size to microcarrier diameter can explain the beneficial effects of both smaller diameter microcarriers and higher viscosity of the medium on the growth rate of bovine embryonic kidney cells.
Abstract: Bead-bead collisions have been characterized using the velocity of the smallest turbulent eddies to calculate a turbulent collision severity (defined as the energy of collisions times their frequency), but a shear-based collision mechanism with a different dependence on the system variables is also applicable. This shearbased mechanism and the ratio of smallest eddy size to microcarrier diameter can explain the beneficial effects of both smaller diameter microcarriers and higher viscosity of the medium on the growth rate of bovine embryonic kidney cells. Death rates of these cells have also been measured at several levels of agitation. The decrease in apparent growth rate from increasing agitation is caused both by a higher rate of cell death as well as a lower intrinsic growth rate.
59 citations
TL;DR: In this article, the effectiveness of separation in different systems of dynamic filtration, both mechanical and crossflow, has been compared and the energy demand for these processes has also been compared.
Abstract: In this paper the effectiveness of separation in different systems of dynamic filtration, both mechanical and crossflow filtration, has been compared. Apart from the filtration rate obtained under comparable conditions the energy demand for these processes has also been compared. The obtained results show that dynamic mechanical filtration can in some cases be more effective than the more commonly used crossflow filtration.
46 citations
TL;DR: The effect of biomass recycle at a variety of dilution rates and recycle ratios under both glucose and non-glucose limited conditions on product yields and selectivities has been investigated.
Abstract: The availability and demand of biosynthetic energy (ATP) is an important factor in the regulation of solvent production in steady state continuous cultures of Clostridium acetobutylicum. The effect of biomass recycle at a variety of dilution rates and recycle ratios under both glucose and non-glucose limited conditions on product yields and selectivities has been investigated. Under conditions of non-glucose limitation, when the ATP supply is not growth-limiting, a lower growth rate imposed by biomass recycle leads to a reduced demand for ATP and substantially higher acetone and butanol yields. When the culture is glucose limited, however, biomass recycle results in lower solvent yields and higher acid yields.
45 citations
TL;DR: The hybridoma cell's maximum capacity for monoclonal antibody (MAb) production is estimated to be 2300–8000 MAb molecules/cell/s, using measured rates of transcription and translation, and the limitations imposed by the size of the polymerase molecule and the ribosome.
Abstract: The hybridoma cell's maximum capacity for monoclonal antibody (MAb) production is estimated to be 2300–8000 MAb molecules/cell/s, using measured rates of transcription and translation, and the limitations imposed by the size of the polymerase molecule and the ribosome. Nearly all the production rates reported in the literature fall into or below this range of production rates. Data from batch cultures of hybridomas demonstrate a constant specific rate of MAb production until the time integral of the viable cell concentration reaches about 108 cells · h/cm3. At this point, some essential nutrients from the standard media are depleted, causing MAb production to decline.
45 citations
TL;DR: Using experimental data from continuous cultures of Clostridium acetobutylicum with and without biomass recycle, relationships between product formation, growth and energetic parameters were explored, developed and tested.
Abstract: The availability and demand of biosynthetic energy (ATP) is an important factor in the regulation of solvent production in steady state continuous cultures of Clostridium acetobutylicum. The effect of biomass recycle at a variety of dilution rates and recycle ratios under both glucose and non-glucose limited conditions on product yields and selectivities has been investigated. Under conditions of non-glucose limitation, when the ATP supply is not growth-limiting, a lower growth rate imposed by biomass recycle leads to a reduced demand for ATP and substantially higher acetone and butanol yields. When the culture is glucose limited, however, biomass recycle results in lower solvent yields and higher acid yields.
41 citations
TL;DR: It is postulated that to achieve steady-state solvent production over extended periods of time, it is necessary to maintain a balance among the various morphological cell forms, i.e. acid-producing vegetative cells, solvent-producing clostridial cells, and inert forms, e.g. spores.
Abstract: A continuous bioreactor where cells were recycled using a cross-flow microfiltration (CFM) membrane plant was investigated for the production of solvents (ABE fermentation) from whey permeate using Clostridium acetobutylicum P262. A tubular CFM membrane plant capable of being backflushed was used. The continuous fermentations were characterized by cyclic solventogenic and acidogenic behaviour, and ultimately degenerated to an acidogenic state. Steady-state solvent production was obtained for only short periods. This degeneration is attributed to the complex morphological behaviour of this strain of organism on this substrate. It is postulated that to achieve steady-state solvent production over extended periods of time, it is necessary to maintain a balance among the various morphological cell forms, i.e. acid-producing vegetative cells, solvent-producing clostridial cells, and inert forms, e.g. spores.
39 citations
TL;DR: In this article, two strains of X. campestris from a collection and a wild strain isolated from infected cabbage were cultured in a defined medium in a 25 dm3 fermenter.
Abstract: Two strains of X. campestris from a collection and a wild strain isolated from infected cabbage were cultured in a defined medium in a 25 dm3 fermenter. The rheological characteristics of the broth were measured using a Weissenberg rheogoniometer. The rheological behaviour over a wide range of shear rates could be described with the power law model and a yield stress was obtained using the Herschel-Bulkley equation. As expected, the broth's flow behaviour is highly influenced by gum concentration. In general, the rheological parameters during the fermentations varied within the following ranges: K (2–210 dyn-sn/cm2), n (0.2–0.9), τ
y
(0.02–50 dyn/ cm2), with strain 1459 reaching the maximum values as well as the highest gum concentration. Differences in flow behaviour could be associated with different molecular configurations of the polymers produced by the different strains. Heat treatment of the broths change the rheological characteristics, increasing K and decreasing n. Reconstituted solutions of all sterilized gums exhibited similar rheological characteristics and, at low concentrations, also similar to those of a commercial xanthan.
37 citations
TL;DR: The optimum design of a series of mixed reactors containing immobilized biocatalysts is described, and a detailed description is given of the modelling of internal diffusion and reaction in the beads, and external mass transfer resistance.
Abstract: The optimum design of a series of mixed reactors containing immobilized biocatalysts is described. A detailed description is given of the modelling of internal diffusion and reaction in the beads, and external mass transfer resistance. The model is validated by experiments with cascades of two and three reactors, containing immobilized invertase. For that, invertase was first bound to DE32-cellulose anion exchanger and then entrapped in Calcium Alginate.
30 citations
TL;DR: In this article, the most significant process engineering aspects involved in the bacterial leaching of copper ores are discussed, i.e. bacterial population, type of mineral and particle size, nutrients and inhibitors, oxygen and carbon dioxide, temperature and pH, leaching kinetics and operation mode.
Abstract: The bioleaching of minerals is a complex process that is affected by a number of biological, mineralogical, electrochemical and engineering factors. This work presents and discusses the most significant process engineering aspects involved in the bacterial leaching of copper ores, i.e. bacterial population, type of mineral and particle size, nutrients and inhibitors, oxygen and carbon dioxide, temperature and pH, leaching kinetics and operation mode.
29 citations
TL;DR: Results on the solubilization of ribonuclease-a and concanavalin-a in Aerosol-OT/isooctane organic solvents were well-correlated by the model equation, and the estimated parameters were of the expected order of magnitude as estimated based on the known physical properties of the system components.
Abstract: A simple thermodynamic model is developed for the partitioning of proteins between a bulk aqueous solution and a reversed micellar organic phase by assuming that a pseudo-chemical equilibrium is established when proteins in solution interact with a non-integral number of empty micelles to form the protein-micelle complex. From the equilibrium constant for this reaction, which is related to both the chemical and electrical free energy changes associated with the transfer of the proteins between the two phases, a simple expression is derived for the partition coefficient as a function of pH and surfactant concentration. Assumptions include a linear variation in protein net charge with pH, and a linear decrease in protein-micelle complex size with increasing protein charge. Results on the solubilization of ribonuclease-a and concanavalin-a in Aerosol-OT/isooctane organic solvents were well-correlated by the model equation, and the estimated parameters were of the expected order of magnitude as estimated based on the known physical properties of the system components.
27 citations
TL;DR: In this article, a three phase fluidized sand bed reactor design was improved by adding a draft tube to improve fluidization and submerged effluent tubes for sand separation, which greatly reduced the aeration rate required for sand suspension.
Abstract: A previous three phase fluidized sand bed reactor design was improved by adding a draft tube to improve fluidization and submerged effluent tubes for sand separation. The changes had little influence on the oxygen transfer coefficients(K
L a), but greatly reduced the aeration rate required for sand suspension. The resulting 12.5 dm3 reactor was operated with 1 h liquid residence time, 10.2dm3/min aeration rate, and 1.7–2.3 kg sand (0.25–0.35 mm diameter) for the degradation of phenol as sole carbon source. The K
La of 0.015 s−1 gave more than adequate oxygen transfer to support rates of 180g phenol/h · m3 and 216 g oxygen/h · m3. The biomass-sand ratios of 20–35 mg volatiles/g gave estimated biomass concentrations of 3–6 g volatiles/dm3. Offline kinetic measurements showed weak inhibition kinetics with constants ofK
s=0.2 mg phenol/dm3, K
o2=0.5 mg oxygen/dm3 and KinI= 122.5 mg phenol/dm3. Very small biofilm diffusion effects were observed. Dynamic experiments demonstrated rapid response of dissolved oxygen to phenol changes below the inhibition level. Experimentally simulated continuous stagewise operation required three stages, each with 1 h residence time, for complete degradation of 300 mg phenol/dm3 · h.
TL;DR: A porous glass sponge with free permeable macropores that can be colonized by anaerobic microorganisms proved to be especially useful, and Raschig ring-shaped particles of this material were used in fixed-bed loop reactors for the anaerobia digestion of organically high polluted effluents.
Abstract: A chemostat is well known to be a tool for selecting microorganisms with minimum doubling times during continuous fermentation, which is of special importance for slowly growing microorganisms like those used in anaerobic digestion. By set point control (SPC) of the operation parameters — especially of residence time τ — by means of a process computer, the selection stress can be optimized. A continuous operation very close to wash-out conditions is possible in spite of the microorganisms population changing properties. For anaerobic digestion of acid, a biomass was obtained that could reduce the chemical oxygen demand (COD) by more than 20 kg per kg dry biomass per d. For a high space-time yield, not only a high biomass activity but also a high biomass concentration is needed; therefore, methods for biomass retention or recycling have been developed. A porous glass sponge with free permeable macropores that can be colonized by anaerobic microorganisms proved to be especially useful. Raschig ring-shaped particles of this material were used in fixed-bed loop reactors for the anaerobic digestion of organically high polluted effluents.
TL;DR: In this article, E. Coli (E. C. 3.5.1.11) was covalently bound via glutaric aldehyde to acrylic carriers cross-linked with divinylbenzene or ethylene glycol dimethacrylate.
Abstract: Penicillin acylase obtained from E. Coli (E. C. 3.5.1.11) was covalently bound via glutaric aldehyde to acrylic carriers cross- linked with divinylbenzene or ethylene glycol dimethacrylate. The best enzymatic preparation was obtained by using ethyl acrylate/ ethylene glycol dimethacrylate copolymer. I cm 3 of the carrier bound 6.4 mg of protein, having 72% activity in relation to the native enzyme. The preparation lost only 10% of its initial activity after 100 d of storage at 4~ A negligible effect of immobilization on the enzyme activity at different temperatures or pH as well as significant increase of the stability of the immobilized enzyme at elevated temperatures were observed.
TL;DR: The possibility of Pseudomonas fluorescens lipase purification by using ultrafiltration capillar membranes was studied and two step procedure for protein fractionation on polyacrylonitryle and enzyme concentration on polysulphone membranes was proposed.
Abstract: The possibility of Pseudomonas fluorescens lipase purification by using ultrafiltration capillar membranes was studied. Two step procedure for protein fractionation on polyacrylonitryle, and enzyme concentration on polysulphone, membranes was proposed. This procedure is suitable for continuous lipase recovery.
TL;DR: In this paper, two fixed-bed loop reactors were used to evaluate single and separated-phase anaerobic treatments of a high strength waste-water from ethanol fermentation, and they were operated under steady state and variable process conditions.
Abstract: Two fixed-bed loop reactors were used to evaluate singleand separated-phase anaerobic treatments of a high strength waste-water from ethanol fermentation. The one-phase system consisted of an anaerobic fixed-bed loop reactor containing both acidogenic as well as methanogenic populations allowing a complete conversion of the carbon source into gaseous end products and biomass. The two-phase system consisted of a second fixed-bed loop reactor operated as a methanogenic unit, which was proceeded by a CSTR for acidification, both connected in series allowing sequential acidogenesis and methanogenesis of the organic components. The reactors were operated under steady state and variable process conditions. By gradually increasing the feed supply in both systems, maximum turnover of COD was determined. The separated-phase system consistently gave a better quality effluent with lower suspended solids and total COD. Maximum loading rates and COD elimination of the methanogenic phase of the two-phase system was over two times higher than that of the one-phase system. Process stability was also higher. On overloading the methane reactor of the two phase system accumulation of different fatty acids within the reactor was observed. Hydrogen concentration in the biogas can be used as a reliable indicator for system overloadings. At least, continuous online monitoring of hydrogen in the methanogenic reactor gas should provide a convenient alternative to other analyses for process control.
TL;DR: Fractionation of the yeast-produced proteins during this carry-over process is described, based on gel electrophoresis analyses of both the carried-over proteins and the extracellular proteins in the fermentation bed.
Abstract: Baker's yeast was grown on a semi-solid substrate (homogenized whole potatoes) in an air-fluidized bed fermentor, in which a rapid stream of air simultaneously supplied oxygen and mixed the semi-solid substrate. The potato starch was converted to reducing sugars by α-amylase (from Aspergillus). During the course of the batch fermentation, some secreted yeast proteins were trapped by sparging the effluent air into a water chamber. Surprisingly, neither the α-amylase nor the potato proteins were the most predominant proteins carried over to the overhead collector during the 24 h run, even though they were the most abundant proteins in the fermentation mash. Fractionation of the yeast-produced proteins during this carry-over process is described, based on gel electrophoresis analyses of both the carried-over proteins and the extracellular proteins in the fermentation bed. Effects of the operating variables on the extracellular protein levels in the fermentation bed and the proteins in the overhead collector are also discussed.
TL;DR: In this article, the improved effluent control of industrial anaerobic digestion treatment systems is described, and a modification to the existing algorithm, based on a new control technique known as Generic Model Control, that simplifies and improves the robustness of the control algorithm is presented.
Abstract: This paper describes the improved effluent control of industrial anaerobic digestion treatment systems. Previous research has shown the possibility of applying a model-based adaptive control technique to these processes. This paper reviews this technique and shows that improved controllability can be obtained by a modification to the existing algorithm, based on a new control technique known as Generic Model Control, that simplifies and improves the robustness of the control algorithm.
TL;DR: Development of procedures for describing the performance of devices where enzyme-catalyzed reactions between two substrates take place are concentrated on, and for the rational design and optimization of the reactors considered.
Abstract: Utilization of enzymic reactors for biotechnological-biomedical applications is currently developing at a sustained pace.
TL;DR: In this paper, the authors used the diaphragm cell method to determine the diffusion coefficient of sucrose, a carbon source for xanthan production, using similar concentrations to those occurring in a typical fermentation.
Abstract: Molecular diffusion of solutes, like sucrose in the xanthan gum fermentation, is important in order to understand the complex behavior of mass transfer mechanisms during the process. This work was focused to determine the diffusion coefficient of sucrose, a carbon source for xanthan production, using similar sucrose and xanthan concentrations to those occurring in a typical fermentation. The diaphragm cell method was used in experimental determinations. The data showed that diffusion coefficient of sucrose significantly decreases when xanthan gum concentration increases. Theoretical and semiempirical models were used to predict sucrose diffusivity in xanthan solutions. Molecular properties and rheological behavior of the system were considered in the modeling. The models tested fitted well the behavior of experimental data and that reported for oxygen in the same system.
TL;DR: Tangential flow filtration of a biotransformation medium of 6-α-methylhydrocortisone to 6- α-methylprednisolone (medrol) was carried out to study the recovery of the product, from heattreated cell suspensions of Arthrobacter simplex, with higher product recovery rate when concentration of the medium was performed prior to the diafiltration.
Abstract: Tangential flow filtration of a biotransformation medium of 6-α-methylhydrocortisone to 6-α-methylprednisolone (medrol) was carried out to study the recovery of the product, from heattreated cell suspensions of Arthrobacter simplex. A higher product recovery rate was achieved when concentration of the medium was performed prior to the diafiltration. The concentration of the product in the permeate was also higher when concentration is the first mode of operation. Combined anionic and cationic microsized polymeric particles were used as filtration aids. These resins flocculated cells of A. simplex and allowed a 5-fold enhancement in the recovery rate of the product, through a 0.22 μm Durapore membrane, by increasing the diafiltration flux from 20 dm3/hm2 to 125 dm3/hm2. The medrol rejection coefficient remained constant when the polymeric particles were used, being highly dependent on the cell concentration.
TL;DR: In this paper, a theoretical analysis of the process at a large scale is presented, and the results of this analysis are compared with results from fed-batch experiments, and it is concluded that if only one mechanism is ruling the process, for instance mass transfer, the results are quite clear.
Abstract: The scale-down procedure can be used to optimize and scale up fermentation processes. The first step in this procedure, a theoretical analysis of the process at a large scale, must give information about the regime, or bottle necks, ruling the process. In order to verify the theoretical results the process analysis has been applied to the fed-batch baker's yeast production at a laboratory scale. The results of this analysis are compared with results from fed-batch experiments. It was concluded that if only one mechanism is ruling the process, for instance mass transfer, the results of the analysis are quite clear. If more than one mechanism is important, for example mass transfer and liquid mixing, additional knowledge is needed to predict the behaviour of the process.Concerning the baker's yeast production, it was concluded that if oxygen limitation occurs, liquid mixing is of little importance.
TL;DR: A model for microbial growth based on the assumption that the rate of biomaterial synthesis relates to rates of catabolism end-products evolution is applied for description of baker's yeast growth under carbon and oxygen limitation.
Abstract: A model for microbial growth based on the assumption that the rate of biomaterial synthesis relates to rates of catabolism end-products evolution is applied for description of baker's yeast growth under carbon and oxygen limitation. A method for estimating the parameters of the model is demonstrated. Kinetic expressions both for the saturated respiratory capacity and the repression of respiration are discussed.
TL;DR: A structured model of Zymomonas mobilis is presented using fermentation data of a defined aspartate medium and the results are shown as simulations and the inhibitory effect of ethanol on the bacterial cell is discussed.
Abstract: A structured model of Zymomonas mobilis is presented using fermentation data of a defined aspartate medium. After some remarks on the structure of the metabolism the model is derived by considering sub-models, e.g. balance equations, and by identifying the unknown parameters separately for each sub-model. Some results are the elemental composition of Zymomonas mobilis, a description of the substrate uptake during substrate limitation and the growth inhibition during substrate saturation. The results are shown as simulations and are discussed in relation to the inhibitory effect of ethanol on the bacterial cell.
TL;DR: This study was part of a comprehensive effort to elucidate the behavior of recombinant yeast and establish the effects of yeast nitrogen base without amino acids medium and leucine selection.
Abstract: Saccharomyces cerevisiae cultures were selected to determine the effects of plasmid size on host growth kinetics and plasmid copy number. A complete synthetic medium was verified and the effects of yeast nitrogen base without amino acids medium and leucine selection were established for the strain. The dependence of copy number on the plasmid size, medium, and oxygen availability was also measured. This study was part of a comprehensive effort to elucidate the behavior of recombinant yeast.
TL;DR: In this article, a mathematical model for the chromatographic separation of xylose and mannose on an ion exchange resin in the Pb form was proposed, where dispersion in the mobile phase, external mass transfer around the particles and internal diffusion were taken into account.
Abstract: A mathematical model was proposed for the chromatographic separation of xylose and mannose on an ion-exchange resin in the Pb form: dispersion in the mobile phase, external mass transfer around the particles and internal diffusion were taken into account. Small-scale experiments provided an evaluation of the different parameters. Dispersion in the mobile phase was found to be the predominant phenomenon. The Peclet numbers were calculated by identification in the Laplace domain of the elution profiles. Influence of temperature and initial concentration of the sample were studied.
TL;DR: In this paper, the rate coefficients for the liquid phase mass transfer controlled cation exchange process were calculated and interrelated with a plot of jMfactor versus Reynolds number, and the effect of scale up on ion exchange process was investigated.
Abstract: Kinetics of the separation of L-glutamic acid (GLU) by ion exchange has been studied with strongly acidic H+-type cation exchange resin Amberlite IR-122. Since glutamic acid is a trivalent ampholyte and dissociates according to three equilibrium reactions, separation of G+ ions by a cation exchange process is accompanied by the dominant reversible reaction, i.e. G++H+ ⇄ G0. Accompanying reversible reaction has an effect on the ion exchange rate, and decreases the performance of the process comparing with the ideal case that the exchanging ions retain their identity. The analysis was performed first with the ion exchange column, DIC (L/D=0.52); and then with the ion exchange column, IC (L/D=10.9). The data were collected with model glutamic acid solutions for both DIC and IC columns/reactors. IC experimental results were then compared with that of DIC and the effect of scale up on ion exchange process was investigated. The experimental results have provided an adequate basis for the design calculations, and the design parameters were determined. Rate coefficients for the liquid phase mass transfer controlled cation exchange process were calculated and interrelated with a plot of jMfactor versus Reynolds number.
TL;DR: The scale-up of hydrophobic interaction chromatography for purification of SN-07 resulted in decreasing the required amount of salt, and the adsorption capacity increased with an increase in the ligand concentration.
Abstract: Scale-up of hydrophobic interaction chromatography for purification of SN-07 was studied. The height equivalent to a theoretical plate of the adsorbent gel (Sepabeads FP-PH 12) was kept constant for various superficial liquid velocities and column diameters. The efficiency of purification was also constant for the Sepabeads FP-PH 12 columns ranging from 16 mm to 113 mm in inner diameter. Effects of the ligand concentration on the adsorption capacity were also studied, and the adsorption capacity increased with an increase in the ligand concentration. These effects resulted in decreasing the required amount of salt to purify SN-07.
TL;DR: In this article, the efficacy of acid production rate (APR) controlled operations of a continuous fermentor supporting the growth of a methylotroph, L3, was experimentally examined.
Abstract: The efficacy of acid production rate (APR) controlled operations of a continuous fermentor supporting the growth of a methylotroph, L3, was experimentally examined. Direct digital control of pH at a constant value allowed for on-line estimation of APR during the fermentation. Two types of APR controlled operations were studied. In the first type of operation, the APR was controlled at a constant value according to a predetermined program by manipulating the feed flow rate to the fermentor. Such an operation effectively stabilized the cell mass productivity of a continuous fermentor subjected to disturbances in the feed nutrient concentration. It resulted in a near complete conversion of methanol to yield a cell mass product with very low amounts of unutilized methanol at both steady state and transient fermentation situations. In the second type of operation, the feed flow rate was manipulated to optimize the steady state value of APR during the fermentation. This method shows promise for on-line steady state optimization of cell mass productivity in a continuous fermentor.
TL;DR: In vitro studies with xylanase showed different temperature optima for activity in presence and in absence of xylan as substrate and a number of temperature and pH optima suggested the multiple nature of xyalanase.
Abstract: The rate of total extracellular xylanase production in Trichoderma reesei, QM 9414, system was affected by temperature and pH. In vitro studies with xylanase showed different temperature optima for activity in presence and in absence of xylan as substrate. Similar behaviour was observed in the pH studies. A number of temperature and pH optima also suggested the multiple nature of xyalanase.
TL;DR: The resulting extract after solid-liquid separation showed lower viscosity and less turbidity than unheated controls, making it more suitable for chromatographic separations.
Abstract: Heat conditioning of cell homogenates of B. cereus and a recombinant E. coli was studied for the isolation of leucine dehydrogenase and alanine racemase, respectively. The strain of E. coli carried the gene of the thermostable alanine racemase from B. stearothermophilus. Activity loss can be minimized (<5%) and aggregation and flocculation of soluble proteins (70–80%) and other cell components can be achieved, depending on temperature, biomass concentration and pH-value. Thereby a 3–6 fold increase in specific activity was obtained. The resulting extract after solid-liquid separation showed lower viscosity and less turbidity than unheated controls, making it more suitable for chromatographic separations.