bluuebunny/crossref_metadata_2025 huggingface dataset:
Continuous production of thienamycin in immobilized cell systems
Authors: Arcuri E. J. , Slaff G. , Greasham R.
Published: May 2005

A novel 2‐L bubble column was used to study the continuous, immobilized cell production of thienamycin. Cells of Streptomyces cattleya were immobilized by culturing them in an appropriate growth medium containing 60/80 mesh celite particles. The dilution rate used during the continuous growth phase was 0.2 h−1. This growth phase was terminated upon the development of heavy cell films (100–500 μm thickness), and the medium was replaced with an appropriate thienamycin production medium. The system was then operated in a batch mode until thienamycin production began. At that time, continuous feeding of the production medium was initiated and the influence of medium composition and dilution rate on CO2, NH4, biomass, and thienamycin production investigated. With synthetic production medium, a doubling of the dilution rate from 0.05 to 0.10 h−1 resulted in a doubling of the thienamycin volumetric productivity. Rates of CO2 and NH4 production increased by ca. factors of three and two, respectively. The rate of PO4 utilization also doubled. When the dilution rate was decreased to 0.05 h−1, the rates of CO2 production and PO4 utilization quickly decreased (i.e., within 3 h). The rates of NH4 and thienamycin production also decreased but more slowly (i.e., ca. 100 h after the decrease in dilution rate). With complex production medium, the rates of CO2 production and PO4 utilization appeared to be a direct function of dilution rate at the dilution rates tested. Thienamycin production in this case was not a function of dilution rate. Comparing the synthetic medium with the complex medium at either dilution rate, the volumetric rate of thienamycin production was higher in the system being fed complex medium. However, the specific activity (units thienamycin/g cell/h) observed with complex medium was lower than that observed with synthetic medium. The higher volumetric productivity observed with complex medium was the result of a high cell loading. The above observations will be discussed in terms of control of thienamycin synthesis and film thickness effects.
Synergism of endoenzyme and exoenzyme on hydrolysis of soluble cellulose derivatives
Authors: Fujii Michihiro , Shimizu Masami
Published: May 2005

A kinetic model that represents the reaction of hydrolysis of water‐soluble cellulose derivatives by a mixed endo‐ and exoenzyme system is proposed with the following assumptions: at an early stage of the reaction, endoenzymes split the substrate molecule in order to supply the newly formed nonreducing ends to exoenzymes until the molecular weight of the substrates reaches a low value; after that point, the reaction kinetics obeys only the rate equation of the reaction of the exoenzymes in which the reaction parameters change linearly with decrease of the molecular weight of the substrates. Hydrolysis experiments of soluble cellulose derivatives, carboxymethyl cellulose and hydroxyethyl cellulose, were carried out with endo‐and exoenzymes separated from Trichoderma Koningii cellulase. The critical molecular weight of the substrate, from that point the action of endoenzyme can be neglected, was determined from the experimental data. That was ca. 4000 D. With that value, the model fits well the experimental data. Synergism of both enzymes appears as enhancement of the rate of the reaction at the early stage of the reaction.
Fermentation kinetics of spent sulfite liquor by Saccharomyces cerevisiae
Authors: Safi B. F. , Rouleau D. , Mayer R. C. , Desrochers M.
Published: May 2005

The growth kinetics of the yeast Saccharomyces cerevisiae and the production rate of ethanol have been studied in batch fermentation under anaerobic conditions in a 20‐L fermentor. Two substrates were used in fermentation trials: a synthetic mixture of three fermentable sugars, D‐glucose, D‐mannose, and D‐galactose, and a low‐yield liquor originating from a bisulfite cooking process. The Monod model adequately described the system in relation to the specific growth rate μx and the specific product formation rate μP. Different fermentation parameters (growth rate, substrate utilization, and product formation) were determined for the synthetic mixture and the bisulfite liquor. It was observed that the specific growth rate is much lower in spent sulfite liquor than in a synthetic medium. However, the specific product formation rate remains the same in both media.
Breakthrough behavior of 17.5 mol% water in methanol, ethanol, isopropanol, and t‐butanol vapors passed over corn grits
Authors: Bienkowski P. R. , Barthé A. , Voloch M. , Neuman R. N. , Ladisch M. R.
Published: May 2005

Ground corn is now used in industry as an adsorbent to remove water from ethanol vapors. It is stable and inexpensive at 10 cents/lb (22 cents/kg). For regeneration it requires less than 2000 Btu/gal of 190 proof ethanol processed. If necessary, it could be readily saccharified and fermented into ethanol after use. This renewable resource has further exciting potential as an inexpensive adsorbent for water removal from other alcohols, including methanol, isopropanol, and t‐butanol. Water sorption capacity in a fixed bed, nonisothermal adsorption column appears to be a function of the heat capacity of the non‐adsorbed alcohol vapor, relative to the heat capacity of the corn adsorbent. Methanol, ethanol, isopropanol, and t‐butanol containing 17.5 mol% water gave 105,151, 284, and 358 g anhydrous product/kg adsorbent, respectively, per adsorption cycle. This adsorbent, having operational temperature ranges between 80 and 100°C, is indicated to be of potential utility in solvent recycle processes using these industrially important alcohols. Observed adsorption characteristics are discussed in terms of the alcohol properties of molecular size, heat capacity, and diffusivity. The adsorption mechanism is hypothesized to include transport of water molecules into the structure of adjacent starch molecules present in small spherical bodies (diameter of several microns) immobilized on the surface of the corn grit particles.
Vapor liquid equilibrium behavior of aqueous ethanol solution during vacuum coupled simultaneous saccharification and fermentation
Authors: Roychoudhury P. K. , Ghose T. K. , Ghosh P. , Chotani G. K.
Published: May 2005

The data on ethanol‐water vapor‐liquid equilibrium in the presence of cellulase enzyme, nutrients, yeast, and rice straw indicated a substantial increase in ethanol concentration in vapor phase at reduced pressures. Maximum relative volatility of ethanol in the presence of added components is approximately twice that of a pure ethanol‐water system. The equation correlating the activity coefficient and ethanol concentration in the liquid phase adequately represents the equilibrium behavior.
Photosynthesis in modulated light: Quantitative dependence of photosynthetic enhancement on flashing rate
Authors: Terry Kenneth L.
Published: May 2005

In order to predict the potential benefit associated with mixing devices designed to introduce periodic light modulations in dense cultures of microalgae, it is necessary to develop a quantitative understanding of the relationship between the frequency of the modulations and the resulting photosynthetic efficiency enhancement. To explore this relationship, the photosynthetic rate of cells of Phaeodactylum tricornutum from a dense steady state culture was determined as a function of modulation frequency, intensity of light received, and the proportion of the total cycle period during which the cells were illuminated. At high flash frequencies, the photosynthetic rate was determined by the average intensity received by the cells (full light intensity integration), while at low frequencies the cells responded to the instantaneous intensity (no light intensity integration). Full integration was approached asymptotically with increasing flash frequency. The frequency response could be described by a rectangular hyperbola, and the parameters of this hyperbola were nearly independent of the illumination intensity and the flash proportion. The saturation constant of the hyperbola, at which the response is one‐half of the maximum, was 0.67 Hz.
Use of hexadecyl fractosil as a hydrophobic carrier for adsorptive immobilization of proteins
Authors: Nemat‐Gorgani Mohsen , Karimian Khashayar
Published: May 2005

Fractosil, a porous form of silica, has been used for the preparation of a hydrophobically derivatized carrier for protein immobilization. Interaction of a number of arbitrarily chosen proteins with hexadecyl‐substituted Fractosil has been investigated. Binding of proteins was found to take place with retention of their native properties. Glutamate dehydrogenase, used as a model allosteric protein, was found to retain its catalytic and allosteric properties upon binding to the adsorbent in the form of suspension or column. Positive cooperative interactions for binding of bovine serum albumin and glutamate dehydrogenase to the matrix were observed. These findings are discussed in terms of hydrophobic interactions occurring between various residues of the protein molecules and the hydrophobic ligands in addition to those interactions which may occur with the unsubstituted gel. Results presented on immobilized glutamate dehydrogenase, trypsin, α‐chymotrypsin, α‐amylase, and amyloglucosidase clearly indicate possible potential of the support for continuous catalytic transformations.
Investigation of bacterial growth on mixed substrates: Experimental evaluation of cybernetic models
Authors: Kompala Dhinakar S. , Ramkrishna Doraiswami , Jansen Norman B. , Tsao George T.
Published: May 2005

Cybernetic models, developed earlier by the authors, have been evaluated experimentally for the growth of Klebsiella oxytoca in batch cultures using mixed substrates from glucose, xylose, arabinose, lactose, and fructose. Based entirely on information procured from batch growth on single substrates, the models accurately predict without further parameter fitting, diauxic growth on mixed substrates, automatically predicting the order in which the substrates are consumed. Even triauxic growth on a mixture of glucose, xylose, and lactose is predicted by the model based on single substrate data. Growth on glucose‐fructose mixtures appears to need a slightly modified strategy for cybernetic variables.
Effects of mixing during acid addition on fractionally precipitated protein
Authors: Fisher R. R. , Glatz C. E. , Murphy P. A.
Published: May 2005

Isoelectric fractionation of the two major proteins of soy is characterized. Fractions are acid precipitated and cen‐trifugally collected at pH 6.0 (glycinin) and pH 4.8 (β‐conglycinin). Two extremes in the speed of acid addition (rapid, with no mixing, and slow, via acid dialysis, with complete mixing) are compared to determine their effects on the properties of the precipitate. Total protein yield, fraction composition, and aggregate microstructure do not depend significantly on the method of acid addition. Particle size distribution and hindered settling behavior do differ and are explained using a model of aggregate strength. The rapid acid addition produces larger primary particles, because of higher supersaturation, and yields larger aggregates, because of higher interparticle potential and stronger aggregates. Further aggregation in low‐shear hindered settling is faster for the slowly precipitated aggregate because few of these bonding sites could survive the high‐shear precipitator, whereas more can contribute to aggregation during hindered settling.
Operation and pressure distribution of immobilized cell hollow fiber bioreactors
Authors: Tharakan John P. , Chau Pao C.
Published: May 2005

It has been cited in the literature on hollow fiber systems that pressure gradients persist, and the transmembrane flux of the hollow fiber system is dependent on the pattern of the pressure gradients. The pattern can be used to its advantage in immobilized enzyme systems. However, with immobilized living cell systems, the pressure gradients lead to a nonuniform environment within the hollow fiber cartridge and not necessarily favorable results. This article provides pertinent pressure‐drop data on hollow fiber cartridges which are in flow configurations typical of immobilized cell culture work. The results illuminate operational problems that may arise in the culture of either anchorage dependent or independent cells. Possible solutions with crossflow systems are suggested.
Mixed culture model of anaerobic digestion: Application to the evaluation of startup procedures
Authors: Torre Alberto Dalla , Stephanppoulos Gregory
Published: May 2005

The successful operation of anaerobic digestion depends on the balanced growth of many bacterial species. The functions of the main groups of microorganisms present in a digester have been analyzed and a mathematical model constructed that describes the interactions among the microbial populations and their effect on the digester performance. The model was validated by comparing its predictions with actual digester operation. Several startup procedures were evaluated in the light of the model predictions and improvements on current operational practices suggested in order to minimize startup time.
Alcoholic fermentation of sorghum without cooking
Authors: Thammarutwasik Paiboon , Koba Yojiro , Ueda Seinosuke
Published: May 2005

Sorghum was used as raw material for alcoholic fermentation without cooking. Two varieties of sorghum grown in Thailand, KU 439 and KU 257, contained 80.0 and 75.8% of total sugar. Optimum amount of sorghum for alcoholic fermentation should be between 30 and 35% (w/v) in the fermentation broth. In these conditions 13.0 and 12.6% (v/v) of alcohol could be obtained in 84 and 91.9% yield based on the theoretical value of the starch content from KU 439 and KU 257, respectively.
Simulation study of anaerobic digestion control
Authors: Torre Alberto Dalla , Stephanopoulos Gregory
Published: May 2005

A mixed culture anaerobic digestion model developed previously was applied to the evaluation of several digester control strategies. It was found that pH control by base addition or flow rate manipulation is inadequate. Based on an analysis of digester dynamics, a new control of the total suspended solids concentration at the feed was proposed through the manipulation of the underflow flow rate of the preceeding sedimentation unit. This control was tested in a variety of simulated runs and proved very effective in eliminating most of the usual causes of digester failure.
Effect of organic solvents on the activity of glucoamylase
Authors: Nagamoto H. , Yasuda T. , Inoue H.
Published: May 2005

Hydrolyses of maltose, maltotriose, and soluble starch catalyzed by glucoamylase (Asp. Niger) were carried out in the aqueous solutions of methanol, ethanol, ethylene glycol, and 1,4‐dioxane at 40°C and at the optimum pH in the respective solutions. By the kinetic analysis based on the subsite model, it was shown that the intrinsic rate constant, Kint, was electrostatically affected by the dielectric constant of the hydroorganic solutions. The affinity of the third subsite, A3, which affects the apparent rate constant, K0, was correlated with the ×Gtr's of maltose and amino acid side chains.
Mathematical model of extractive fermentation: Application to the production of ethanol
Authors: Fournier Ronald L.
Published: May 2005

A mathematical model has been developed for the process of extractive fermentation. The model rigorously treats the material balance, reaction kinetics, and liquid–liquid equilibrium relationships. Convergence is promoted through use of the Quasi‐Newton Method. Extractive fermentation is particularly attractive for those bioreactions where the cell growth and product formation is inhibited by the product or other secondary cellular products. The model is illustrated for the production of ethanol. The results show an increase in specific productivity and the ability to process a more concentrated feed. However, volumetric productivity is reduced in the presence of a low capacity solvent.
Structures of steady states of an enzyme reaction in a CSTR
Authors: Byeon Kee Hoh , Chung In Jae
Published: May 2005

Structures at steady states have been investigated for an enzyme reaction in a continuous stirred tank reactor that has a random bi‐uni reaction mechanism, using the imperfect bifurcation theory via singularities. The analysis has shown that two types of singular points exist. One of these points has the two types of transition states characterized by the hysteresis and double‐limit points. It is obtained when the derivative of the steady‐state equation with respect to the bifurcation parameter does not vanish. When the derivative vanishes, the other type of singular point is obtained. This point has the two transition states of hysteresis and bifurcation points.
Periodical batch culture of the immobilized growing fungi Sporotrichum cellulophilum producing cellulase in the nonwoven materials
Authors: Tamada Masao , Kasai Noboru , Kumakura Minoru , Kaetsu Isao
Published: May 2005

The thermophilic fungus Sporotrichum cellulophilum was immobilized with nonwoven materials for cellulase production. The cellulose powder concentration in the medium was an important factor controlling cellulase production. When the cellulose powder concentration in the nonwoven materials was more than 4%, cellulase production was suppressed. The growth of the immobilized fungi depended on the spaces in the nonwoven materials. Immobilized growing fungi were retained by the non‐woven materials, and the supernatant medium did not contain mycelia. The heat stability of the immobilized growing fungus was higher than that of the free fungus. The immobilized fungus gave the same FPA as the free mycelium, but the lag time for cellulase production in the immobilized fungus was longer. It was necessary for the only medium to be changed in order to get the immobilized growing fungus to continue producing cellulase. In this instance there was no difference of lag time in comparison with the free cells, and the supply of cellulose powder and polypepton was reduced to two‐thirds. After 23 exchanges of the medium (2.6 mg cellulose powder/1 cm3 nonwoven materials) FPA value was maintained. The periodic batch culture was continued for 69 days.
Heterogeneous one‐dimensional model for fixed bed enzyme reactors
Authors: Lortie R. , Thomas D.
Published: May 2005

A one‐dimensional model, taking into account the diffusion of substrate between the liquid phase and the solid support, has been used to describe fixed bed enzyme reactors. The equations were solved numerically, and the values of the different parameters were calculated by a nonlinear regression method. The model was applied to different systems. The results are presented and discussed.
Diffusion in κ‐carrageenan gel beads
Authors: Nguyen An‐Lac , Luong J. H. T.
Published: May 2005

Using a well‐mixed and temperature‐led vessel, the diffusion characteristics of various solutes into spherical κ‐carrageenan gel beads were experimentally investigated. The diffusion coefficient of glucose was markedly affected by the glucose concentration and the operating temperature. In all cases the diffusivity obtained was noticeably smaller than that of glucose in pure water. The experimental data also indicated an inverse relationship between the diffusivity and the polymer concentration used in the gel preparation. As well, the glucose diffusivity was affected by the presence of other solutes in the glucose solution. Electrolytes such as ammonium sulfate, KCl, and CaCl2 were observed to enhance the diffusion coefficient. On the other hand, the addition of arginine or bovine serum albumin had an adverse effect on the diffusivity. No diffusion of albumin into the gel beads was observed, and such a solute created a significant mass transfer resistance during the diffusion process.
Deactivation theory
Authors: Henley James P. , Sadana Ajit
Published: May 2005

A general model of enzyme deactivations involving unimolecular processes is introduced. For most mechanisms of this type, the parameters of the general model can be expressed in terms of actual physical parameters. The number of physical parameters that can be determined from the deactivation data cannot exceed the number of independent constants in the general model. When there is an excess of physical parameters, then some parameters must be determined from independent methods of analysis. If this is not possible, then some parameters must be left as lumped parameters or global parameters. The general form of the model can be useful in determining the number of independent, potentially active forms of the enzyme present during deactivation. Some exceptions to the general model are due to higher‐order processes such as dissociation, autolysis, and biological contamination.
Substrate concentration control by dialysis in fermentations of Escherichia coli
Authors: Thompson B. G.
Published: May 2005

A substrate control system based upon dialysis culture techniques has been developed. In fermentations of Escherichia coli where phosphate or sulfate concentrations were controlled, the relation between the apparent specific growth rate, μ, and the phosphate concentration followed Monod kinetics, while the relation between μ and sulfate showed a sharp optimun. The pH of fermentations of E. coli was controlled by dialysis culture techniques without the fluctuations in pH associated with control by direct addition of acid or base.
Reduction of waste product excretion via nutrient control: Possible strategies for maximizing product and cell yields on serum in cultures of mammalian cells
Authors: Glacken M. W. , Fleischaker R. J. , Sinskey A. J.
Published: May 2005

Mammalian cells grown in culture excrete lactic acid and ammonium ions in quantities that may limit growth and reduce product synthesis. Frequent replenishment of the culture medium is often necessary to prevent waste product accumulation which could inhibit cell growth. Since increased medium replenishment results in increased usage of animal serum, the most expensive raw material, excessive production of waste products lowers the cell and product yield on serum, and hence increases production costs. Strategies for reducing the production of lactic acid and ammonium bymammalian cells via controlled addition of glucose and glutamine will be demonstrated. Mathematical relations coupling ammonium and glutamine kinetics will be described. Additionally, a method for automatic on‐line estimation of the cell concentration was developed. This method involves calculating the ATP production rate from the oxygen uptake rate and the lactic acid production rate. Automatic online estimation of the cell concentration is critical if nutrient levels in large‐scale mammaliancell cultures are to be accurately maintained via process control.
Biofilm development in laboratory methanogenic fluidized bed reactors
Authors: Gorris L. G. M. , van Deursen J. M. A. , van der Drift C. , Vogels G. D.
Published: May 2005

Biofilm development on sand with different heterogeneous inocula was studied in laboratory‐scale methanogenic fluidized bed reactors. Both the course of biofilm formation during reactor start‐up and the bacterial composition of newly developed biofilms at steady‐state were found to be similar irrespective of the type of inoculum applied. Biofilm formation proceeded according to a fixed pattern that could be subdivided in three consecutive phases, designated as the lag phase, biofilm production phase, and steady‐state phase. Methanogenic activity and biomass content of the fluidized bed granules were found to be accurate parameters of the course of biofilm formation. More indirect parameters monitored did not give unambiguous results in all instances. The composition of the newly developed biomass as assessed on the basis of potential methanogenic activities on different substrates and of the concentration of specific methanogenic cofactors was consistent with electron microscopic observations.
Studies of Saccharomyces cerevisiae during fermentation—an in vivo electrokinetic investigation
Authors: Bowen W. Richard , Cooke Richard J.
Published: May 2005

An extensive in vivo study of the electrokinetic properties of six strains of the brewing yeast S. cerevisiae has been carried out. The yeasts were cultured under laboratory conditions. They were electrokinetically characterized by the electro‐osmotic dipped cell technique, and data are presented as zeta‐potentials. The effects of pH, fermentation time, successive fermentation cycles, and initial wort density have been established. The electrokinetic properties of an ale yeast which did not function correctly during commercial fermentation have also been examined. The results are discussed in the context of two controversial topics concerning the mechanism of yeast flocculation, the relative importance of yeast cell wall carboxyl and phosphate groups and the influence of wort components.
Growth and death in overagitated microcarrier cell cultures
Authors: Croughan Matthew S. , Wang Daniel I. C.
Published: May 2005

The effects of hydrodynamic forces on cell growth are investigated for animal cells growing on microcarriers. A reduction in net growth was observed with high levels of agitation. DNA measurements indicated that the reduction in net growth was due entirely to cell death, from hydrodynamic forces. No inhibition or enhancement of cell replication appeared to occur with high levels of agitation.
Control of interspecies electron transfer flow during anaerobic digestion: Dynamic diffusion reaction models for hydrogen gas transfer in microbial flocs
Authors: Ozturk Sadettin S. , Palsson Bernhard O. , Thiele Jurgen H.
Published: May 2005

Dynamic reaction diffusion models were used to analyze the consequences of aggregation for syntrophic reactions in methanogenic ecosystems. Flocs from a whey digestor were used to measure all model parameters under the in situ conditions of a particular defined biological system. Fermentation simulations without adjustable parameters could precisely predict the kinetics of H2 gas production of digestor flocs during syntrophic methanogenesis from ethanol. The results demonstrated a kinetic compartmentalization of H2 metabolism inside the flocs. The interspecies electron transfer reaction was mildly diffusion controlled. The H2 gas profiles across the flocs showed high H 2 concentrations inside the flocs at any time. Simulations of the syntrophic metabolism at low substrate concentrations such as in digestors or sediments showed that it is impossible to achieve high H2 gas turnovers at simultaneously low steady‐state H2 concentrations. This showed a mechanistic contradiction in the concept of postulated low H2 microenvironments for the anaerobic digestion process. The results of the computer experiments support the conclusion that syntrophic H2 production may only be a side reaction of H2 independent interspecies electron transfer in methanogenic ecosystems.
Integration of bioconversion and downstream processing: Starch hydrolysis in an aqueous two‐phase system
Authors: Larsson Mats , Arasaratnam Vasanthy , Mattiasson Bo
Published: May 2005

Integration of bioconversion and the first step(s) of down stream processing can be used as a means to increase the productivity of bioprocesses. This integration also gives the possibility to run the bioconversion in a continuous mode. We demonstrate the use of an aqueous two‐phase system in combination with ultrafiltration to accomplish this. Conversion of native starch to glucose by α‐amylase and glucoamylase was carried out in an aqueous two‐phase system in connection with a membrane filtration unit. In this way, a continuous stream of glucose in buffer solution was obtained; the phase‐forming polymers as well as the starch‐degrading enzymes were recycled, and clogging of the ultrafiltration membrane was avoided. The process was carried out continuously in a mixer‐settler reactor for a period of 8 days. The enzyme activities in the top and bottom phases and in the mixing chamber were monitored intermittently throughout the experiment. The optimum pH, temperature, and ionic strength for the activity of the enzyme mixture were determined. The settling time of phase systems containing varying amounts of PEG, crude dextran, and solid starch was studied. The activity and stability of enzyme mixtures was studied both in buffer medium and in the medium containing the polymers. The enzymes were found to be more active and stable in medium containing polymers than in the buffer solutions.
Desorption of cobalt‐laden algal biosorbent
Authors: Kuyucak N. , Volesky B.
Published: May 2005

Following an effective accumulation of cobalt by nonliving algal biomass of Ascophyllum nodosum, the desorption release of the metal from the biosorbent was examined using H2SO4, HCl, NH4OH, KHCO3, EDTA, KSCN, KCl, and CaCl2 solutions. The solution of CaCl2 (0.05M) in HCl appeared to be the best eluant capable of desorbing more than 96% of the sequestered cobalt at the optimum pH 2–3. The optimum solid‐to‐liquid ratio was more than 10 with the cobalt reuptake capacity of the biosorbent undiminished. The effect of temperature on the elution process and the elution rate was not significant up to 60°C. The infrared (IR) spectra of the native and the eluted biomass did not show significant differences. The electron micrographs of the algal biomass taken after washing it with the CaCl2 (0.1M) eluant solution indicated no damage to the cells and cell walls, while strong acid, alkaline, and KSCN treatment resulted in some changes in the cellular structure. The kinetics of the cobalt stripping process was quite rapid. The required contact time for the complete metal removal from the biomass was shorter than 2 h, even for the highest levels of cobalt initially deposited on the biomass.
The mechanism of cobalt biosorption
Authors: Kuyucak N. , Volesky B.
Published: May 2005

Nonliving biomass of the common seaweed Ascophyllum nodosum is capable of accumulating cobalt from aqueous solutions to the extent of 160 mg Co2+/g. Successful desorption of cobalt from the biomass by acidic CaCl2 solutions revealed that the metal uptake phenomenon is reversible, implying physical sorption of cobalt. Chemical and instrumental analysis including electron microscopy, infrared (IR) spectroscopy, X‐ray dispersion and diffraction analysis provided supporting evidence that the biosorption mechanism involves predominantly ion exchange. Alginates of the cell wall (‐COOH groups) play an important role in cobalt binding. Coordination and sorption in the cell wall structure occur simultaneously and rapidly whereas penetration of cobalt into the cell occurs at a lower rate.
Stability of immobilized maltotetraose‐forming amylase from Pseudomonas stutzeri
Authors: Kimura Takashi , Ogata Masafumi , Yoshida Masahiro , Nakakuki Teruo
Published: May 2005

The stability of immobilized maltotetraose (G4)‐forming amylase (1,4‐α‐D‐glucan maltoteraohydrolase, EC 3.2.1.60) from Pseudomonas stutzeri was investigated in both batch and continous processes. The inactivation process of the immobilized enzyme seemed to obey first‐order kinetics, and the immobilized enzyme became more stable when coexisting with 20–30 wt % substrate and calcium ions. From intensive studies on the operational stability in the continuous process, the apparent half‐life of G4 productivity in a constant‐flow system was mainly affected by the reaction temperature, substrate concentration, and initial immobilized enzyme activity. A new factor, immobilized enzyme stability factor fs, was proposed to evaluate the half‐life of the immobilized enzyme system.
Viscous reduction of turbulent damage in animal cell culture
Authors: Croughan Matthew Shane , Sayre Elizabeth S. , Wang Daniel I. C.
Published: May 2005

Animal cells are exposed to turbulent fluid flow in many cell culture processes. If the turbulence in the flow is sufficiently strong, the cells will be damaged or killed by fluid‐mechanical forces. Through an increase in viscosity, the turbulence can be damped and the hydro‐dynamic damage can be reduced. In this article, new experimental results are presented which illustrate the protective effect of thickening agents. The results follow the prediction of a model based on Kolmogorov's theory of universal equilibrium in turbulent flow fields.
Ruthenium red adsorption method for measurement of extracellular polysaccharides in sludge flocs
Authors: Figueroa Linda A. , Silverstein Jo Ann
Published: May 2005

A nondestructive method of measuring extracellular polysaccharides (ECP) in activated sludge floes using Ruthenium Red dye adsorption was developed at the Environmental Engineering Laboratory at the University of Colorado at Boulder. The effects of pH, buffer solution, dye concentration, sludge mass, temperature, and incubation time on dye adsorption was determined. Ruthenium Red dye adsorption to bacterial floes was found to fit a Brunauer–Emmett–Teller (BET) isotherm model. Of the other environmental conditions in the system, pH was found to have the strongest effect on dye adsorption to bacterial flocs. The amount of extra cellular polysaccharides (ECP) measured by Ruthenium Red adsorption was compared with extracellular polysaccharides measured by two chemical extraction methods. Of all methods considered Ruthenium Red dye adsorption measured the highest amount of extracellular polysaccharide with the lowest amount of bacterial cell disruption. Thus, Ruthenium Red dye adsorption was more effective than extraction procedures for measurement of extracellular polysaccharides in activated sludge flocs.
Tetracycline production with sweet potato residue by solid state fermentation
Authors: Yang Shang‐Shyng , Ling Meei‐Yueh
Published: May 2005

For saving energy in antibiotic production and reducing the amount of agricultural wastes, solid state fermentation was used in this study to produce tetracycline with sweet potato residue by Streptomyces viridifaciens ATCC 11989. It was found that the optimal media for tetracycline production were sweet potato residue 100 g, organic nitrogen (rice bran, wheat bran, or peanut meal) 20 g, (NH4)2SO4 2.4 g, KH2PO4 0.4 g, CaCO3 1.8 g, NaCl 0.6 g, MgCl2 0.8 g, soluble starch 10 g, methionine 0.2 g, histidine 0.8 g, and monosodium glutamate 1.6 g with initial moisture content 68–72%, and initial pH 5.8–6.0. Each gram of dry weight substrate was inoculated with 1.0 × 108 conidia and incubated at 26°C for 5–7 days, producing 4720 μg of total tetracycline equivalent potency. When incubated at 26°C with the initial moisture content 68%, the conidia in solid media germinated on the second day, mycelia grew abundantly on the third day and reached stationary phase on the sixth day. The antibiotic production was consistent with the morphogenesis of S. viridifaciens: activity could be detected on the third day, had the maximal potency on the sixth day, and decreased slightly on the tenth day. (11‐3‐88 tly).
Biological phenol degradation in a gas‐liquid‐solid fluidized bed reactor
Authors: Wisecarver Keith D. , Fan Liang‐Shih
Published: May 2005

Biological phenol degradation was performed experimentally in a gas‐liquid‐solid fluidized bed bioreactor using a mixed culture of living cells immobilized on activated carbon particles. A comprehensive model was developed for this system utilizing double‐substrate limiting kinetics. The model was used to simulate the effects of changing inlet phenol concentration and biofilm thickness on the rate of biodegradation for two different types of support particles. The model shows that gas‐liquid mass transfer is the limiting step in the rate of phenol biodegradation when the phenol loading is high.
Solubilization of fish proteins using immobilized microbial cells
Authors: Venugopal V. , Alur M. D. , Nerkar D. P.
Published: May 2005

Cells of Bacillus megaterium, Aeromonas hydrophila, and Pseudomonas marinoglutinosa were immobilized in calcium alginate. The immobilized cells secreted protease when held in fish meat suspension in water. The enzyme synthesis by the entrapped cells was supported by small amounts of soluble nutrients present in the meat. The secreted protease solubilized the fish meat, solubilization being optimum at pH range of 7.5 to 9.5 and at 50°C. Under these conditions immobilized B. megaterium was most efficient giving 30% solubilization of the meat, followed by A. hydrophila (18%), while immobilized P. marinoglutinosa was less effective. The optimum ratio of fish meat to beads was about 4:3 for B. megaterium and A. hydrophila. The beads had a storage life of 30 days at 4°C. The results suggested potential for use of immobilized microbial cells having extracellular protease activity to enhance solubility of waste proteins. A prototype reactor with beads holding assembly was fabricated which could recover the beads from the meat slurry after the treatment.
Mechanism of thermoinactivation of immobilized glucose isomerase
Authors: Volkin David B. , Klibanov Alexander M.
Published: May 2005

Irreversible thermoinactivation of immobilized glucose isomerase from Streptomyces olivochromogenes has been mechanistically investigated at the pH‐optimum of enzymatic activity (pH 8.0). Ligands (high fructose corn syrup and the competitive inhibitor xylitol) greatly stabilize the immobilized enzyme at high temperatures. At 90°C in the presence of 2M xylitol, irreversible inactivation of immobilized glucose isomerase is caused by deamidation of its asparagine/glutamine residues. On the basis of the data obtained, it appears that the time‐dependent decay of glucose isomerase activity in industrial bioreactors is brought about by oxidation of the enzyme's cysteine residue and/or heat‐induced deleterious reactions with high fructose corn syrup or its impurities.
Selective adsorption/desorption of nucleic acids on submicron‐sized polymeric particles
Authors: Kim Chan Wha , Rha ChoKyun
Published: May 2005

DNA can be removed or separated by the selective adsorption/desorption on positively charged submicronsized polymeric particles (SSPP). The selective adsorption of DNA, in the presence of protein, on positively charged SSPP was accomplished by increasing the concentration of potassium phosphate or sodium phosphate. The adsorption of DNA was not affected by the concentration of potassium phosphate or sodium phosphate up to 1.2M. On the other hand, the adsoprtion of a protein (bovine serum albumin) was completely impeded by 170mM potassium phosphate. DNA adsorbed on SSPP could be desorbed by increasing the concentration of NaCl or KCl, thus it can be recovered. DNA desorbed from SSPP when the concentration of NaCl or KC was higher than 0.6M. A complete desorption of DNA was achieved at the concentration of NaCl or KCl above 1.2M.
Surface effects of solvents in hydrolysis of water‐soluble lipids by candidal lipase
Authors: Uçar Tamer , Ekiz H. Ibrahim , Caglar M. Arif
Published: May 2005

In the study of hydrolysis of tributyrin by the lipase of Candida cylindracea, it is shown that initial rates of hydrolysis are directly proportional to the amount of enzyme adsorbed at the substrate‐water interface. As a consequence of understanding the role of the physical state of the substrate in aqueous reaction media, it was hypothesized that the inclusion of synthetic (nonsubstrate) surfaces into the reaction media may enhance the hydrolysis rate of simple liquid lipids which are partly soluble in water, like triacetin. Nonpolar n‐hydrocarbons having 5–11 carbon atoms were used to create interfaces in the hydrolysis of triacetin in the soluble range. All of the C5‐C11 hydrocarbons showed an activating effect. For quantitative evaluation of the effects of n‐hydrocarbons, n‐heptane was chosen as the model n‐hydrocarbon. Interrelations between the reaction kinetics and adsorption of the enzyme at the n‐heptane‐water interface were experimentally determined by the use of the same in‐line filtration device used for the tributyrin‐water system. At 35°C and pH 6 the relative values of the rate constants for the decomposition of enzyme‐interface‐substrate complexes were calculated as 12 and 1 for the tributyrin and n‐heptane‐triacetin systems, respectively. The nature of activation at the solvent surfaces were accounted for by a kinetic model which assumes simultaneous adsorption of enzyme and triacetin molecules at the n‐heptane‐water interface. Making use of the proposed model, the value of a the apparent Michaelis constant for the soluble triacetin‐n‐heptane system at constant n‐heptane concentration, 2 vol %, was calculated as 0.044 mol/L.
Acetone–butanol–ethanol (ABE) fermentation in an immobilized cell trickle bed reactor
Authors: Park Chang‐Ho , Okos Martin R. , Wankat Phillip C.
Published: May 2005

Acetone–butanol–ethanol (ABE) fermentation was successfully carried out in an immobilized cell trickle bed reactor. The reactor was composed of two serial columns packed with Clostridium acetobutylicum ATCC 824 entrapped on the surface of natural sponge segments at a cell loading in the range of 2.03–5.56 g dry cells/g sponge. The average cell loading was 3.58 g dry cells/g sponge. Batch experiments indicated that a critical pH above 4.2 is necessary for the initiation of cell growth. One of the media used during continuous experiments consisted of a salt mixture alone and the other a nutrient medium containing a salt mixture with yeast extract and peptone. Effluent pH was controlled by supplying various fractions of the two different types of media. A nutrient medium fraction above 0.6 was crucial for successful fermentation in a trickle bed reactor. The nutrient medium fraction is the ratio of the volume of the nutrient medium to the total volume of nutrient plus salt medium. Supplying nutrient medium to both columns continuously was an effective way to meet both pH and nutrient requirement. A 257‐mL reactor could ferment 45 g/L glucose from an initial concentration of 60 g/L glucose at a rate of 70 mL/h. Butanol, acetone, and ethanol concentrations were 8.82, 5.22, and 1.45 g/L, respectively, with a butanol and total solvent yield of 19.4 and 34.1 wt %. Solvent productivity in an immobilized cell trickle bed reactor was 4.2 g/L h, which was 10 times higher than that obtained in a batch fermentation using free cells and 2.76 times higher than that of an immobilized CSTR. If the nutrient medium fraction was below 0.6 and the pH was below 4.2, the system degenerated. Oxygen also contributed to the system degeneration. Upon degeneration, glucose consumption and solvent yield decreased to 30.9 g/L and 23.0 wt %, respectively. The yield of total liquid product (40.0 wt %) and butanol selectivity (60.0 wt %) remained almost constant. Once the cells were degenerated, they could not be recovered.
Diffusivity of oxygen into carriers entrapping whole cells
Authors: Sun Yan , Furusaki Shintaro , Yamauchi Aizo , Ichimura Kunihiro
Published: May 2005

The effective diffusivity of oxygen, De, in Ca‐alginate and PVA–SbQ gels was measured using a two‐chamber vessel with a membrane between the two chambers. The effect of cell density, Cc, on De in Ca‐alginate gels was studied. The effective diffusivity of oxygen decreased with increasing cell density, to Cc = 170 kg dry cells/m3 gel. The dependency of De on cell density was discussed in terms of a random‐pore model. The model correlated well with experimental data, i.e., kDe/D0 = 0.86(1 − 1.47 × 10−3 Cc)2. Here, k is the partition coefficient, and D0 is diffusivity in water.
Optimization of fed‐batch penicillin fermentation: A case of singular optimal control with state constraints
Authors: San Ka‐Yiu , Stephanopoulos Gregory
Published: May 2005

The determination of the optimal feeding profile of a fed‐batch fermentation requires the solution of a singular optimal control problem that is often complicated by constraints imposed on the state variables. Such constraints can be a maximum allowable biomass concentration beyond which oxygen transfer is severely limited or maximum substrate concentration to avoid side reactions. Due to these state constraints and the singular nature of the problem, complete solutions are especially hard to obtain and almost nonexistent in the literature. In this work the feed concentration is employed as the control variable in a solution approach that first determines the optimal reactor substrate concentration and subsequently solves for the feed concentration profile that results in the optimal reactor profile. Calculations for the fed‐batch penicillin fermentation indicate sharp increases in productivity over frequently employed strategies.
ESR investigations of free and immobilized glutamate dehydrogenase
Authors: O'Connor Kim C. , Bailey James E.
Published: May 2005

The structure of bovine liver glutamate dehydrogenase was examined with 2,2,6,6‐tetramethyl‐4‐oxopiperidine‐1‐oxyl (TEMPO I) and 4‐((4‐(chloromercurio)benzoyl) amino)‐2, 2, 6, 6‐tetramethyl‐1‐piperidinyloxy (TEMPO II). ESR spectra from TEMPO I show that enzyme structure in the vicinity of this spin label was not distorted during immobilization to a Sepharose support. Deactivation studies with pyridoxal 5′‐phosphate indicate that immobilization did not expose additional binding sites to TEMPO I. Spectra from TEMPO II reveal that immobilization profoundly altered conformational change induced by α‐ketoglutarate and suppressed that induced by GTP and NADPH. This structural investigation provides insight into the altered kinetic properties of Sepharose‐immobilized glutamate dehydrogenase and suggests a fundamental difference between monomers and allosteric oligomers in their structural response to immobilization.
Modified extended aeration process for removal and recovery of cadmium from wastewaters
Authors: Lowe William L. , Gaudy Anthony F.
Published: May 2005

It has been reported in the literature that several microbial species have a considerable sorption capacity for heavy metals. Work herein reported, accomplished using a heterogeneous microbial population developed in a modified extended aeration activated sludge process, indicates sorption capabilities as good as, or better than, those for individual microbial species. The process herein described may have several advantages over pure or controlled culture processes and it offers the possibility for reuse of organic matter needed to regenerate metal‐sorbing biomass, as well as autodigestion of excess biomass. The work also indicates that acclimation to high levels of a specific heavy metal (Cd) does not confer acclimation to another heavy metal (Cu).
Gas–liquid dispersion with dual Rushton impellers
Authors: Hudcova V. , Machon V. , Nienow A. W.
Published: May 2005

Aerated and unaerated power consumption and flow patterns in a 0.56 m diameter agitated vessel containing water with dual Rushton turbines have been studied. Under unaerated conditions with a liquid height‐to‐diameter ratio of 2, an impeller spacing of 2 to 3 times the impeller is required for each to draw an amount of power equal to a single impeller. For aerated conditions, if a similar spacing is used, equations for the flooding‐loading transition and for power consumption for a single Rushton impeller can be extended relatively easily to dual systems. All results for this spacing are explained by reference to bulk flow patterns and gassed‐filled cavity structures and the proportion of sparged gas flowing through the upper impeller is also estimated. Such a spacing is generally recommended since it maximizes the power draw and hence the potential for oxygen mass transfer. Data are presented for other spacings but the results do not fit in easily with single agitator studies because strong impeller‐impeller flow pattern interactions occur.