bluuebunny/crossref_metadata_2025 huggingface dataset:
Cadmium accumulation by immobilized cells of a Citrobacter sp. using various phosphate donors
Authors: Michel L. J. , Macaskie L. E. , Dean A. C. R.
Published: May 2005

Immobilized cells of a Citrobacter species scavenge cadmium with high efficiency from challenge flows containing Cd2+. Metal uptake by the cells in mediated by a cellbound phosphatase which liberates inorganic phosphate from an organic phosphate to precipitate cadmium as cell‐bound metal phosphate. Hitherto glycerol 2‐phosphate has served as the phosphate donor, but for an economic large scale process an inexpensive and readily available phosphate donor is required and the use of alkyl phosphates was investigated. This was limited due to interference by the alcohol simultaneously liberated. An alternative, pulsed process is described whereby alkyl phosphate‐supplemented main pulses interspersed with short alkyl phosphate‐free “recovery” pulses greatly reduced the requirement for glycerol 2‐phosphate. Wider aspects of phosphate donor utilization were also investigated to compare this strain of Citrobacter with a strain previously reported to accumulate lead but not cadmium.
Synthesis and regulation of extracellular β (1–3) glucanase and protease by cytophaga sp. In batch and continuous culture
Authors: Andrews B. A. , Asenjo J. A.
Published: May 2005

Lytic enzyme systems with the ability to break whole cells of yeast are a mixture of several enzymes and virtually all contain β(1–3)glucanases and some protease. It appears that the presence of these two enzyme activities is necessary to break the two layers of the rigid cell wall. The enzyme system of Cytophaga NCIB 9497 has a high activity towards the walls of yeast and also of bacteria. This article describes the production of this extracellular lytic enzyme system in batch and continuous culture—it was found to be inducible. The synthesis and regulation of the two main constituent enzymes, β(1–3)glucanase and protease, have been investigated. The synthesis of β(1–3)glucanase is regulated by bothinduction (by an unknown inducer) and catabolite repression. Highβ(1–3)glucanase activities were obtained in continuous culture at low dilution rates over a narrow range (0.05–0.10 h−1), and there is evidence of the presence of more than one glucanase enzyme. Proteolytic activity appears subject to catabolite repression and made up of the activities of more than one protease enzyme. Productivity and enzyme concentration were increased several fold in continuous culture when compared to batch culture.
Computational algorithms for optimal feed rates for a class of fed‐batch fermentation: Numerical results for penicillin and cell mass production
Authors: Lim H. C. , Tayeb Y. J. , Modak J. M. , Bonte P.
Published: May 2005

Based upon the general characteristics of the optimal feed rate profiles presented in an earlier article, efficient computational algorithms have been developed for fed‐batch fermentation processes described by four or less mass balance equations. These algorithms make computations of optimal substrate feed rate profiles straight forward and simple for various fed‐batch cultures for such products as antibiotics, amino acids, enzymes, alcohols, and cell mass. Numerical examples of penicillin fermentation and bacterial cell mass production are given in detail, illustrating the use of these algorithms.
Kinetic model for the regulation of redox reaction in steroid transformation by Arthrobacter globiformis cells
Authors: Gachok V. P. , Grytsay V. I. , Arinbasarova A. Yu. , Medentsev A. G. , Koshcheyenko K. A. , Akimenko V. K.
Published: May 2005

A kinetic model of hydrocortisone transformation was developed in studies of the kinetics of biochemical systems. The regulatory bases of the model are the biosynthesis of steroid‐transforming enzymes and their activity, the level of endogenous substrates, the respiratory chain activity, and the initial concentrations of reagents. When compared, the experimental data completely coincide with the results of the computer modeling, the coincidence being not only qualitative but also quantitative. It indicates that the model suggested can be used for further studies of other transformations of steroid compounds, as well as for transformation of steroid compounds under close‐to‐biotechnological conditions. The results obtained by means of this model permit one to trace in dynamics the behavior of a number of parameters characterizing the process which is very difficult or not feasible to do in a biochemical experiment. The following was shown: (1) the behavior of the respiratory chain (the reversible transition of its oxidized and reduced forms); (2) the change of the transmembrane potential of hydrogen ions within a far larger stretch of time than is feasible to register in a biochemical experiment; (3) the regulation of the activity of 20β‐hydroxysteroid dehydrogenase and 1, 2‐reductase not only by the change in the level of endogenous substrates, but also by means of their biosynthesis; and (4) the regulatory role of 3‐ketosteroid‐1‐en‐dehydrogenase.
Competitive yeast fermentation with selective flocculation and recycle
Authors: Davis Robert H. , Parnham Charles S.
Published: May 2005

Continuous fermentations were carried out involving competition between two strains of Saccharomyces cerevisiae. One of the strains has a lower specific growth rate and is very flocculent, whereas the fastergrowing strain is nonflocculent. The product stream from the chemostat was fed into an inclined settler where the flocculent strain was partially separated from the nonflocculent strain as a result of the higher sedimentation rate of the flocculent cells. The underflow from the inclined settler, which was concentrated and enriched with flocculent cells, was recycled to the chemostat. When no recycle was used, the fastergrowing, nonflocculent yeast rapidly overtook the culture. With selective recycle, however, the experiments demonstrated that the slower‐growing flocculent yeast could be maintained as the dominant species. A theoretical development is also presented in order to describe the competition between two strains in the bioreactor‐settler system. The concept of selective recycle via selective flocculation and sedimentation offers a possible means of maintaining unstable recombinant microorganisms in continuous fermentations.
Effect of hydrogen acceptors on D‐xylose fermentation by anaerobic culture of immobilized Pachysolen tannophilus cells
Authors: Ligthelm Magdalena E. , Prior Bernard A. , Du Preez James C.
Published: May 2005

The effect of hydrogen acceptors on the kinetic parameters of D‐xylose fermentation under anaerobic conditions was studied in a transient culture of immobilized Pachysolen tannophilus cells. Addition of oxygen to a steady‐state culture resulted in a rapid increase (up to fivefold) in the rates of ethanol production and D‐xylose uptake, but the rate of xylitol production was unaffected. Furthermore, the molar ethanol yield increased from 0.97 to 1.43 in the presence of oxygen. The moles of ethanol produced per moles of oxygen utilized were considerably greater than would be predicted from the stoichiometry of D‐xylose fermentation, which suggests that the organism required oxygen for other functions in addition to its role as a hydrogen acceptor in D‐xylose metabolism. When the artificial hydrogen acceptors acetone, acetaldehyde, and acetoin were added to the culture, the rate of ethanol production increased while the xylitol production rate decreased but the rate of xylose uptake was unaffected. The molar ethanol yields increased from 1.03 to 1.63, 1.43, and 1.24 upon addition of acetaldehyde, acetone, and acetoin, respectively, at the expense of the molar xylitol yields. The hydrogen acceptors sodium acetate, methylene blue, benzyl viologen, phenazine methosulfate, indigo carmine, and tetrazolium chloride had no effect on ethanol production.
Forced‐flow bioreactor for sucrose inversion using ceramic membrane activated by silanization
Authors: Nakajima Mitsutoshi , Watanabe Atsuo , Jimbo Naoyuki , Nishizawa Kouji , Nakao Shin‐ichi
Published: May 2005

A forced‐flow enzyme membrane reactor system for sucrose inversion was investigated using three ceramic membranes having different pore sizes. Invertase was immobilized chemically to the inner surface of a ceramic membrane activated by a silane—glutaraldehyde technique. With the cross‐flow filtration of sucrose solution, the reaction rate was a function of the permeate flux, easily controlled by pressure. Using 0.5 μm support pore size of membrane, the volumetric productivity obtained was 10 times higher than that in a reported immobilized enzyme column reactor, with a short residence time of 5 s and 100% conversion of the sucrose inversion.
Effects of temperature on lactose hydrolysis by immobilized β‐galactosidase in plug‐flow reactor
Authors: Yang Shang‐Tian , Okos Martin R.
Published: May 2005

The hydrolysis of lactose using immobilized β‐galactosidase (from Aspergillus niger) on phenol–formaldehyde resin was studied at temperatures between 8 and 60°C and initial lactose concentrations ranging from 2.5 to 20.0%. A model involving enzyme–galactose complex similar to Michaelis–Menten kinetics with competitive product (galactose) inhibition is suitable to describe the lactose hydrolysis reaction. A small degree of lack of fit between the model and the data was found to be due to the formation of oligosaccharides. Thermal deactivation of lactase follows first‐order reaction mechanism. The effect of temperature on the reaction and the deactivation rate constants follows the Arrhenius relationship. The Oligosaccharide formation was not significantly affected by the temperature when the initial lactose concentration was 5%. A design equation for the plug‐flow immobilized lactase reactor was developed from the reaction and the deactivation kinetics and was used to find the optimal operating temperature. The optimal temperature was found to be dependent on the operating time but not on the lactose concentration or the conversion. The optimal operating temperature is 60°C when operating time is short but is close to 35°C for a long operating time. A preliminary economic analysis indicates that the optimal operating temperature is 43, 38.5, and 33°C when the operating time is 300 days, 1000 days, and infinity, respectively.
Alteration of substrate regulation patterns in glutamate dehydrogenase by enzyme immobilization
Authors: O'Connor Kim C. , Schütz Hans‐Jürgen , Bailey James E.
Published: May 2005

Substrate regulation patterns were changed by covalent binding of bovine liver glutamate dehydrogenase via primary amino groups to CNBr‐ and CH‐activated Sepharose 4B. Lineweaver–Burk plots show that the NAD activation region changed from being abrupt to elongated when the enzyme was immobilized to either support. The elongated region contains two inflection points and resembles substrate activation of several other allosteric oligomers. Glutamate induced varying degrees of abrupt activation in immobilized glutamate dehydrogenase and inhibited the native enzyme. This activation is characterized by an activation threshold, an increase in the apparent dissociation constant, and a correlation between the apparent rate constant and the degree of activation. These three features characterize other glutamate dehydrogenase systems.
Acetic acid production using a fermentor equipped with a hollow fiber filter module
Authors: Park Yong Soo , Ohtake Hisao , Toda Kiyoshi , Fukaya Masahiro , Okumura Hajime , Kawamura Yoshiya
Published: May 2005

The continuous production of acetic acid by Acetobacter aceti M23 was carried out using a fermentor equipped with a hollow fiber filter module. The culture continued for 830 h with various dilution rates, which were changed stepwisely from low to high. The final cell concentration was 21.9 g dry cell/L and the maximum productivity of acetic acid was 12.7 g/L·h for the exit acetic acid concentration of about 50 g/L. The productivity was higher than any literature's values surveyed so far. The cell concentration was 62.8 times and the productivity was 4.6 times as high as those of the fermentor without the filter module. The productivity increased with the increase of dilution rate up to 0.3 h−1. It is interesting to note that the viable cell concentration was kept almost constant about 1.1 × 109 cells/ml in spite of the increase of dilution rate. Use of oxygen‐rich air was indispensable to establish the high productivity of acetic acid.
Optimization of physiological factors for direct saccharification of cassava starch to glucose by Rhizopus oligosporus 145f
Authors: Garg S. K. , Doelle H. W.
Published: May 2005

Direct saccharification of 2.64% cassava starch by Rhizopus oligosporus 145F was attempted under various cultural conditions. Maximum glucose yield of 18.0 g/L culture filtrate was obtained with an initial pH 3.8, 2% (v/v) inoculum of R. oligosporus spores, and an incubation temperature of 45°C in shake flask cultures for 48 h. This concomitantly produced 2.7 g mycelia/100g cassava starch containing 20.2% true protein. The production of glucose and mycelia was accomplished with 92.8% starch saccharification having 67.9% starch to glucose conversion efficiency.
Affinity‐Specific protein separations using ligand‐coupled particles in aqueous two‐phase systems: I. Process concept and enzyme binding studies for pyruvate kinase and alcohol dehydrogenase from Saccharomyces cerevisiae
Authors: Ku Che‐An , Henry Joseph D. , Blair James B.
Published: May 2005

A process using ligand‐coupled particles in aqueous polyethylene glycol‐dextran two‐phase polymer systems was developed to achieve a highly selective, scaleable biochemical separation process. Product protein is bound to the ligand‐coupled particles that quantitatively distribute to the polyethylene glycol‐rich upper phase. Other proteins and contaminants partition preferentially to the dextran‐rich lower phase.

The process offers significant advantages over affinity partitioning here the ligand is coupled to the backbone of a polyethylene glycol polymer. These advantages include a much wider diversity of ligands that can be coupled to particles and more effective confinement of the ligand in the process. Affinity partition with ligands coupled to particles is more amenable to scale‐up than is affinity chromatography. A variety of commercially available Sepharose‐based particles are suitable for this process. Homogenates from Saccharomyces cerevisiae, which is genetically altered to overproduce pyruvate kinase, and Cibacron blue F3G‐A‐coupled Sepharose particles are used as a model system for the process. Binding studies with/without aqueous two‐phase systems show that the formation of a two‐phase system after the adsorption equilibrium is reached does not affect the apparent dissociation constant. Binding of protein to ligand‐coupled particles is more rapid in single‐phase systems than in the polymer two‐phase system. Single‐phase binding eliminates the mass transfer resistance associated with redistribution of product protein from the dextran‐rich bottom phase to the polyethylene glycol‐rich top phase.
Affinity‐Specific protein separations using ligand‐coupled particles in aqueous two‐phase systems: II. Recovery and purification of pyruvate kinase and alcohol dehydrogenase from Saccharomyces cerevisiae
Authors: Ku Che‐An , Henry Joseph D. , Blair James B.
Published: May 2005

The novel approach of using aqueous two‐phase systems for the elution of protein from ligand‐coupled particles is investigated using pyruvate kinase and alcohol dehydrogenase from recombinant Saccharomyces cerevisiae and Cibacron blue F3G‐A‐coupled Sepharose CL6B (Blue‐Sepharose) particles as a model system. The ligand‐coupled particles distribute quantitatively to the polyethylene glycol‐(PEG‐) rich top phase and the recovered enzymes partition selectively to the dextran‐(DEX‐) rich bottom phase. An effective recovery and partial purification of pyruvate kinase and alcohol dehydrogenase from Blue‐Sepharose particles using PEG8000‐DEXT500 aqueous two‐phase systems are demonstrated through a modest increase of salt concentration. The bioselective eluting agent, MgADP, which is useful in chromatographic operations, is not required for the process using aqueous two‐phase systems. Recovery of pyruvate kinase, which is bound to ligand‐coupled particles, in the DEX‐rich bottom phase of aqueous two‐phase systems can be up to 95% in one‐step operations. The mixing time of ligand‐coupled particles with aqueous two‐phase systems is a major controlling variable. The salt concentration, the molecular weight of polymer, and the total volume of aqueous two‐phase systems also influence the recovery of pyruvate kinase from ligand‐coupled particles. The recovered enzymes in the DEX‐rich bottom phase remain biologically stable over a long period of storage time. The concentration of product protein in a reduced volume and the easy separation from ligand‐coupled particles are added advantages of the process using aqueous two‐phase systems. Preliminary studies with goat polyclonal anti‐pyruvate kinase‐coupled Sepharose particles indicate that the process also may be applicable when a high‐affinity ligand such as antibody is used. The experimental results and a theoretical derivation based on equilibrium models for binding/dissociation of ligands and proteins show that the process results in better recovery as compared to that of conventional bulk elution techniques.
The use of cellulases from a β‐glucosidase‐hyperproducing mutant of Trichoderma reesei in simultaneous saccharification and fermentation of wheat straw
Authors: Szczodrak Janusz
Published: May 2005

Conidia of the cellulolytic strain Trichoderma reesei F522 were mutagenized with UV irradiation and N‐methyl|‐N′‐nitro‐N‐nitrosoguanidine (NTG). A visual agar plate detection system was developed, using esculin and ferric ions, to identify mutants of T. reesei with increased β‐glucosidase activity. Selected mutants were tested for production of extracellular cellulases in shake flasks on autohydrolyzed wheat straw as carbon source. The most active mutant V‐7 showed about 6‐times higher activity of β‐glucosidase than the parent strain F‐522, whereas the filter paper degrading and endo‐1,4‐β‐D‐glucanase activities increased by 45% and by almost 31%, respectively. Cellulase preparations obtained from the parent and mutant strains were then used along with Kluyveromyces fragilis cells for ethanol production from ethanol‐alkali pulped straw in the simultaneous saccharification and fermentation (SSF) process. From 10% (w/v) of straw pulp (dry matter), 2.5% (w/v) ethanol was obtained at 43°C after 48 h using cellulase derived from the parent strain of T. reesei. When the β‐glucosidase‐hyperproducing mutant V‐7 was employed, the ethanol yield in the SSF process increased to 3.4% (w/v), the reaction time was shortened to 24 h and no cellobiose was detected in straw hydrolyzates.
A generalized model of plasmid replication
Authors: Satyagal Vasuki N. , Agrawal Pramod
Published: May 2005

A simple model is developed that permits the determination of cellular extrachromosomal DNA content for a large number of host‐plasmid systems. The model incorporates host, vector, and environmental influences on plasmid replication through the use of empirical expressions. The model successfully predicts the plasmid content of many host‐vector systems in a balanced growth situation, both in continuous and batch cultures. Techniques for determining model parameters are also presented. The model parameters, which characterize the effect of plasmid on its own synthesis, are given physical interpretation through the development of a structured model for a particular class of plasmids and subsequent comparison of the predictions of the two models. The simplicity of the model expressions should, in the absence of: (1) discriminatory criteria such as plasmid concentration under transient growth conditions or (2) detailed knowledge on molecular mechanisms of plasmid replication, prove useful in the study of host‐vector systems for genetic engineering applications.
Physiological state control of fermentation processes
Authors: Konstantinov Konstantin , Yoshida Toshiomi
Published: May 2005

In this article a novel approach to the control of fermentation processes is introduced. A “physiological state control approach” has been developed using the concept of representing fermentation processes through the current physiological state of the cell culture. No conventional mathematical model is required for the synthesis of such a control system.

The main idea is based on the fact that during batch, feed‐batch, or even continuous cultivation the physiological characteristics of the cell population, jointly expressed by the term “physiological state”, are not constant but rather variable, which is reflected in expected or unexpected changes in the behavior of the control plant, and which requires flexible alteration of the current control strategy. The proposed approach involves decomposition of the physiological state space into several subspaces called “physiological situations.” In every physiological situation the cell population expresses stable characteristics, and therefore an invariant control strategy can be effectively applied. The on‐line functions of the physiological state control system consist of the calculation of physiological state variables, determination of the current physiological situation as an element of a previously defined set of known physiological situations, switching of the relevant control strategy, and calculation of the control action. Attention is focused on the synthesis of the novel and nonstandard part of the control system – the algorithm for online recognition of the current physiological state. To this end an effective approach, based on artificial intelligence methods, particularly fuzzy sets theory and pattern recognition theory, was developed. Its practical realization is demonstrated using data from a continuous fermentation process for single cell protein production.
Bistat—A novel method of continuous cultivation
Authors: Minkevich I. G. , Yu. Krynitskaya A. , Eroshin V. K.
Published: May 2005

Bistat is the method of continuous cultivation developed on the basis of pH‐auxostat. It provides the stability of cultivation in each point of μ(S) dependence. This article describes the principle of bistat operation, the theory of bistat dynamics, its instrumentation, and some experimental results.
Microbial conversion of β‐ionone by immobilized Aspergillus niger in the presence of an organic solvent
Authors: Sode Koji , Karube Isao , Araki Reiko , Mikami Yoichi
Published: May 2005

Aspergillus niger JTS191 was capable of the conversion of β‐ionone to a mixture of its derivatives that is utilized to an essential oil of tobacco. The authors attempted this microbial conversion in the presence of an organic solvent to improve its reaction rate. The addition of isooctane accelerated the microbial conversion of β‐ionone. It took three days to complete the reaction whereas without isooctane it took more than six days. The addition of isooctane also improved the resistance of A. niger to the antifungal property of β‐ionone. A. niger pellets were immobilized in hydrophobic polymer, PU‐3, and applied for the microbial conversion of β‐ionone. Further improvement of the resistance to the antifungal property of β‐ionone was achieved by immobilization. PU‐3 immobilized A. niger was repeatedly used for microbial conversion of β‐ionone in the presence of isooctane for more than 480 hours.
Novel technique for investigation and quantification of bacteriol leaching by Thiobacillus ferrooxidans
Authors: Bäurtels C.‐C. , Chatzitheodorou G. , Rodriguez‐Leiva M. , Tributsch H.
Published: May 2005

A novel, efficient, and simple technique for the in situ study and quantification of the heterogeneous Bacteriol activity and the Bacteriol degradation of metal sulfides by Thiobacillus ferrooxidans is presented. It consists of exposing an ultrathin (300–2500 Å) metal sulfide layer, FeS2 in the experiments, to Thiobacillus f. grown in Touvinen media and visually following the Bacteriol attack and development of Bacteriol corrosion patterns under a light microscope. The uniform pyrite layer, partially transparent for visible light, permits the optical characterization of Bacteriol attack in remarkable detail. Several open or little understood questions concerning Bacteriol leaching, such as those on the kinetics of adhesion, the interfacial Bacteriol reproduction, the density of surface active bacteria, and the rate and morphology of sulfide degradation can also be studied. The degree of Bacteriol activity can be distinguished on the basis of development of variable sizes of spots and halos around Bacteriol cells produced by light passing through differently sized corrosion pits. The information obtained and identification of microorganisms has additionally been accentuated by immunofluorescence techniques (FA). It is concluded that the described method can be developed as a convenient testing and control technique for use in mine laboratories and bioleaching operations.
The continuous recovery of uranium from biologically leached solutions using immobilized biomass
Authors: Tsezos M. , McCready R. G. L. , Bell J. P.
Published: May 2005

The potential of uranium recovery from the dilute uranium ore bioleach solutions of the Elliot Lake district of Canada was examined using immobilized microbial biomass. Batch and continuous laboratory scale pilot plant experiments were carried out. The results have shown that the immobilized microbial biomass can successfully recover all of the uranium from dilute (less than 300 mg U/L) solutions. The uranium can subsequently be eluted producing a high uranium concentration eluate perhaps exceeding 5000 mg U/L. The biomass maintained its biosorption capacity of about 50 mg U/g over 12 examined successive adsorption‐elution cycles with no apparent indication of failure.
Energetic and rate effects on methanogenesis of ethanol and propionate in perturbed CSTRs
Authors: Smith Daniel P. , McCarty Perry L.
Published: May 2005

Energetic and reaction‐rate interactions between hydrogenic (hydrogen‐producing) and hydrogenotrophic (hydrogen‐consuming) bacteria were investigated in five perturbation experiments performed on steady‐state, mixed‐culture methanogenic CSTRs receiving ethanol, propionate, or both hydrogenic substrates. When a large quantity of propionate was suddenly added to a propionatefed CSTR, P increased to 10−4 atm and propionate oxidation remained energetically favorable. When ethanol was added to a CSTR receiving ethanol, P rose to 6.3 × 10−3 atm within 5 h. In both perturbations, P remained at levels such that oxidation of the hydrogenic substrate remained energetically favorable throughout the transient. Sudden increase in ethanol concentration in the ethanol‐ and propionate‐fed CSTR resulted in an increase in P such that propionate oxidation became energetically unfavorable and was blocked. Propionate utilization resumed when the added ethanol was depleted and P returned to its previous steady‐state levels. Ethanol perturbation of ethanol‐ and propionate‐fed CSTRs led to the formation of reduced products, including n‐propanol and four‐through seven‐carbon n‐carboxylic acids, when P was elevated; these products disappeared after P returned to previous, steady‐state levels. The transformations were consistent with reaction energetics. Reduced product formation may have been a sink for reducing equivalents, as an alternative to oxidation for propionate utilization, as indicated by an electron equivalents balance over the time course of experiments.
Electrophoretic and enzymatic studies on the crude extracellular enzyme system of the cellulolytic bacterium Cellulomonas sp. ATCC 21399
Authors: Poulsen O. M. , Petersen L. W.
Published: May 2005

Cellulomonas sp. ATCC 21399 produced extracellular enzyme activities against Avicel, H3PO4‐swollen Avicel, carboxymethylcellulose, (1‐3, 1‐4)‐β‐D‐heteroglucan, xylan, galactomannan, and amylose drying growth on microcrystalline cellulose. No extracellular cellobiase activity was produced. Crossed immunoelectrophoresis of the crude extracellular enzyme system revealed 15 immunologically distinct immunoprecipitates. The immunoprecipitates of endoglucanase A, endoglucanase B and the xylanase appeared heterogeneous with several optima, whereas the immunoprecipitates of endoglucanase C and the amylase appeared homogeneous. The heterogeneity of endoglucanase A, endoglucanase B and xylanase was also visualized using electrofocusing‐immunoelectrophoresis. Electro‐focusing could resolve the activity against carboxymethylcellulose into six peaks, whereas only one peak of activity against Avicel was observed. The later peak coincided with the major peak of activity against carboxymethylcellulose with isoelectric point between pH 4.0–5.0.
Mode of action of endopolygalacturonase immobilized by adsorption and by covalent binding via amino groups
Authors: Rexová‐Benková L. , Omelková J. , Veruovič B. , Kubánek V.
Published: May 2005

Action pattern of endopolygalacturonase (E.C.3.2.1.15) immobilized by adsorption on porous powdered poly(ethyleneterephthalate) and covalently bound via amino groups on poly(2, 6‐dimethyl‐p‐phenyleneoxide) and poly(6‐caprolactame), respectively, were investigated in suspension and packed columns using polymeric and oligomeric D‐galactosiduronates as substrates. The covalent binding invariably led to a lowering of randomness of degradation of high‐molecular substrates and loss of specificity of (3 + 1) splitting of tetra(galactosiduronic acid), typical of the free enzyme. In the adsorbed endopolygalacturonase the degree of randomness of degradation of D‐galacturonan and Km,app value were dependent on the substrate transfer; the former parameter increased, the later decreased with increasing flow‐rate of the substrate through the immobilized enzyme bed. The action pattern on low‐molecular substrates was not altered. The changes in action pattern of the covalently immobilized endopolygalacturonase are ascribed to sterical limitations resulting from a binding of the enzyme molecule in the proximity of its active site. In endopolygalacturonase bound to the support by hydrophobic interactions external diffusion effects are regarded the factors governing the enzyme action.
Dewatering of biological slurry by using water‐absorbent polymer gel
Authors: Huang Xia , Akehata Takashi , Unno Hajime , Hirasa Okihiko
Published: May 2005

A new concentrating/dewatering process utilizing water‐absorbent polymer gels as dewatering media for biological slurries is proposed. The polymer gel applied to the process should be of porous structure for rapid water‐absorption and of larger size for easier separation of gel from slurry. Poly(vinylmethylether) gel (PVMEG) prepared by γ‐ray irradiation was found to be suitable for the purpose. PVMEG swelled or shrunk reversibly in response to temperature and its transition temperature was 310K. Slurries of different properties were dewatered quite well by applying PVMEG. The water‐absorbability of the gel was unaffected by the properties of organic substances contained in the slurries. An engineering calculation of the proposed dewatering process, which was called “gel dewatering process,” revealed that the process was promising for concentrating/dewatering microbe‐rich slurries in the respect that it would be composed of compact and simple apparatuses and be an energy saving system.
Experimental and simulation studies of multivariable adaptive optimization of continuous bioreactors using bilevel forgetting factors
Authors: Chang Yong K. , Lim Henry C.
Published: May 2005

A multivariable on‐line adaptive optimization algorithm using a bilevel forgetting factor method was developed and applied to a continuous baker's yeast culture in simulation and experimental studies to maximize the cellular productivity by manipulating the dilution rate and the temperature. The algorithm showed a good optimization speed and a good adaptability and reoptimization capability. The algorithm was able to stably maintain the process around the optimum point for an extended period of time. Two cases were investigated: an unconstrained and a constrained optimization. In the constrained optimization the ethanol concentration was used as an index for the baking quality of yeast cells. An equality constraint with a quadratic penalty was imposed on the ethanol concentration to keep its level close to a hypothetical “optimum” value. The developed algorithm was experimentally applied to a baker's yeast culture to demonstrate its validity. Only unconstrained optimization was carried out experimentally. A set of tuning parameter values was suggested after evaluating the results from several experimental runs. With those tuning parameter values the optimization took 50–90 h. At the attained steady state the dilution rate was 0.310 h−1 the temperature 32.8°C, and the cellular productivity 1.50 g/L/h.
The physiology of lactate production by Lactobacillus delbreuckii in a chemostat with cell recycle
Authors: Major Nicolas C. , Bull Alan T.
Published: May 2005

The physiology of lactate production by Lactobacillus delbreuckii NRRL B‐445 in a continuous fermenter with partial cell recycle has been studied and compared with that observed in a conventional chemostat. Partial cell recycle was achieved using a hollow‐fiber ultrafiltration cartridge. The biomass growth yield was reduced in the recycle fermenter while culture viability and the cellular content of polysaccharide, protein, carbon, and nitrogen remained constant, suggesting an enlarged specific rate of glucose consumption for nonanabolic (e.g., maintenance) functions. The volumetric productivity of lactate was enhanced in the recycle fermenter due to the complete utilization of glucose. The yield of lactate from biomass and the molar product ratio, lactate: ethanol plus acetate, decreased with increasing recycle ratio. Enhanced formation of ethanol and acetate occurred in the recycle fermenter although lactate remained the major product. The change in product profile was due to glucose limitation. The specific activity of lactate dehydrogenase remained constant during recycle fermentation. These physiological observations have implications for the future application of cell recycle to production processes.
An adaptive state estimator for detecting contaminants in bioreactors
Authors: Chattaway Thomas , Stephanopoulos Gregory N.
Published: May 2005

An algorithm is presented for detecting the appearance of contaminants during batch or fed‐batch fermentations, using only presently available on‐line measurements. Its adaptive nature enables it to rely on almost no prior knowledge of the real process. The necessary on‐line measurements are total biomass and its production rate; it is also shown how a physical variable such as oxygen uptake can be used alone instead. The algorithm's properties are studied theoretically and through simulations. These were confirmed by on‐line experimental results, obtained with a Yeast culture, both pure and contaminated by a Bacteria. The algorithm does not detect contaminants when none are there, and it also provides a convergent estimate of a pure culture's specific growth rate. Contaminated cultures are recognized by the algorithm, and this detection can be made more or less conservative. After detection, the various estimates may diverge, due to general observability difficulties, though this divergence can itself be monitored. Moreover, the algorithm is easy to tune and its qualitative behavior is quite insensitive to its adjustable parameters. A practical criterion and scheme for implementation are proposed. The generality of the approach, which far exceeds the experimental system used, is finally discussed.
Mass transfer studies using cloned‐luminous strain of Xanthomonas campestris
Authors: Vashitz O. , Sheintuch M. , Ulitzur S.
Published: May 2005

Measurements of mass transfer in a highly viscous pseudoplastic broth, which is typical to Xanthomonas campestris fermentations, are difficult to obtain by conventional methods and little data is available. A novel research method that uses bioluminescence for mass transfer studies has been developed. A plasmid carrying the luminescence operon of marine luminous bacteria is introduced into an industrial bacteria, X. campestris. Besides producing the polysaccharide xanthangum, the bioluminescent X. campestris emits measurable light. Monitoring the luminescence is a simple, noncontaminating nondestructive and very sensitive indicator of the metabolic activity of the culture during fermentation. Energy drain due to bioluminescence is very low; growth rate and polysaccharide production rate are close to those of the wild‐type strain.

Oxygen and substrate mass transfer are determined by inducing step or periodic fluctuations in their concentration and measuring the resultant luminescence response. Oxygen mass transfer coefficients show linear dependence on Reynolds number and an exponential dependence on the average shear rate. Viscosity effect is small at high viscosities but increases rapidly below 10 Pa‐s. The influence of oxygen uptake rate is studied.

Mass transfer of the limiting component (ammonium ions) is analyzed under pulsating feed conditions. The luminescence declines, following a feed pulse, due to energy investment in active transport of ammonium ions through the cell membrane, it regenerates then to its baseline. The relation between mass transfer and luminescence fluctuation is elucidated.
Bacterial growth on lactose: An experimental investigation
Authors: Straight Jeffrey V. , Ramkrishna D. , Parulekar Satish J. , Jansen Norman B.
Published: May 2005

A wild‐type strain of Klebsiella oxytoca growing aerobically in batch culture has exhibited intermittent or oscillatory growth while growing on lactose at concentrations on the order of 1 g/L or less. In two‐substrate experiments, preferred growth on glucose followed by growth on lactose also produced oscillatory growth behavior during the lactose growth phase at lactose concentrations of 1 g/L or less. Only oscillations in cell density have currently been observed. Alkalinization of the medium during growth on lactose indicated the presence of lactose active transport. The observed intermittent growth was reduced or removed during growth on lactose after preferred growth on galactose or in a medium containing 50 mM NaCl. Results suggested that the presence of an intracellular energy source or a sufficient ΔpH buffer may alleviate growth inhibition when transport and growth processes compete for essential energy resources during growth on lactose.
Alcohol adsorption on softwood lignin from aqueous solutions
Authors: Yang Y. , Ladisch M. R. , Ladisch C. M.
Published: May 2005

Lignin prepared by acid and enzyme hydrolysis of a softwood mixture adsorbs acetone, butanol, and other alcohols while showing only a slight uptake of glucose. Adsorption of butanol is independent of temperature in the range of 30‐65°C. The Polanyi theory fits adsorption for the linear alcohols methanol through hexanol with values of AS and Δμ ranging from 2.6 to 26 J mol−1 K−1and −0.8 to −8 kJ/mol. The adsorption capacity is given by Q (g alcohol/g lignin) = KC*. Where C* is the equilibrium alcohol concentration (g/mL), K = εWexp (Δ/R), and εw is the porosity of the lignin (0.23‐0.42 mL/g). The value of the adsorption capacity constant K for n‐butanol ranges from 1.3 to 2.7 mL/g on sorbent containing 26‐72% lignin, while ethanol is 0.5‐0.73, acetone is 0.62‐1.0, and glucose is 0.35. Adsorption is shown to occur through combined hydrophobic and hydrophilic interactions of the alkyl and hydroxyl groups, respectively, of the adsorbate with the lignin. Consequently, for the alcohols methanol to hexanol, we present the capacity constant K[=K(R) + K(OH)] as a sum of an alky! adsorption constant (0.1‐9.5 mL/g) and a hydrophilic (0.40‐0.50 mL/g) contribution. This approach may be applicable to organic acids. Lignin's sorbent properties have potential to moderate product inhibition in the anaerobic acetone‐butanol‐ethanol (ABE) fermentation.
Modeling analysis of an intercalated‐spiral alternate‐dead‐ended hollow fiber bioreactor for mammalian cell cultures
Authors: Brotherton John D. , Chau Pao C.
Published: May 2005

The model analysis of a bioreactor with two intercalated‐spiral sets of hollow fibers with alternated dead ends is presented. Design equations are derived based on a model with two jumped fibers and an approximation of the fluid mechanics with a small fiber radius‐to‐length ratio. The performance of the bioreactor is simulated with and without cell growth utilizing a segregated radial flow model in the extracapillary space. The pressure modulus, the wall Peclet number, the Thiele modulus, and the Monod constant are used as model parameters. The results can be used to assess the proper choice of fiber permeability, fiber length, fiber spacing, and flow velocity.
Comparison of wild‐type and Reg 1 mutant saccharomyces cerevisiae metabolic levels during glucose and galactose metabolism using 31P NMR
Authors: Shanks Jacqueline Vanni , Bailey James E.
Published: May 2005

The reg 1 mutation will allow the expression of a cloned gene on a plasmid under the control of a GAL promoter in the presence of glucose. The metabolism of wild‐type and reg l mutant strains was examined by in vivo 31P nuclear magnetic resonance (NMR) spectroscopy. Transient profiles of glucose 6‐phosphate, fructose 6‐phosphate, fructose 1, 6‐diphosphate, and 3‐phosphoglycerate indicated that glucose was processed differently for the reg 1 strain despite similar cytoplasrnic pH values and ATP levels. Intracellular phosphate became depleted in the transition to quasi‐steady state and limited glycolysis in the reg 1 strain. The glucose uptake step or hexokinase step appears to be altered in the reg 1 strain. The reg 1 strain utilized galactose faster than the wild‐type strain under the conditions used for NMR analysis. These results are consistent with the hypothesis that the REG 1 product operates early in the regulatory circuitry for glucose repression. This study illustrates the usefulness of transient information provided by NMR in understanding changes in the metabolism of genetically manipulated organisms.
The loss of antibody productivity in continuous culture of hybridoma cells
Authors: Frame Kelly K. , Hu Wei‐Shou
Published: May 2005

Two hybridoma lines, HB8178 and AFP‐27, were grown in continuous culture. The concentrations of viable cells as well as those of various nutrients and metabolites reached steady‐state values. The concentrations of either total IgG or antigen‐specific antibody, however, failed to reach steady‐state values but rather continuously decreased over the course of the cultures. The fraction of antibody‐producing cells in the total cellular population also continuously decreased in the AFP‐27 cultures. Comparison of the specific antibody productivity based on either the entire population or the antibody‐producing fraction of the population over time suggests that the decrease in productivity was at least partly due to the occurrence of a nonproducing subpopulation of cells.
Continuous measurement of dissolved H2 in an anaerobic reactor using a new hydrogen/air fuel cell detector
Authors: Pauss A. , Samson R. , Guiot S. , Beauchemin C.
Published: May 2005

A miniature fuel cell, using a hydrophobic Teflon® membrane, designed to continuously measure dissolved H2 in nonbiological media, was tested for use in anaerobic digestion conditions. In water, this detector responds quickly and efficiently to variation of hydrogen concentration in the range from 80 to 770 nM The media used, and the metabolites or products found in anaerobic digestion media, i. e. inorganic carbon and phosphate buffers, formate, acetate, and dissolved methane, did not interfere with the signal of the detector cell. Dissolved hydrogen sulfide did not poison the cell but was detected. In spite of the detector's high sensitivity to hydrogen (about 21,000 times higher for hydrogen than for hydrogen sulfide), interferences can occur in media containing high sulfide levels.

In a methanogenic reactor, the detector cell response to dissolved hydrogen was fast and reliable with time. The observed values ranged values ranged from 2 to 3.5μM. Dissolved hydrogen concentrations were 40 to 70 times higher than values calculated from measured hydrogen partial pressures and Henry's coefficient, suggesting a limitation of the process in the hydrogen transfer from the liquid to the gaseous phase.
Liquid circulation in external‐loop airlift bioreactors
Authors: Kawase Yoshinori
Published: May 2005

A simple model for prediction of liquid velocity in external‐loop airlift bioreactors has been developed. Theoretical correlations for friction factor of gas‐non‐Newtonian two‐phase flows and for liquid velocity in the riser were derived using the concept of an eddy diffusivity. The predictions of the proposed model were compared with the available experimental data for the friction factor and the liquid velocity in the riser of external‐loop airlift contactors. Satisfactory agreement was obtained.
Asymmetric reduction of ketones with resting cells of Sulfolobus solfataricus
Authors: Trincone Antonio , Lama Licia , Lanzotti Virginia , Nicolaus Barbara , De Rosa Mario , Rossi Mosé , Gambacorta Agata
Published: May 2005

The method of resting cells has been of interest in the development of biocatalysts applied to organic reactions.

This article deals with the use of resting cells of a thermophilic archaebacterium Sulfolobus solfataricus, in the asymmetric reduction of acyclic, cyclic, and aromatic ketones. The system allows the continuous regeneration of endogenous coenzyme with the coupled substrate approach. The results indicate that the direction of hydride attack was equatorial on the re face of the carbonyl group of substrates producing (S)‐alcohols with a good optical yield. A convenient system for the reuse of resting cells has been set out to synthesize (S)‐alcohols on a preparative scale.
Oxygen transfer enhancement in aqueous/perfluorocarbon fermentation systems: I. experimental observations
Authors: Junker Beth H. , Hatton T. Alan , Wang Daniel I. C.
Published: May 2005

A new fiber‐optic dissolved oxygen sensing technique was applied to the study of two‐phase aqueous/perfluorocarbon (pfc) dispersions. These dispersions were examined for their oxygen transfer enhancement capability in the absence and presence of an oxygen‐consuming reaction. For the pfc‐in‐water dispersions, oxygen uptake rate (OUR) enhancements were equal both with and without oxygen‐consuming cells present in the aqueous phase. In contrast, for water‐in‐pfc dispersions, OUR enhancements inthe presence of reaction were limited by oxygen diffusion across the aqueous phase droplets. Nevertheless, enhancement factors of 5–10 on an aqueous phase volume basis were obtained in a 75% pfc dispersion.These oxygen transfer enhancements were directly translatable into enhancements in overall fermenter productivity for actual microbial cultivation systems.
Drying of ethanol vapors by adsorption on corn meal
Authors: Hassaballah A. A. , Hills J. H.
Published: May 2005

Experiments have been carried out on a laboratory‐scale adsorber packed with 3.3 kg cornmeal. The effects of varying particle size, feed concentrations and flow rates, and regeneration conditions on the product quality and breakthrough times were investigated. It was found that 85% (w/w) vapor feed gave the best product, and product yields of up to 99.8% (w/w) alcohol were obtained at energy costs as low as 4.0 MJ kg−1. It is suggested how this figure could be improved.