bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractA 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

AbstractContinuous 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractSubstrate 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

AbstractThe 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

AbstractDirect 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

AbstractA 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

AbstractThe 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

AbstractConidia 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

AbstractA 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

AbstractIn 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

AbstractBistat 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

AbstractAspergillus 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

AbstractA 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

AbstractThe 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.