bluuebunny/crossref_metadata_2025 huggingface dataset:
An assessment of the role of physiological adaptation in the transient response of bacterial cultures
Authors: Daigger Glen T. , Grady C. P. Leslie
Published: December 2004

The RNA‐limiting theory of transient response states that the primary physiological adaptation which occurs when microbial cultures are grown at specific rates less than their maximum is a decrease in the cellular level of RNA. It predicts that, as a result of this decrease, the response of the culture to a shift‐up in growth rate will be limited by its RNA level. In order to test the RNA‐limiting theory and to investigate the role physiological adaptation in transient response, experiments were performed in which steady‐state chemostat cultures of Pseudomonasputida grown at various specific rates were transferred to batch reactors containing sufficient carbon source (L‐lysine) and nutrients to remove all external growth restrictions. Samples were collected during the subsequent transient period for determination of the macromolecular composition and the maximum instantaneous oxygen uptake rate. The results indicated that, while decreases in the RNA level did significantly affect the nature of the transient response, other unidentified components varied with the steady‐state specific growth rate at which the culture had been grown prior to the shift‐up and that the levels of those components affected the nature of the subsequent transient response. This implies that the RNA‐limiting theory is inadequate for describing the transient responses of cultures grown over a wide range of specific growth rates.
Technology advances for continuous compression milling pretreatment of lignocellulosics for enzymatic hydrolysis
Authors: Tassinari Thomas H. , Macy Charles F. , Spano Leo A.
Published: December 2004

The feasibility of a continuous compression milling pretreatment process for the enzymatic hydrolysis of lignocellulosics has been demonstrated. Pretreatment efficiency was improved significantly by adjustment of feedstock moisture content prior to milling and/or increasing the roll pressure on the feedstock. Optimum moisture contents for newspaper (24%). corn stover (17%), popular (12–20%) were determined. Sugar Yields of 48% were obtained from air‐dried newspaper after six passes through even‐pressure rolls and the specific energy input was 0.21kW h/lb. The Effect of roll speed on enzymatic hydrolysis improvement was constant over a roll speed range of from 30–110 ft/min (65 rpm). Enzymatic hydrolysis results from commercial‐scale pretreatment of moist newspaper processed at 6 tons/h/ correlated well with laboratory mill data while energy consumption was 26% less.
Utilization of the “complex method” to optimize a fermentation process
Authors: Saguy Israel
Published: December 2004

The complex method has been applied to maximize the profit of a fermentation process. The optimization method is based on sequential search technique and may be implemented in most process which can be stimulated. Utilizing the derived optimal value of the controllable variables (the concentration of glucose, soybean meal, phosphate, and salt; agitation and aeration rates; inoculum size; and fermentation duration) resulted in a substantial profit increase.
Ethanol production by extractive fermentation
Authors: Minier M. , Goma G.
Published: December 2004

The ideal method to produce a terminal metabolite inhibitor of cell growth and production is to remove and recover it from the fermenting broth as it formed. Extractive fermentation is achieved in the case of ethanol production by coupling both fermentation and liquid‐liquid extraction, The solvent of extraction is 1‐dodecanol (or a mixture 1‐dedecanol, 1‐tetradecanol); study of the inhibitory effect of primary aliphatic alcohols of different chain lengths shows that no growth is observed in the presence of alcohols which have between 2 and 12 carbons. This effect is suppressed when the carbon number is 12 or higher. A new reactor has been used–1 pulsed packed column. Pulsation is performed pneumatically. Porous material used as a package adsorbs the cells. The fermentation broth is pulsed in order to (1) increase the interfacial area between the aqueous phase and the dodecanol, (2) decrease gas holdup. Alcoholic fermentation, performed at 35°C on glucose syrup, permits the total utilization of glucose solution of 409 g/L with a yeast which cannot–in classical process– completely use solutions with 200 g/L of glucose. The feasibility of a new method of fermentation coupling both liquid‐liquid extraction and fermentation is demonstrated. Extension of this method is possible to any microbial production inhibited by its metabolite excretion.
Immobilization of Nitrosomonas europaea cells with polyelectrolyte complex
Authors: Kokufuta Etsuo , Matsumoto Wataru , Nakamura Isei
Published: December 2004

Cell immobilization with polyelectrolyte complex prepared from strongly polyacidic and polybasic ions was investigated for cells from Nitrosomonas europaea (ATCC 25978). Trimethylammonium glycol chitosan (TGCI) and potassium poly(vinyl‐alcohol) sulfate (KPVS) were used. The immobilization was carried out by directly mixing both polymer solutions with the culture broth: An excess of TGCI was first added to the culture broth to aggregate the cells, and then KPVS was added to form the complex with the excess TGCI and to entrap the aggregates with the resulting complex. From physiocochemical studies on the cell aggregation, the mechanism can be interpreted in terms of the adsorption of polyion caused by the salt linkages of the ionizable groups on the cell surface. The result of an electron microscopic observation showed that the cells are situated in the pores and on the surface of the complex support. When the immobilized cells were incubated in a medium buffered by phosphate and containing ammonium sulfate, a considerable amount of nitrite was formed; this was shown to be caused by the entrapped cells and also those cells released from the support and grown in the medium. The ammonia‐oxidizing activity was retained even after a total of 200 h of incubation in a batch reactor. No deformation of the complex support was observed.
The effect of methylacrylate on the activity of glucomylase immobilized on granular polyacrylonitrile
Authors: Handa Takashi , Hirose Akira , Yoshida Shoji , Tsuchiya Haruo
Published: December 2004

Glucoamylase was immobilized on granular polyacrylonitrile (PAN) and the optimum condition in its immobilization reaction was determined. The effect of the ratio of the imidoester and methylester to the total cyanogen on the activity of the immobilized enzyme was studied. The activity of the immobilized enzyme increased in proportion to the molar number of imidoester and decreased with that of methylester. The Km and Vm values of immobilized glucoamylase which were prepared at various conditions of immobilization were determined. There were opposite trends in KmS between glucoamylase immobilized on imidoester‐rich support and immobilized on methylester in the support, evidenced as functions of temperature. This suggests that opposite charges in the support, produced by heat deformation of PAN by hydrolysis of methylester, were an influence on the apparent Km of immobilized glucoamylase, besides the diffusional limitation.
Large‐scale mammalian cell culture: Design and use of an economical batch suspension system
Authors: Tolbert William R. , Schoenfeld Richard A. , Lewis Charles , Feder Joseph
Published: December 2004

Large‐scale mammalian cell culture in the absence of antibiotics requires stringent conditions of sterility for all vessels, procedure, and systems used. Application of existing fermentation technology suffers from the differences between mammalian and bacterial cultures. Relatively simple and inexpensive 100‐L vessels have been designed specifically for medium storage and antibiotic‐free mammalian cell culture. These vessels are portable and sterilized in a 2 × 3 × 5 ft conventional or VACUMATIC autoclave. They consist of 30‐gal 316 stainless‐steel sanitary process drums whose heads have been modified to meet the rapid pressure changes that occur during autoclaving. The vessels incorporate systems for aseptic introduction and removal of both liquids and gases required for inoculation, growth, and harvesting of cell suspensions. A two‐disk vibromixer is used for agitation with inoculation at a laminar flow hood and incubation in a warm room. These vessels have been used for culture of one rat and eight human tumor lines for over 2 × 105 L of suspension.
Stabilization of waste‐activated sludge through the anoxic‐aerobic digestion process
Authors: Hashimoto Susumu , Fujita Masanori , Terai Kazuhiro
Published: December 2004

During the aerobic digestion process, the nitrogen which had been embedded in the activated sludge is solubilized to form ammoniacal and nitric nitrogen which are in turn transferred to the liquor and cause the increase of nitrogen loading in the sewage treatment plant. In this study, the anoxic‐aerobic sludge digestion system which is a modified form of the conventional aerobic sludge digestion is made up of aerobic and anoxic tanks and are designed to remove both the volatile suspended solids and the total nitrogen (TN) simultaneously. The removal efficiencies of both VSS and TN were investigated by feeding waste‐activated sludge continuously and semicontinuously. The maximum percent reduction of both VSS and TN was achieved at a Qr/Qs ratio of 2 in the continuous process. The semicontinuous process was used to improve the nitrogen removal efficiency further. In the semicontinuous process, the VSS reduction efficiency as well as the nitrogen removal efficiency increased remarkably under a constant Qr/Qs ratio of 2. This process also achieved a VSS reduction efficiency higher than the aerobic digestion process (control). It was suggested that the additional anoxic tank enhanced the sludge digestion. Furthermore, the anoxic‐aerobic digestion system can be applied to other treatment media like the primary sludge, industrial sludge, animal manure, etc.
Solubility of plasma proteins in the presence of polyethylene glycol
Authors: Haskó Ferenc , Vaszileva Roza , Halász László
Published: December 2004

The solubility of plasma proteins was studied at various pH as a function of polyethylene glycol concentration. Computer analysis of precipitation curves permitted equations to be derived. The equations describe the relationship between protein solubility and polyethylene glycol concentration. The analysis of the equations furnished further data for the validity of the displacement theory.
A study of acetic acid production by immobilized Acetobacter cells: Product inhibition effects
Authors: Ghommidh C. , Navarro J. M. , Messing R. A.
Published: December 2004

Acetobacter living cells were immobilized by adsorption onto a ceramic support. The effects of acetic acid inhibition have been studied in a fixed‐bed pulsed‐flow reactor. Provided that sufficient oxygen was available, the concentration of acetic acid was found to be independent of the flow rate. Damped oscillations of acetic acid concentration were observed after step changes in dilution rate. The theoretical model developed from steady‐state data was successful in predicting the experimental dynamic behavior of the reactor.
Adsorption of cellulase on cellulose: Effect of physicochemical properties of cellulose on adsorption and rate of hydrolysis
Authors: Lee Sun Bok , Shin H. S. , Ryu Dewey D. Y. , Mandels M.
Published: December 2004

In the cellulase–cellulose reaction system, the adsorption of cellulase on the solid cellulose substrate was found to be one of the important parameters that govern the enzymatic hydrolysis rate of cellulose. The adsorption of cellulase usually parallels the rate of hydrolysis of cellulose. The affinity for cellulase varies depending on the structural properties of cellulose. Adsorption parameters such as the half‐saturation constant, the maximum adsorption constant, and the distribution coefficient for both the cellulase and cellulsoe have been experimentally determined for several substrates. These adsorption parameters vary with the source of cellulose and the pretreatment methods and are correlated with the crystallinity and the specific surface area of cellulose substrates. The changing pattern of adsorption profile of cellulase during the hydrolysis reaction has also been elucidated. For practical utilization of cellulosic materials, the cellulose structural properties and their effects on cellulase adsorption, and the rate of hydrolysis must be taken into consideration.
Immobilized enzymes: Electrokinetic effects on reaction rates under external diffusion
Authors: Kalthod Dilip G. , Uckenstein Eli
Published: December 2004

The rates of reactions catalyzed by enzymes immobilized on a nonporous solid surface have been computed employing a Nernst film model. The Nernst‐Planck equations for the transport of the charged substrate and product species in the film and the Poisson equation for the distribution of electrical potential are solved numerically with the appropriate boundary conditions. The electrical charge at the surface is assumed to arise from the dissociation equilibria of the acidic and basic surface groups of the enzyme. The pH at the surface affects both the surface charge as well as the intrinsic kinetics of the enzyme‐catalyzed reaction. Factors which determine the pH at the surface include the pH in the bulk solution and the release of H+ ions in the enzyme‐catalyzed reaction. The latter causes a lowering of pH at the surface, causing the reaction rate to differ from that computed assuming an equilibrium distribution of electrical potential. Another kind of nonequilibrium contribution is caused by unequal charges or diffusivities of the substrate and products, which results in a diffusion potential being set up. Two moduli are introduced to evaluate the significance of the reaction‐generated lowering of pH and the diffusion potential effect. The effect of changing various parameters, e.g., reaction rate constant, substrate concentration, enzyme concentration, pH, etc., on the overall reaction rate are studied.
Effect of mass transfer in a recirculation batch reactor system for immobilized penicillin amidase
Authors: Park Jong M. , Choi Cha Y. , Seong Baik L. , Han Moon H.
Published: December 2004

The effect of external mass transfer resistance on the overall reaction rate of the immobilized whole cell penicillin amidase of E. coli in a recirculation batch reactor was investigated. The internal diffusional resistance was found negligible as indicated by the value of effectiveness factor, 0.95. The local environmental change in a column due to the pH drop was successfully overcome by employing buffer solution. The reaction rate was measured by pH‐stat method and was found to follow the simple Michaelis‐Menten law at the initial stage of the reaction. The values of the net reaction rate experimentally determined were used to calculate the substrate concentration at the external surface of the catalyst pellet and then to calculate the mass transfer coefficient, kL, at various flow rates and substrate concentrations. The correlation proposed by Chilton and Colburn represented adequately the experimental data. The linear change of log jD at low log NRe with negative slope was ascribed to the fact that the external mass transfer approached the state of pure diffusion in the limit of zero superficial velocity.
Pentosan hydrolysis in a concentrated slurry system
Authors: Horwath J. A. , Mutharasan R. , Grossmann E. D.
Published: December 2004

Pentosan hydrolysis at low aqueous liquid‐to‐biomass ratios (2.5–15 mL/g) with sulfuric acid as the catalyst is studied in the temperature range of 125–155°C. To facilitate heat transfer and mixing a second insoluble oil is added to the reaction mixture. It is found that even at high slurry concentrations, the reaction is the rate‐controlling step. In addition, such systems give higher pentosan yields compared with dilute slurry systems. This is explained using the concept of acid loading which is defined as the acid present per unit mass of biomass.
Adsorption of radium‐226 by biological origin absorbents
Authors: Tsezos M. , Keller D. M.
Published: December 2004

Selected samples of waste microbial biomass used in industrial fermentation processes and wastewater biological treatment plants have been studied for their radium biosorption ability from aqueous solutions. Equilibrium biosorption isotherms have been used to quantify the radium uptake capacity of the various types of biomass which were also compared to two types of activated carbon. Solution pH affected the observed uptake significantly. In general, the biomass types that showed appreciable sorption capacity exhibited maximum uptake between pH 7 and 10. The uptake was reduced considerably at pH 4 and little or no uptake was observed at pH 2. Radium biosorptive uptake capacities of the order of 4.5 × 104 nCi/g, at pH 7 and at an equilibrium radium concentration of 1000 pCi/L, were determined for a mixed culture, while the biomass of Penicillium chrysogenum adsorbed 5 × 104 nCi/g radium under the same conditions. The highest uptake value for a sample of F‐400 granular activated carbon was 3600 nCi/g at pH 7 and 1000 pCi/L radium concentration. The biosorptive radium uptake of microbial biomass is compared to literature values for other types of adsorbents. The most effective biomass types studied exhibited radium removals in excess of 99% of the radium in solution.
Growth monitoring and control through computer‐aided on‐line mass balancing in a fed‐batch penicillin fermentation
Authors: Mou Duen‐Gang , Cooney Charles L.
Published: December 2004

A computer‐aided methodology is developed for on‐line monitoring and control of cell growth in fed‐batch penicillin fermentation using a semidefined medium containing low corn steep liquor concentration (5.7 g/L). Cell growth is monitored and controlled with the use of experimental correlation and carbon‐balancing equatiions on a real‐time basis throughout the fermentation. Through a combination of feed‐forward and feedback control of sugar addition, residual glucose concentration in the broth was maintained below 1 g/L and cell‐growth rate was kept at constant at preset vaiues. The accuracy and reproducibility of this technique are demonstrated. The use of real‐time control of cell growth is expected to aid future investigations of this antibiotic fermentation.
Continuos IBE fermentation by immobilized growing Clostridium beijerinckii cells in a stirred‐tank fermentor
Authors: Krouwel P. G. , Groot W. J. , Kossen N. W. F.
Published: December 2004

The potential of continuous isopropanol–butanol–ethanol (IBE) fermentation by Ca–alginate‐immobilized Clostridium beijerinckii cells in a continuous stirred‐tank reactor is investigated. A mathematical model is presented to describe steady‐state reactor performance. It appeared to be possible to use the biocatalyst particles repeatedly for successive fermentations (at least three times for a total duration of two months). Reactor productivity was 6–16 times higher than that of a batch fermentation (free cells), while the solvents yield was also increased. Measurements of substrate, product, and biomass concentrations were only partially in agreement with the model; however, a solid basis for further technological developement of the process has been laid.
Permeabilities of composite membranes containing phospholipids
Authors: Sada Eizo , Katoh Shigeo , Terashima Masaaki
Published: December 2004

Two types of artificial membranes containing a phospholipid were prepared and their permeabilities were measured around the phase‐transition temperature of the phospholipid. The permeability of the membranes to a hydrophobic solute was higher than to a hydrophilic solute, and showed an abrupt change at the phase‐transition temperature of the phospholipid, similar to that in biomembranes and liposomes, caused by the fluidity change of the phospholipid at this temperature.
Production of Spirulina biomass: Maintenance of monoalgal culture outdoors
Authors: Vonshak A. , Boussiba S. , Abeliovich A. , Richmond A.
Published: December 2004

The effects of sodium bicarbonate concentration, population density, and temperature on the maintenance of an outdoor monoculture of the cyanobacterium Spirulina platensis were studied. A clear response by Spirulina to the concentration of bicarbonate was evident, with 0.2M bicarbonate representing the lowest concentration in which a monoculture could be maintained. When the temperatures fell during the winter period to some 20–25°C below the optimum for Spirulina, Chlorella sp. gradually increased and became the dominant species in the culture. Raising the temperature by covering the pond with transparent polyethylene resulted in a sharp decline in the population of Chlorella, and a gradual resumption of species dominance by Spirulina. In winter, there was an inverse relationship in the pond between the population density of Spirulina and the extent of contamination by Chlorella sp.; but no such effect was observed under field conditions at temperatures higher than 25°C.
Intensified controlled fish growth in tanks implementing a multipurpose flow device
Authors: Oron Gideon , Granoth Gila , Porath Dan
Published: December 2004

Fish biomass (Tilapia sp.) were raised at high stocking density in 1‐m3 tanks containing 450 L of water. The water was changed continously by means of a jet flow regulator. The jet flow regulator maintained adequate dissolved oxygen (DO) and a low ammonia level, while the suspended solids were discarded. In such a system, an annual yield of above 15 kg/m3 can be expected. The application of the jet flow regulator in aquaculture is discussed.
Pitfalls in the assay of carboxymethylcellulase activity
Authors: Lindner W. A. , Dennison C. , Quicke G. V.
Published: December 2004

A purified endocellulase from Sclerotium rolfsii and a crude cellulase preparation from Trichoderma reesei are used to illustrate several pitfalls associated with the assay of carboxymethylcellulase activity and the subsequent attainment of linear enzyme dilution curves. It is shown that the nature of both the enzymes and the substrate make the assay unsuitable for use in the calculation of enzyme recovery and purity.
Continuous simultaneous saccharification and fermentation of starch using Zymomonas mobilis
Authors: Lee J. H. , Pagan R. J. , Rogers P. L.
Published: December 2004

A continuous process involving simultaneous saccharification and fermentation of liquefied starch has been developed using Zymomonas mobilis. Amyloglucosidase retention and cell recycle have been effected by using an Amicon hollow‐fiber membrane system with a MW cutoff of 5000. Relatively high productivities of up to 60 g L−1 h−1 have been achieved at ethanol concentrations of 60–65 g/L. The system also offers the potential for reduced enzyme requirements for saccharification.
The performance of immobilized glucose isomerase supported by shrimp chitin in various types of reactors
Authors: Chen Fu‐Sen , Weng Hung‐Shan , Lai Ching‐Liang
Published: December 2004

Five different types of reactors were employed for glucose isomerization using shrimp shell as the support on which to immobilize the glucose isomerase. The Michaelis–Menten constants and effective diffusivity of glucose in the immobilized enzyme bed were experimentally determined and used in a theoretical analysis of the radial‐flow reactor. The fractional conversions of the radial‐flow, fluidizedbed, and packed‐bed reactors with the same ‐residence time were found experimentally to be almost the same. This result reveals that the use of radial‐flow and fluidized‐bed reactors for this immobilized enzyme system is highly feasible.
Production L‐tryptophan by Escherichia coli cells
Authors: Bang Won‐Gi , Lang Siegmund , Sahm Hermann , Wagner Fritz
Published: December 2004

Whole cells of Escherichia coli B 10 having high tryptophan synthetase activity were used directly as an enzyme source to produce L‐tryptophan from indole and L‐ or D,L‐serine. This strain is tryptophan auxotrophic, which is tryptophanase negative and, in addition, L‐ and D‐serine deaminase negative under production conditions. To avoid inhibition of tryptophan synthetase by a high concentration of indole, nonaqueous organic solvents, Amberlite XAD‐2 adsorbent, and nonionic detergents were used as reservoirs of indole in the reaction mixture for the production of L‐tryptophan. As a result, different effects were observed on the production of L‐tryptophan. Particularly, among the nonionic detergents, Triton X‐100 was very efficient. Using Triton X‐100 for production of L‐tryptophan from indole and L‐ or D,L‐serine by whole cells of Escherichia coli B 10, 14.14 g/100 mL and 14.2 g/100 mL of L‐tryptophan were produced at 37°C for 60 h.
Continuous production of L‐tryptophan from indole and L‐serine by immobilized Escherichia coli cells
Authors: Bang Won‐Gi , Behrendt Ulrich , Lang Siegmund , Wagner Fritz
Published: December 2004

Escherichia coli B 10, which has high activity of tryptophan synthetase, was grown in a 50‐L batch culture in order to determine in which growth phase the cells have the highest specific tryptophan productivity. Accordingly, whole cells of the stationary phase were used for immobilization in polyacrylamide beads. After immobilization, these immobilized cells had 56% activity of tryptophan synthetase compared with that of free cells. First, the properties of immobilized cells were investigated. Next, discontinuous productions of L‐tryptophan were carried out by using immobilized cells. In discontinuous production of L‐tryptophan by the batch, the activity remaining of immobilized cells was 76–79% after 30 times batchwise use. In continuous production of L‐tryptophan with a continuous stirred tank reactor (CSTR), the activity remaining of the immobilized cells was 80% after continuous use for 50 days. The maximum productivity of L‐tryptophan in this CSTR system was 0.12 g tryptophan L−1 h−1.
Effect of chemical modification of cellulose on the activity of a cellulase from Aspergillus niger
Authors: Boyer Rodney F. , Redmond Molly A.
Published: December 2004

Five chemically modified forms of cellulose were prepared, characterized, and tested as substrates for a homogeneous glucanohydrolase from A. niger. The relative order of reactivity at pH 4.0 was DEAE = PEI > benzyl DEAE > cellulose > P > CM.

The following abbreviations are used throughout the article: (RBB) Remazol brilliant blue R; (DEAE) diethylamino ethyl; (PEI) polethyleneimine; (CM) carboxymenthyl; (P) phospho; (DS) degree of RBB dye substitution of cellulose, in mol dye/100 glucose.

This indicates that positively charged cellulose substrates are more susceptible to hydrolysis by the cellulase. This observation strengthens an earlier proposal that caroxyl groups on the enzyme are involved in substrate binding and catalytic action. Chemical modification is suggested as a method to increase the rate of enzymatic hydrolysis of cellulose, a process now in the commercial development stage.
Some fluidization characteristics of biological beds
Authors: Hermanowicz S. W. , Ganczarczyk J. J.
Published: December 2004

The free‐fall terminal velocity of particles coated with a nitrifying biofilm was investigated. The drag force exerted by the liquid on a biocoated particle was found larger than that for an uncoated particle. A new formula for the drag coefficient was proposed. The wet density of biofilm was estimated as 1.14 g/cm3. A proposed modification of the Zaki‐Richardson method was successfully used for calculations of the porosity of a fluidized bed.
Production of biomas and β‐D‐galactosidase by Candida pseudotropicalis grown in continuous culture on whey
Authors: Gomez Amand , Castillo Francisco J.
Published: December 2004

The production of biomass and β‐D‐galactosidase by the lactose‐utilizing yeast Candida pseudotropicalis NCYC 744 in whey medium was studied. Apparent optimization of growth conditions and medium was done in continuous culture. Optimaql pH and temperature were 2.6 and 36–38°C, respectively, Limitations in Cu, Zn, and possbily Mn were detected in deproteinized whey medium. Additions of tryptophan estimulated growth of the yeast. Under optimal conditions in medium supplemented with excess tryptophan, Cu, Zn, and Mn the maximum values obtained: yeast concentration, 4.6 g/L; yeast productivity, 1.4 g/L h (at D = 0.35 h−1); enzyme volumetric productivity, 2100 U/L h (at D = 0.25 h−1); maintenance coefficient, 5–10 mg lactose/g cell h; saturation constant (Ks) for lactose, 4.76mM; maximum specific growth rate, (μmax), 0.47 h−1. No significant increase in specific enzyme activity (U/mg cell) was observed after medium optimiztion evidencing the importance of regulatory controls in enzyme synthesis.
Oxygen electrode dynamics: Three‐layer model—chemical reaction in the liquid film
Authors: Linek V. , Sinkule J. , Vacek V.
Published: December 2004

A general model of the transient behaviour of an oxygen probe is derived on more general assumptions than those previously considered. The present state of the art is shorly discussed in its relation to the newly derived equations: (1) the reducibility of the three‐layer diffusional model to two‐layer ones is discussed, and the two‐layer model considering the membrane and the liquid film is verified experimentally, (2) experimental and theoretical treatments of transient probe characteristics determination are examined, and (3) the influence of chemical reactions of the first order as well as of zero order (microorgaganism respiration) in measured media on transientd probe characteristics is quantified.
Dependence of biological treatment rate on species composition in activated sludge or biofilm. II: From models to theory
Authors: Vavilin V. A.
Published: December 2004

Traditional biological treatment models are “deduced” from formal chemical kinetics or dynamics of pure microorganism cultures growth. The best formal models give reasonable approximations of the biological treatment model with an ecosystem adaptation (ESA model). The model presented here explains some features of the biological treatment mechanism that cannot be described by formal models.
Mass transfer parameters in an immobilized glucoamylase column by pulse response analysis
Authors: Sirotti David A. , Emery Alden
Published: December 2004

Pulses of several nonreacting solutes were fed to a column containing immobilized enzyme catalyst beads. The response curves were recorded, and their first and second moments were determined by numerical integration. From the moment analysis, the void volume, internal porosity, and tortuosity of the support were calculated.
A Process for large‐scale isolation of β‐galactosidase from E. coli in an aqueous two‐phase system
Authors: Veide Andres , Smeds Anna‐Lisa , Enfors Sven‐Olof
Published: December 2004

A method suitable for large‐scale isolation of β‐galactosidase from a suspension of disintegrated E. coli cells has been developed. In an aqueous two‐phase system consiting of PEG 6000 and potassium phosphate, all cell debris and the major part of the proteins and nucleic acids were partitioned to the denser salt phase. Seventy‐five percent of the β‐galactosidase was recovered in the lighter PEG phase, giving a purification ratio of about 12.
Occurrence of glutamate dehydrogenase isoenzymes during growth of Oocystis alga
Authors: Lee B. H. , Picard G. A.
Published: December 2004

Oocystis sp., a unicellular green alga, contained two glutamate dehydrogenase isoenzymes: one was specific for NADH and the other for NADPH. Activity staining after gel electrophoresis indicated that one component in NADH‐GDH was not specific for the cofactor and three components in NADPH‐GDH. The optimal concentration of substrate, purification procedure and kinetic properties of both glutamate dehydrogenase (GDH) enzymes in vitro are presented. The kinetics of growth, nutrient removal and enzyme activities for Oocystis growing in wastewater showed that ammonia was preferentially utilized over nitrate and the medium was depleted before the maximum population was obtained in indoor culture. There was a sharp increase in NADPH‐GDH activity following the exhaustion of ammonia from the medium but NADH‐GDH activity remained unchanged. The NADPH‐GDH activity at the outset increased exponentially with time in greenhouse culture but then decreased sharply accompained by a rapid increase in biomass and nitrite concentration. The Km values for ammonia in this algal GDH was high, while glutamate synthase activity was not detected; this suggests that Oocystis may adapt to conditions of ammonia limitation by producing large quantities of NADPH‐GDH instead of using glutamate synthase pathway.
Modeling of experiments on biofilm penetration effects in a fluidized bed nitrification reactor
Authors: Denac M. , Uzman S. , Tanaka H. , Dunn I. J.
Published: December 2004

A four‐component, diffusion‐reaction model with double Michaelis‐Menten kinetics was used to describe the experimental data obtained from a laboratory biofilm, fluidized‐bed nitrification reactor. Theory and experiment demonstrated that the stoichiometric ratio (3.5 mg O2/mg NH‐N) can be employed as a criterion to determine whether the limiting substrate is oxygen or ammonia. For the present work, in the range of concentrations where limitation occurred, 4 mg/L NH‐N and 14 mg/L O2, the ratio of oxygen to ammonia in the bulk liquid determined which substrate was penetration‐limiting—O2 if <3.5 and NH if > 3.5. Halforder kinetics with respect to the limiting substrate described the apparent overall rates. Simulations provided biofilm concentration profiles which demonstrated the role of the oxygen‐ammonia ratio. Experiments indicated that, generally, high NO concentrations can be expected. These depend on the residence time, biofilm area, and oxygen concentration. This dependency was investigated with the model, as was the parametric sensitivity with respect to the saturation constants. Particularly important for the NO levels were the ratios of the saturation constants for oxygen.
Immobilization of glucoamylase and glucose oxidase in activated carbon: Effects of particle size and immobilization conditions on enzyme activity and effectiveness
Authors: Bailey James E. , Cho Y. K.
Published: December 2004

Glucoamylase and glucose oxidase have been immobilized on carbodiimide‐treated activated carbon particles of various sizes. Loading data indicate nonuniform distribution of immobilized enzyme within the porous support particles. Catalysts with different enzyme loading and overall activities have been prepared by varying enzyme concentration in the immobilizing solution. Analysis of these results by a new method based entirely upon experimentally observable catalyst properties indicates that intrinsic catalytic activity is reduced by immobilization of both enzymes. Immobilized glucoamylase intrinsic activity decreases with increasing enzyme loading, and similar behavior is suggested by immobilized glucose oxidase data analysis. The overall activity data interpretation method should prove useful in other immobilized enzyme characterization research, especially in situations where the intraparticle distribution of immobilized enzyme is nonuniform and unknown.
Least‐squares estimation of batch culture kinetic parameters
Authors: Ong S. L.
Published: December 2004

This article concerns the development of a simple and effective least‐squares procedure for estimating the kinetic parameters in Monod expressions from batch culture data. The basic approach employed in this work was to translate the problem of parameter estimation to a mathematical model containing a single decision variable. The resulting model was then solved by an efficient one‐dimensional search algorithm which can be adapted to any microcomputer or advanced programmable calculator. The procedure was tested on synthetic data (substrate concentrations) with different types and levels of error. The effect of endogeneous respiration on the estimated values of the kinetic parameters was also assessed. From the results of these analyses the least‐squares procedure developed was concluded to be very effective.
Rotating drum fermentor for plant cell suspension cultures
Authors: Tanaka Hideo , Nishijima Fuyuhiko , Suwa Mitsuru , Iwamoto Tetsuya
Published: December 2004

A rotating drum fermentor designed for plant cell suspension cultures was constructed and tested. The oxygen transfer coefficient (kLa) and power requirements in the fermentor were determined with the water system under various conditions and the relationship between them in the fermentor was clarified. Also, the relationship between kLa and the apparent viscosity in the fermentor was investigated in the cell suspension system. The rotating drum fermentor was found to be superior to the mechanically agitated fermentor in the capacity of oxygen supply under high viscosity and low hydrodynamic stress conditions. This finding was also confirmed by the experiments with plant cell suspension cultures.
Enzyme electrode for specific determination of L‐lysine
Authors: Romette J. L. , Yang J. S. , Kusakabe H. , Thomas D.
Published: December 2004

L‐Lysine α‐oxidase from Trichoderma viride Y244‐2 is immobilized in a gelatin support and fixed on a pO2 sensor. The enzyme electrode obtained is used in a continuous flow system in order to measure the concentration of L‐lysine in a fermentor. The sample oxygen‐content dependance of the signal is minimized because of the enzyme support properties. The enzyme electrode response is set for lysine concentration from 0.2mM to 4mM. The specificity of lysine is tested with other amino acids. The enzyme membrane for lysine electrode can be used 3000 times or stored six months with good stability.
Catalytic solvent delignification of agricultural residues: Organic catalysts
Authors: Ghose T. K. , Pannir Selvam P. V. , Ghosh P.
Published: December 2004

The effects of moderate‐temperature aqueous butanol pretreatment of rice straw on several organic catalysts have been studied. Maximum delignification was obtained with an aromatic organic acid catalyst. Presoaking of straw in aqueous improved delignification, particularly in high solid–liquid rations. However, due to the difficulty of penetration of lignin into the solvent phase, an increase in the solid‐liquid ratio appears to affect delignification. A two‐stage catalytic solvent process involving presoaking at 80°C followed by delignification at 120°C resulted in 83% removal of lignin in aqueous‐butanol, whereas 75% lignin removal was possible in ethanol. Higher reduction in the crystallinity was possible with etanol. Lignin produced by the solvent process offers desirable physical properties for polymer applications compared to Kraft lignin.
A kinetic model for the activated sludge process which considers diffusion and reaction in the microbial floc
Authors: Benefield Larry , Molz Fred
Published: December 2004

A mathematical model has been developed which describes substrate removal, oxygen utilization, and biomass production in an aggregated microbial suspension containing the substrate as a soluble biodegradable material and a uniform floc size. It is applicable to both steady‐state and transient conditions. The model, consisting of three partial differential equations and two ordinary differential equations, takes into account the flow pattern in the reactor, intraparticle mass transport of oxygen and substrate, and biochemical reaction by individual cells embedded in the floc. Efficient numerical solution of the coupled nonlinear equations is obtained using an implicit finite difference approach for both the reactor and floc equations. A convergent solution is realized through block interation utilizing the tridiagonal algorithm. Results indicate that a unifying theory of activated sludge dynamics will have to consider coupling between floc chemical kinetics and changes in the bulk liquid characteristics. Floc size emerges as an important influence on system performance. It appears necessary to distinguish between a system response caused by diffuslonal resistances and nutrient limitations within the floc and a response caused by physiological adaption when analyzing the transient behavior of an activated sludge process. Future research should be devoted to rigorous laboratory determinations of model parameters along with extensions to include limitations of nutrients other than orgabnic carbon and oxygen.
Effect of gamma‐ray irradiation on alcohol production from corn
Authors: Han Y. W. , Cho Y. K. , Ciegler A.
Published: December 2004

Cracked corn was irradiated with gamma rays at 0–100 Mrad and the effects of the irradiation on sugar yield, susceptibility to enzymatic hydrolysis of starch, yeast growth, and alcohol production were studied. Gamma irradiation at 50 Mrad or greater produced a considerable amount of reducing sugar but little glucose. At lower dosages, gamma irradiation significantly increased the susceptibility of corn starch to enzymatic hydrolysis, but dosages of 50 Mrad or greater decomposed the starch molecules as indicated by the reduction in iodine uptake. About 12.5% reducing sugar was produced by amylase treatment of uncooked, irradiated corn. This amount exceeded the level of sugar produced from cooked (gelatinized) corn by the same enzyme treatment. The yeast numbers in submerged cultivation were lower on a corn substrate that was irradiated at 50 Mrad or greater compared to that on an unirradiated control. About the same level of alcohol was produced on uncooked, irradiated (105−106 rad) corn as from cooked (121°C for 30 min) corn. Therefore, the conventional cooking process for gelatinization of starch prior to its saccharification can be eliminated by irradiation. Irradiation also eliminated the necessity of sterilization of the medium and reduced the viscosity of high levels of substrate in the fermentation broth.
Theory and applications of unstructured growth models: Kinetic and energetic aspects
Authors: Esener A. A. , Roels J. A. , Kossen N. W. F.
Published: December 2004

Microbial kinetics and energetics are discussed in connection with the formulation of unstructured growth models. The development of microbial energetics and the use of macroscopic methods in the study of microbial growth are briefly evaluated. The general approach to the modelling of microbial growth has been critically discussed and a strategy for the formulation of unstructured models is presented. A simple unstructured model based on Monod kinetics and the linear relation for substrate consumption is evaluated with reference to extensive experimental and simulation data obtained in batch, fed‐batch, and continuous cultivation modes. Choice for a kinetic expression is discussed and has been shown not to be critical in most situations. It is shown that during growth in batch mode, the behavior of the system is rigidly fixed by the kinetic parameter: the maximum specific growth rate. The energetic parameters have minimal influence. In continuous cultivation the behavior is fixed by the energetic parameters: the maximum yield and the coefficient of maintenance. Implications of these observations have also been discussed. The linear relation for substrate consumption is tested with continuous culture data. It is shown that significant deviations at low growth rates cannot be fully accounted by the loss of viability. The situations where unstructured models will be adequate or not for system description, are evaluated and checked experimentally. Influence of an environmental factor, the temperature, on the unstructured model parameters is also quantitatively described. It is concluded that the art of unstructured model building has already reached its maturity and that now much effort should be channelled into the development and verification of structured models.
Effect of glucose and other sugars on the β‐1,4‐glucosidase activity of Thermomonospora fusca
Authors: Ferchak John D. , Pye E. Kendall
Published: December 2004

The cell‐associated β‐glucosidase activity of Thermomonospora fusca, strain YX, showed both PNPGase and cellobiase activities. The cellobiase activity was found by HPLC assay to have very low product inhibition, whereas the PNPGase activity was more significantly inhibited. Of the various sugars and sugar analogs tested for inhibition of the PNPGase activity, gluconolactone had the greatest effect. The low product inhibition of the cellobiase activity was further demonstrated by the production of glucose syrups to 20% concentration from both cellobiose and swollen cellulose (Avicel). This characteristic is of practical importance in the development of a commercial process for the production of glucose syrups from cellulose. Growth experiments gave further evidence for the probability of separate enzymes for the PNPGase and cellobiase activities.
Reaction characteristics of an immobilized yeast producing ethanol
Authors: Furusaki Shintaro , Seki Minoru , Fukumura Kenichi
Published: December 2004

The reaction behavior of Saccharomyces formaosensis imobilized by polyacrylamide gel is presented. Two types of the immobilized yeast are studied, i. e. the immobilized resting yeast and the immobilized growing yeast. For both of the yeast, reaction retes are expressed by the Michaelis‐Menten type equation with a linear ethanol inhibition factor. The Michaelis constants aere close each other, but considerably larger that of native S. cerevisiae. Distribution of the growing yeast cell inside the carrier gel is presented. It is found that the cell density is somewhat higher near the surface of the carrier.
Preparation of immobilized α‐amylase covalently attached to granular polyacrylonitrile
Authors: Handa Takashi , Hirose Akira , Akino Toshiro , Watanabe Kosuke , Tsuchiya Haruo
Published: December 2004

In this report, α‐Amylase originating from Bacillus subtilis (liquefying type) was immobilized on partially imidoesterized polyacrylonitrile (PAN) by covalent bonding. For the preparation of immobilized α‐amylase, which has a high activity and high stability to repeated use, the optimum conditions for the preparation reaction were investigated. The optimum conditions for the preparation reaction were quantified on the basis of the enzymatic activity, the preservation of the activity during repeated use in batch process and the protein content on the support. Further‐more, enzymatic properties of immobilized α‐amylase prepared at optimum conditions were compared with the native enzyme. The optimum temperature and reaction time for the imidoes‐terification reaction were 30°c and 6 h, respectively, whereas those of the amidinatin reaction were 30–40°C and more than 3 h, respectively; the optimum pH range was 9–10. Immobilized α‐amylase prepared at the optimum conditions was very stable against the repeated use and had more than 90% of relative to activity of the first use after the tenth procedure. The initial reaction rate of immobilized α‐amylase was lower than native α‐amylase, but same amount of reducing sugars were produced after the reaction passed for more than 90 min. The immobilized α‐amylase was less stabel at the high temperature and the more basic media. However, after long incubation time, immobilized α‐amylase was more stable than the native enzyme in exposure to heat and a storng base.
The continuously fed batch reactor for measuring microbial growth rates
Authors: Webster Ian A.
Published: December 2004

The contiuously fed batch reactor (CFBR) is proposed as an alternative technique to the traditional chemostat and batch cultures, for measuring microbial growth rates. After reviewing the pitfalls which plague the conventional growth measurement techniques, the methodology for operating the CFBR to generate specific growth‐rate‐versus‐substrate‐concentration data is detailed. This information is extracted from the transient state of the CFBR where both the biomass and substrate concentration show extrema in time. It is suggested that the CFBR can be used for measuring microbial growth rates at low rates at low substrate concentrations where the chemostat method normally encounters difficulties.