bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of the release of undegraded material extracted from cells by ultrasound
Authors: Coakley W. T. , Brown R. C. , James C. J. , Gould R. K.
Published: December 2004

The time course of release of intact labile material from cells by cavitating ultrasound is examined. Curves are presented which show the yield of intact subcellular components obtainable from cells as a function of sonication time for various values of the ratio of inactivation rate to release rate. The general cases where inactivation of released product is concentration dependent (chemical) and concentration independent (mechanical) are considered.

For a flow system the time of attainment of equilibrium concentration of active product is analyzed as a function of flow rate, release rate, inactivation rate, and volume of chamber. Curves of optimal yields to be expected for batch and flow systems are presented. It is shown that sonochemical inactivation can be made negligible by sonication of high cell concentration suspensions.
Thermodynamics and rheology of the Hughes press
Authors: Scully D. B. , Wimpenny J. W. T.
Published: December 2004

Among the methods used for the rupture of cells by means of solid shear, the Hughes press is best known. It operates by forcing an aqueous suspension of cells previously frozen at −27°C under pressure through a narrow circumferential gap. The mode of action requires a knowledge of the isentropic compression of the solid phase and its possible involvement with a phase change from ice I to ice III. It is shown that the mechanical properties of the solid mixture are relevant. A model is proposed of the plastic flow for the geometry of the press and it is shown that cell breakage is proportional to the velocity of the plunger and inversely proportional to gap width.
Experimental studies on a kinetic model for design and operation of activated sludge processes
Authors: Gaudy A. F. , Srinivasaraghaven R.
Published: December 2004

Previous experimentation in our laboratory has shown that the classical theory developed for continuous growth of pure cultures in completely mixed aerobic systems in which the recycle cell concentration factor, c (where c = XR/X), is a selectable system constant, did not provide a suitable model for the heterogeneous (natural) populations of the activated sludge process. Another model was derived in which the recycle cell concentration, XR was employed as a system constant instead of c, and computational analysis was performed. Laboratory pilot plant experimentation was undertaken in order to determine whether a “steady state” in aerator biological solids concentration, X̄, and substrate concentration, S̄, could be approached under this mode of operation. Studies were performed at various organic feed concentrations holding dilution rate, D, at 0.125 hr−1, hydraulic recycle ratio, α, at 0.25, and XR at 10,000 mg/liter. Also, values of maximum specific growth rate, μmax, and saturation constant, Ks were determined. It was found that the model approached the steady state condition with heterogeneous populations more closely than did the classical model, and the high degree of treatment efficiency predicted by the model was demonstrated experimentally.
Mixing in anaerobic digestion
Authors: Verhoff F. H. , Tenney M. W. , Echelberger W. F.
Published: December 2004

The mixing of the anaerobic digester contents significantly influences the efficiency of this operation; in particular, hydraulic dead zones are extremely detrimental to the reaction kinetics involved in anaerobic digestion. An analysis of the relative importance of thermal fluid movement in the digester to those caused by fluid inflow and outflow is presented. As an example, these principles are applied to a digester at the South Bend Wastewater Treatment Plant. Experimental measurements, which have general applicability for the measurement of digester mixing volume, confirm the theoretical conjectures. Various types of optimizations can be attempted on this mixing operation. One such optimization applied to gas lift mixers, as employed in the South Bend Treatment Plant, is illustrated.
Degradation of lignin by combined chemical and biological treatment
Authors: Stern Arthur M. , Gasner Larry L.
Published: December 2004

It has been demonstrated that ozone dosages of 0.06 lb and 0.78 lb per pound of lignin can reduce the optical density (in the visible range) of the latter by 82% and 92%, respectively. The reduction in color is accompanied by a shift in the molecular weight distribution of lignin from a broad peak of between 20,000 and 70,000 to lower molecular weight, species including substantial amounts possessing a molecular weight of 1000 or less. The cost of decolorizing a typical kraft paper bleach effluent is estimated to be under 50¢/1000 gal which compares favorably with competitive decolorizing processes. Lignin ozonation results in the production of a series of decolorized products which can serve as the sole source of carbon for a variety of microorganisms. Feasibility studies indicated that at least 40% of the ozonated material can be transferred into microbial biomass (protein) as well as other products of commercial interest such as fumaric acid and penicillin.
Cost optimization of activated sludge systems
Authors: Middleton Andrew C. , Lawrence Alonzo W.
Published: December 2004

Activated sludge is a widely used aerobic biological waste‐water treatment process. A rational approach to least cost design of an integrated system is described which includes the following processes: activated sludge reactor, final settling tanks, gravity thickening, and aerobic sludge digestion. Both capital and operation and maintenance costs are considered. Biological reactor design is based on microbial kinetic concepts and continuous culture of microorganisms theory. Biological solids retention time (θc) is utilized as the primary independent design variable to which system performance is related, e.g., effluent quality, ammonia oxidation, and excess sludge production. Liquid‐biomass separation is based on the batch flux technique, a rational approach to design of gravity separators (final settling tanks). Trade‐offs among reactor volume, clarifier size, recycle pumping capacity, thickener capacity, digester volume, air requirements, and sludge production are discussed. The optimum design is taken as the combination of these parameters within the acceptable design domain, determined by effluent quality criteria, that results in minimum cost. While the method described is general, design of a given treatment system depends on availability, from lab or pilot studies, of system specific numerical values for biological growth coefficients and biomass setting characteristics. A design example illustrates the approach.
The extended Kalman filter applied to a continuous culture model
Authors: Svrcek W. Y. , Elliott R. F. , Zajic J. E.
Published: December 2004

The temperature‐dependent endogenous metabolism model of single species continuous culture dynamics is utilized in the computer simulation of the Kalman filter state estimation technique. Parameters of the nonlinear equations can be “tracked” while variance in measured states can be damped. The state estimator is illustrated in, the context of conventional control strategies.
Large‐scale purification of Qβ‐virus by differential centrifugation
Authors: McGregor W. C. , Round J. J. , Ramel A. H.
Published: December 2004

Bacterial RNA virus, Qβ, has been purified in gram amounts by differential centrifugation. Final separation of the virus from host E. coli rRNA was based on the density differential in the pellet. The method provided a simplified alternative to the more conventional rate zonal or isopycnic zonal centrifugation techniques.
Growth of Spirulina maxima algae in effluents from secondary waste‐water treatment plants
Authors: Kosaric N. , Nguyen H. T. , Bergougnou M. A.
Published: December 2004

Spirulina maxima, a high protein alga, was grown in effluents from the London municipal waste treatment plant. Optimum growth conditions were developed, the composition of algae and the removal of nitrogen and phosphorus in effluents were studied. The advantages of this process in tertiary waste‐water treatment and the quality of the single cell protein were investigated.
Affinity chromatography purification of diphtheria toxin
Authors: Cukor George , Readio Josephine D. , Kuchler Robert J.
Published: December 2004

NAD was covalently linked to Sepharose‐4B using a 6 carbon spacer. Sterile, dialyzed spent culture medium containing 100 Lf/ml of diphtheria toxin or material concentrated by (NH4)2SO4 precipitation containing 1500 Lf/ml, was chromatographed on a column of NAD–Sepharose. Ultraviolet absorbing material which did not flocculate with diphtheria antitoxin was eluted with 0.02M phosphate buffer. When the elation buffer was changed to one containing 0.5M NaCl, purified toxin was eluted off the column.
Production of Sindbis, influenza, and vesicular stomatitis viruses in chicken embryo and rat embryo cell suspensions
Authors: Keay L. , Schlesinger S.
Published: December 2004

Studies were carried out on the production of Sindbis, influenza and vesicular stomatitis viruses in suspensions of chicken embryo and rat embryo cells. The yield of Sindbis virus in chicken embryo cell suspensions was independent of the multiplicity of infection over the range 0.0001 to 0.01 although reduction in multiplicity caused a delay in virus production. With influenza virus the use of higher multiplicities gave increased virus yields possibly due to the very slow production at low multiplicities. In both monolayer and suspension cultures of chicken embryo cells addition of serum or use of media richer than minimum essential medium (Eagle) had little effect on Sindbis virus production, but if the glucose were omitted the virus yield was markedly reduced. In cell suspensions, a marked reduction in virus yield occurred if infection were delayed more than 24 hr after cell preparation whereas in monolayers the delay of infection allowed cell propagation and hence a higher yield of virus. It was also shown that vesicular stomatitis virus can be produced in chicken embryo cell suspensions, and that rat embryo primary cell suspensions can be used to prepare both Sindbis and vesicular stomatitis viruses. Sindbis virus obtained from chicken embryo cell suspensions was purified by polyethylene glycol precipitation and sucrose density gradient centrifugation and shown to contain only those proteins previously identified as viral, without any contamination from chicken cell proteins. The relative ease and economics of virus production by cell suspension and monolayer methods is compared.
A mild method of general use for covalent coupling of enzymes to chemically activated collagen films
Authors: Coulet Pierre R. , Julliard Jacques H. , Gautheron Danièle C.
Published: December 2004

Films of highly polymerized collagen, prepared in industrial conditions, were chosen for surface covalent binding of enzymes because of their insolubility, mechanical resistance, proteic nature, hydrophilic properties and for their abundance in chemically activable COOH. Untanned films, previously acid‐ methylated, were activated by acyl azide formation. After removal of reagents by repeated washing, the coupling of enzyme was performed by immersion of the activated film in the enzyme solutions (2 to 3 hr, 0°C). The procedure is particularly mild since the enzymes never come into contact with chemical reagents, and thus avoid all denaturing processes. All the enzymes tested were successfully bound: glutamate dehydrogenase, lactate dehydrogenase, malate dehydrogenase, aspartate aminotransferase, glutamate pyruvate transaminase, creatine kinase, hexokinase, trypsin, and urease. As tested with aspartate amino transferase, enzymatic activity remained constant for months (100% after 5 months) in spite of repeated use of the film at 30°C, washing and storage in buffer at 4°C between assays.
Influence of intraparticle diffuisional limitation on the observed kinetics of immobilized enzymes and on catalyst design
Authors: Regan D. L. , Lilly M. D. , Dunnill P.
Published: December 2004

Numerical solutions to the equations describing simultaneous mass transfer and enzymic reaction within porous spherical particles have been used to examine the effect of enzyme content and other parameters on the kinetic behavior of immobilized enzymes. These solutions have also been compared with experimental data for enzymes immobilized to DEAE‐cellulose particles. The influence of particle size and enzyme content on catalyst design is discussed.
Immobilized tannase
Authors: Weetall H. H. , Detar C. C.
Published: December 2004

The enzyme tannase has been immobilized on an inorganic support by covalent attachment. This immobilized enzyme was characterized and half‐lives determined. Since this enzyme has application in the treatment of tea cream, experiments were also carried out to determine the effect of tea on enzyme half‐life.
Enzymatic RNA reduction in disintegrated cells of Saccharomyces cerevisiae
Authors: Lindblom Marianne , Mogren Håkan
Published: December 2004

Degradation of UNA by endogenous RNase in cell suspensions of Saccharomyces cerevisiae was found to be achieved by mechanical disintegration followed by incubation in the presence of NaCl. The incubation parameters pH, temperature, time, and concentration of NaCl were investigated. Protein concentrates with a low content of RNA were obtained by precipitation of the incubated suspensions and separation of the degradation products.

On a pilot plant scale the incubation was performed at 50°C and pH 5.6 in the presence of 3% NaCl for 20 min. Kilogram quantities of protein concentrates containing 1.4% RNA and 8.2% nitrogen were obtained. The RNA reduction and the nitrogen yield was 85 and 60%, respectively. The yield of amino acids was about 75%. The process described can probably be applied for large‐scale production.
Stability of commensalistic systems
Authors: Reilly Peter J.
Published: December 2004

The response of two‐species commensalistic systems in a chemostat has been investigated after perturbations in steady state conditions and after step changes in dilution rate. The system is inherently stable with not more than three overshoots and undershoots possible. More complicated commensalistic systems are less stable, with limit cycle response occurring after dilution rate changes when feedback inhibition and feedforward activation occurs. In general variation of feedback parameters is more effective in changing the behavior of the systems than variation of feedforward parameters. Limited agreement with the experimental data of Chao and Reilly was obtained.
Optimization in the recovery of a labile intracellular enzyme
Authors: Augenstein D. C. , Thrasher K. , Sinskey A. J. , Wang D. I. C.
Published: December 2004

A high molecular weight intracellular enzyme of Bacillus brevis ATCC 9999 is released when the organism is disrupted by sonication of homogenization. However, both processes also degrade the enzyme. Assays for protein release and specific enzymatic activity of the released protein indicate that both release and degradation can be represented by first‐order kinetic models. Utilization of the difference between the kinetics of release and degradation allows optimization in the recovery of this enzyme for both the sonication and homogenization processes.
Preparation of immobilized enzymes by N‐Vinylpyrrolidone and the general properties of the glucoamylase gel
Authors: Maeda H. , Suzuki H. , Yamauchi A. , Sakimae A.
Published: December 2004

Immobilized glucoamylase, invertase, and β‐galactosidase were prepared by using N‐vinylpyrrolidone monomer (VP) under γ‐ray irradiation. The enzyme‐VP solutions were gelled by irradiation with 2.9 Mrad and the added enzymes were almost completely entrapped. Activity losses on entrapping were 55% for the VP‐glucoamylase gel, and more than 90% in the case of VP‐invertase and VP‐β‐galactosidase gels. No leakage of enzyme from these gels could be detected within 1 hr. The VP‐glucoamylase gel was capable of hydrolyzing dextrin (mol wt 10,400) to glucose and the glucose equivalent was equal to that obtain able with native enzyme. The optimum temperature, heat stability, pH activity curve, and pH stability of VP‐glucoamylase gel were slightly inferior to those of native enzyme, while Km was a little larger than that of native enzyme.
Continuous production of L‐citrulline by immobilized Pseudomonas putida cells
Authors: Yamamoto Kozo , Sato Tadashi , Tosa Tetsuya , Chibata Ichiro
Published: December 2004

The microbial cells of Pseudomonas putida ATCC 4359 were immobilized by entrapment in a polyacrylamide gel lattice. Enzymatic properties of L‐arginine deiminase of the immobilized P. putida cells were investigated and compared with those of the intact cells. The permeability of substrate or product through the cell wall und the heat stability of the enzyme were increased by immobilization of the cells. No difference was observed between pH activity curves of the intact and immobilized cells. The optimal temperature for the formation of L‐citrulline was 37°C for the intact cells and 55° C for the immobilized cells.

When an aqueous solution of 0.5M L‐arginine hydrochloride (pH 6.0) was passed through a column packed with the immobilized cells at a flow rate of SV = 0.26 at 37°C, L‐arginine was completely converted to L‐citrulline. The enzyme activity of the column was stable and the continuous production of L‐citrulline could be carried out at 37°C for the month by using the immobilized cell column. From the effluent of the column, L‐citrulline was easily obtained in a good yield.
Continuous production of urocanic acid by immobilized Achromobacter liquidum cells
Authors: Yamamoto Kozo , Sato Tadashi , Tosa Tetsuya , Chibata Ichiro
Published: December 2004

Several microorganisms having higher L‐histidine ammonia‐lyase activity were immobilized into polyacrylamide gel lattice. The yield of enzyme activity by immobilization was highest in Achromobacter liquidum IAM 1667. As A. liquidum has urocanase activity, the cells were heat‐treated at 70°C for 30 min to inactivate the urocanase.

Enzymatic properties of the immobilized A. liquidum cells were investigated and compared with those of the intact cells. No difference was observed between the pH activity curve and optimal temperature for the intact and immobilized cells. The permeability of substrate or product through the cell wall was increased by immobilization of the cells.

When an aqueous solution of 0.25M L‐histidine (pH 9.0) containing 1mM Mg2+ was passed through a column packed with the immobilized A. liquidum cells at a flow rate of SV = 0.06 at 37°C, L‐histidine was completely converted to urocanic acid. The L‐histidine ammonia‐lyase activity of the immobilized cell column was stable over 40 days at 37°C. From the effluent of the immobilized cell column, Urocanic acid was easily obtained in a good yield.
Performance characteristics of continuous yeast‐alcohol fermentors with no mechanical stirring
Authors: Wick Emil , Popper Karel , Graham Robert P.
Published: December 2004

Continuous fermentation of grape juice was studied in three basic kinds of nonmechanically stirred fermentors, classified according to the direction in which flow is applied against settling: upward‐flow, slant‐flow, and horizontal‐flow.

Fermentation kinetics were found to be zero‐order, thus rate was directly proportional to cell density.

Completeness of fermentation depends upon yeast characteristics (growth rate flocculation), fermentor geometry (settling depth, flow path length), and upon flow velocity.

Fermentor analysis demonstrated that to achieve complete fermentation in the minimum juice holding time, efficient cell retention as well as rapid yeast growth and fermentation rates are required. Fermentor design and operation are discussed in the light of this analysis.
Automated instrument for measuring biological transport kinetics over intervals of a few seconds
Authors: Brown Olen R. , Barton Jerry
Published: December 2004

Automated sampling device was designed to permit determination of rates of biological transport of metabolites into cells. The substrate was automatically introduced into a stirred cell suspension at 37°C. The first sample was automatically taken after a mixing interval of 1 sec and nine subsequent samples were taken at programmable intervals (1 to 100 sec). The samples were forced by pressure differential (vacuum) through 0.4 μ pore size membranes and approximately 50 μl were collected in disposable cups. The duration of the sampling interval was controllable down to 0.1 sec. The samples preserved records of the substrate concentrations in solution at the time of filtration. With the use of suitable radioactive labeled isotopes, the changes in substrate concentrations may be conveniently measured by liquid scintillation spectrometry, but other analytical procedures of suitable sensitivity may be used. Initial and steady‐state transport rates of succinate and glucose in Escherichia coli were obtained using the device.
Deactivation of immobilized beef liver catalase by hydrogen peroxide
Authors: Altomare Robert E. , Kohler Joseph , Greenfield Paul F. , Kittrell James R.
Published: December 2004

Immobilized beef liver catalase has been used in a flow reactor to decompose hydrogen peroxide; at the same time the catalase is inactivated by its substrate. A model has been developed which predicts this rate of decomposition of peroxide and inactivation of catalase. First order dependence on peroxide concentration is assumed. The model was verified by experiment for a range of operating conditions and then used to predict the effects of a change in operating variables.
Response of biological reactors to sinusoidal variations of substrate concentration
Authors: Sundstrom D. W. , Klei H. E. , Brookman G. T.
Published: December 2004

A well‐mixed biological reactor with continuous addition of biological solids was subjected to sinusoidal variations in inlet substrate concentration. The phase lag between inlet and outlet concentrations increased with increasing frequency. The deviation of measured substrate concentrations from initial steady‐state concentrations was observed to have a maximum near a frequency of 1 cycle per residence time. Measured concentrations of substrate and biomass in the reactor differed significantly from concentrations predicted by the Monod kinetic model.
Influence of oxygen and substrate concentrations on the ideal film thickness and the maximum overall substrate uptake rate in microbial film fermenters
Authors: Howell J. A. , Atkinson B.
Published: December 2004

The criterion for the oxygen limitation of substrate uptake in microbial film fermenters is expressed in terms of diffusion coefficients, utilization coefficients, and the free solution concentrations of substrate and oxygen. It is proposed that the ideal film thickness in such fermenters is equal to the penetration depth of the limiting substrate. The ideal film thickness is calculated, in terms of the parameters contained in the criterion for oxygen limitation, for three separate kinetic rate expressions. It is found that for the air–glucose–microbe system a simplified kinetic rate expression can be used and the region of dependence on two substrates is shown to be very limited. This is not true for other systems. Maximum uptake rates are calculated for a range of concentrations. Finally, it is shown that the procedure used can be generalized to determine the limiting substrate in a multisubstrate system and to calculate ideal film thickness and uptake rates for any pair of substrates where the kinetics of substrate uptake are known for the individual microorganism.
Kinetic studies of α‐galactosidase‐containing mold pellets on PNPG hydrolysis
Authors: Kobayashi Harumi , Suzuki Hideo
Published: December 2004

Little is known about techniques for applying untreated microbial cells containing enzymes directly to industrial processes as a biocatalyst. The kinetic behavior of α‐galactosidase‐containing spherical pellets which are formed naturally under given conditions in a submerged culture of Mortierella vinacea was studied on the hydrolysis of PNPG (p‐nitrophenyl–α–D‐galactopyranoside). The effect of intraparticle diffusion on the overall reaction rate was assessed by the use of an effectiveness factor, which was calculated by the approximate solution to the equation derived from the mass balance within a pellet. The experimental effectiveness factors were found to be represented as a single function of the modified Thiele modulus, including such parameters as pellet size, enzyme concentration in the pellet, and substrate concentration. As the diffusional effect became more significant, the marked substrate inhibition as seen for a five enzyme disappeared gradually. The effect of product inhibition on the pellets was much weaker than that for a free enzyme at a given substrate concentration. In the region of diffusion controlled reaction, it was found that the rate is proportional to the square root of the enzyme concentration in the pellet. In addition, similarly to what was reported previously for a free enzyme, the reaction in a batch system was found to be approximately representable as simple first‐order kinetics in which the rate constant was dependent on the initial substrate concentration.
Combined external and internal mass transfer effects in heterogeneous (enzyme) catalysis
Authors: Frouws M. J. , Vellenga K. , De Wilt H. G. J.
Published: December 2004

A graphical method is outlined in order to calculate the conversion under combined intra‐ and extraparticle transport limitations using the existing effectiveness factor charts for intraparticle diffusion.

This method is applied to the case of an immobilized enzyme, assuming that the kinetics are of the Michaelis‐Menten type.
Temperature dependence of a diffusion‐limited immobilized enzyme reaction
Authors: Buchholz K. , Rüth W.
Published: December 2004

The apparent activation energy of N‐α‐benzoyl‐L‐arginine‐ethyl ester (BAEE) hydrolysis by immobilized trypsin varies with the bulk substrate concentration from its maximum value, comparable to that of the free enzyme, to considerably lower values. Thus, with a concentration change from 3 × 10−2 to 10−4 M the apparent activation energy diminishes from 9.5 to 4.5 kcal/mol. This experimental finding is interpreted to be due to Michaelis‐type kinetics in a heterogeneous system, in one case reflecting the temperature dependence of the maximal enzyme reaction rate, in another case illustrating the diffusion limited overall reaction at low substrate concentrations. As a consequence it may not be feasible to operate a reaction at elevated temperatures in a high conversion range, since diffusion limitation may restrict the enhancement of the overall reaction rate. Some further data are given concerning the buffer effect on the reaction rate, which should occur due to its limitation by proton transfer in the buffer‐free system.
Conversion of L‐sorbose to L‐sorbosone by immobilized cells of Gluconobacter melanogenus IFO 3293
Authors: Martin C. K. A. , Perlman D.
Published: December 2004

Gluconobacter melanogenus IFO 3293 cells capable of converting L‐sorbose to L‐sorbosone were immobilized in polyacrylamide gel. The preferred polymer composition for high activity and stability was determined to contain a total monomer concentration of 7.2% and 16.6% crosslinking agent. No significant differences in optimal conditions for conversion, e. g., pH and temperature, were found in comparison with free cell suspensions. However, in the absence of L‐sorbose, the thermal stability of immobilized cells was lower. After the initial loss, the conversion activity of immobilized cells increased, possibly due to lysis, and this increase was related to the polymerization conditions and the incubation temperature for the L‐sorbose conversion.

The enzymatic activity and stability of the immobilized cells also depended on the physical form of the gel and the aeration levels. Addition of electron acceptors or addition of L‐sorbosone to the medium reduced, while addition of neomycin, ampicillin, chloramphenicol, and tetracycline increased the stability of the enzymatic activity.
Protozoan feeding and bacterial wall growth
Authors: Bonomi Antonio , Fredrickson A. G.
Published: December 2004

Monod's model is often assumed to describe the kinetics of feeding of a protozoan population on a bacterial population in a chemostat. An earlier study (J. L. Jost et al., J. Bacteriol, 113, 84 (1973)) of the feeding of Tetrahymena pyriformis on either Escherichia coli or Azotobacter vinelandii found that this model correctly predicted the occurrence of sustained oscillations of population densities but made predictions of minimum bacterial population densities that were much smaller than those observed. The earlier study removed the discrepancy between the model and data by replacing Monod's model with a different model. It is shown in the present study that the discrepancy can be explained equally as well if Monod's model for the feeding relation is retained and if, in addition, growth of bacteria on the chemostat walls is allowed for in the model equations.
Pilot plant production of glucose with glucoamylase immobilized to porous silica
Authors: Lee Douglas D. , Lee Yoon Y. , Reilly Peter J. , Collins Edgar V. , Tsao George T.
Published: December 2004

Glucoamylase was immobilized to porous silica and its kinetics and stability were observed with acid‐ and α‐amylase‐hydrolyzed dextrin as feed. The enzyme was found to be extremely stable in both laboratory and pilot plant operations. When the feed had been previously only lightly hydrolyzed, pore diffusion limitation caused appreciable decreases in glucose production rate. The severity of starch hydrolysis to dextrin markedly affected ultimate glucose yields. The diffusional gradients present in the carrier pores caused the immobilized enzyme to yield lower glucose concentrations than the free enzyme at similar feed conditions.
Daughter cells as an important factor in determining the physiological state of yeast populations
Authors: Vraná Dagmar
Published: December 2004

Cells of Candida utilis grown in a single‐stage chemostat at D = 0.05, 0.1, 0.25, and 0.35 hr−l were separated into a fraction of scar‐bearing mother cells and a fraction of scar‐free daughter cells. The scar‐free cells were transferred into small batch cultures where the length of the maturation phase, changes in length and width of cells, specific growth rate, and specific rate of RNA and protein synthesis were examined for 5 hr. The daughter cells grown at D = 0.05 hr−1 were very small at the moment of separation from the mother cells (about one‐third of the mother cell). Their maturation phase (in a batch culture), at the beginning of which they attain the specific growth rate approaching the μmax of the strain used, lasts for 3 hr. On the other hand, daughter cells grown at D = 0.35 hr−1 are almost the same size as the mother cells at the moment of separation. After transfer to a batch culture they begin to bud almost immediately. Similarly, in their other morphological and physiological parameters they differ strikingly from immature daughter cells which are formed at low specific growth rates. The importance of these differences from the point of view of mathematical modeling of growth processes is discussed.
A heat transfer study on packed bed reactors of immobilized glucoamylase
Authors: Marsh David R. , Tsao George T.
Published: December 2004

Enzymes are generally sensitive to temperature changes. Porous glass particles used for glucoamylase immobilization are poor thermal conductors and a non‐uniform temperature distribution can conceivably develop in a packed bed reactor of immobilized glucoamylase on porous beads. This study was made to determine experimentally the temperature and concentration profiles in an immobilized glucoamylase column. This work provides a procedure for examining possible heat effects on reactor column performance in enzyme applications.
Inhibition‐threshold substrate concentrations
Authors: Wayman M. , Tseng M. C.
Published: December 2004

A proposed substrate inhibition model (M. C. Tseng and M. Wayman, Can. J. Microbiol., 21, 994 (1975)),

derived from yeast growth rates has been applied to data for bacterial growth: Pseudomonas methanica grown on methanol and Arthrobacter AK19 grown on n‐butanol. The model represents the experimental data very well.
The effect of aeration intensity on the biochemical composition of Baker's yeast: Activities of enzymes of the glycolytic and pentose phosphate pathways
Authors: Oura Erkki
Published: December 2004

A series of baker's yeast continuous cultivations were made using different intensities of aeration. The experimental conditions were such as to eliminate the effects caused by high glucose concentrations in the medium on the formation of enzymes. The variation in activity of several enzymes was investigated and distinct changes were noted. The activities of hexokinase and alcohol dehydrogenase characterize the actual rate of glycolysis in yeast, the same being true, in part, for pyruvate decarboxylase. The activity of phosphofructokinase is nearly insensitive to the oxygen level at normal tensions. The activity of the cell to the phosphofructokinase can be limited in anaerobic conditions by its scarcity. The insensitivity of glucose‐6‐phosphate dehydrogenase to the oxygen tension together with its low activity suggests that this enzyme plays primarily a biosynthetic role and that the function of the pentose phosphate pathway as an energy‐producing route is negligible.
The kinetics of protein salting‐Out: Precipitation of yeast enzymes by ammonium sulfate
Authors: Foster P. R. , Dunnill P. , Lilly M. D.
Published: December 2004

Protein solubility can be adequately represented by the classical Cohn equation for the salting‐out of alcohol dehydrogenase and fumarase from clarified yeast homogenate with ammonium sulfate. However, the constant β in this equation is a function of the contacting procedure employed. The kinetics of continuous salting‐out were similar for alcohol dehydrogenase and fumarase. The overall rate equation for precipitation had a variable order which was high initially, up to 3.1, but approached unity on completion of precipitation. This was followed by a partial resolution stage which was first order with respect to the concentration driving force. Precipitate particle size was estimated as 0.5 to 5 μm with continuous flow precipitation producing the largest particles.
Growth kinetics of a yeast grown on glucose or hexadecane
Authors: Mason T. J. , Millis N. F.
Published: December 2004

The kinetics of growth of a Torulopsis sp. was investigated in a continuous culture with glucose or hexadecane as the carbon source; growth was limited by either carbon or nitrogen. The relationship between the concentration of the limited substrate and the steady‐state growth rate of the organism was examined and tested against various models of growth. No existing model was found to describe the growth accurately and a new model has been proposed:

It is postulated that this behavior would result from a simple first order reaction between the reactants of the rate‐limiting enzymic reaction of the organism's metabolism.
External mass transfer in a biological film reactor
Authors: La Motta Enrique J.
Published: December 2004

A method for calculating the mass transfer coefficient in a biological film system, under turbulent flow conditions, is presented. It is experimentally found that fluid velocity has a positive effect on the rate of substrate utilization when the system is operated in other than the kinetic regime. A correlation is developed which indicates a dependence of the mass transfer coefficient on the fluid velocity raised to the 0.7 power.
Use of a tapered fluidized bed as a Continuous bioreactor
Authors: Scott Charles D. , Hancher Charles W.
Published: December 2004

Reactor systems based on tapered fluidized beds are being developed for aqueous bioprocesses in which adhering microorganisms or immobilized active biological fractions are used. The use of a fluidized bed prevents biomass buildup, accommodates particulates in the feed stream, is compatible with gas sparging, and allows easy removal or addition of the active materials. The tapered reactor tends to stabilize the fluidized bed, thus allowing a much wider range of operating conditions. Preliminary experimental results and an empirical mathematical model of the tapered bed indicate that bed stability is associated with a decreasing velocity and void‐fraction profile up the bed and the pressure drop across the bed decreases with increasing flow rates.

The tapered fluidized bed bioreactor is being evaluated for use in the enzymatic production of hydrogen, microbiological denitrification, and microbiological degradation of coal conversion aqueous waste streams. The enzyme catalyzed conversion of lactose to glucose and galactose was used in the evaluation of the reactor concept.
Photosynthetic regeneration of ATP using bacterial chromatophores
Authors: Pace Gary W. , Yang Ho Seung , Tannenbaum Steven R. , Archer Michael C.
Published: December 2004

We have demonstrated the use of bacterial chromatophores for the continuous photosynthetic regeneration of ATP from ADP in an ultrafiltration reactor. Biphasic kinetics of the degradation of chromatophore activity are described. Using chromatophores in combination with the enzyme adenylate kinase, we have also demonstrated continuous regeneration of ATP from AMP.
Preparation and properties of bacterial chromatophores entrapped in polyacrylamide
Authors: Yang Ho Seung , Leung Kwan‐Hang , Archer Michael C.
Published: December 2004

The immobilization of Rhodospirillum rubrum chromatophores was successfully performed by entrapping them in polyacrylamide. Their photophosphorylating activity was about 40% of native chromatophores. The temperature and pH optima for immobilized chromatophores were similar to the native photosynthetic apparatus and kinetic parameters showed that the rate of photophosphorylation in polyacrylamide particles was diffusion controlled. Light penetration of the gel particles was not a limiting parameter. Immobilization considerably increased the stability of the chromatophores towards denaturation.
Automatic membrane‐filtration system for the “on‐demand” supply of large volumes of sterile medium in continuous culture
Authors: Larsen V. F. , Spivey M. , Holdom R. S.
Published: December 2004

The construction and use of an automated membrane filtration system is described which produces 300 liters per day of sterile medium over at least four months of continuous fermentation. The capacity of the system is limited only by choice of filter type and has applications in continuous pilot plant work or medium‐scale batch fermentation, in the bulk supply of communally used laboratory medium, in supplying banks of small‐scale continuous fermentors, and for remote control of medium supply in hazardous fermentations (e.g., methane) with great savings in time and materials. Only two sterile storage jars are needed, irrespective of the total demand for the medium.
An automatic apparatus for continuous suspension culture with a concentrating device
Authors: Schmialek P. , Geyer Astrid , Miosga Verena , Nündel M. , Zapf B.
Published: December 2004

A chemostat in which mammalian cells can be raised in continuous suspension culture is described. It is constructed from commercially available parts. This apparatus has the advantage over earlier models in that the medium can be pumped off free of cells, thus suddenly increasing the cell concentration in the culture. The apparatus has been successfully used in studies on contact inhibition.
Oxygen electrode response lag induced by liquid film resistance against oxygen transfer
Authors: Linek V. , Vacek V.
Published: December 2004

The response of a polarographic oxygen electrode to a step change and to an exponential change in bulk oxygen concentration was studied theoretically and experimentally for the case where there is a significant liquid film resistance at the outer side of the membrane‐covered electrode. The probe response has been described by a mathematical model which takes into account the oxygen mass transfer through the liquid film and through the membrane. It is shown that substantial error could be introduced by neglecting the liquid film resistance. A test procedure is suggested to evaluate the error significance.
Immobilization of enzymes based on hydrophobic interaction. II. Preparation and properties of an amyloglucosidase adsorbate
Authors: Caldwell Karin Dahlgren , Axén Rolf , Bergwall Margareta , Porath Jerker
Published: December 2004

Amyloglucosidase from Aspergillus niger (α‐1,4 and 1,6 glucan glucohydrolase, EC 3.2.1.3) was immobilized through adsorption onto a hexyl–Sepharose, containing 0.51 mol hexyl‐group per mole of galactose.

The adsorption limit of the carrier with respect to this enzyme was about 17 mg per gram wet conjugate. The retention of activity upon immobilization was high, varying from essentially full activity at low enzyme content down to 68% at the adsorption limit.

The immobilized preparation, as well as the soluble enzyme, showed apparent zero order kinetics within 60% of the substrate's conversion limit. Product inhibition of the soluble enzyme showed a k1 of 5 · 10−2M.

In the presence of 3M NaCl, adsorbates were formed more rapidly and with a higher yield of immobilized protein, but with lower specific activity. Conjugates resulting from adsorption of amyloglucosidase in identical concentrations, but at different salt contents, showed comparable activities and operational stabilities. Continuous operation for three months reduced conjugate activity to 40%.

The thermal stability of the adsorbate was inferior to that of the soluble enzyme, but was noticeably enhanced in the presence of substrate.
Immobilization of enzymes based on hydrophobic interaction. III. Adsorbent substituent density and its impact on the immobilization of β‐amylase
Authors: Caldwell Karin Dahlgren , Axén Rolf , Bergwall Margareta , Olsson Ingmar , Porath Jerker
Published: December 2004

Hexyl‐groups have been introduced into crosslinked Sepharose 6B, yielding gels with degrees of substitution which range from 0.02 to 0.70 mol hexyl‐side chain per mole galactose residue.

The gels were exposed to β‐amylase in solution, and the resulting adsorbates indicated a monotonic increase in adsorption capacity with an increasing hexyl‐content. Adsorbate activity, by contrast, displayed a maximum for a carrier gel with a hexyl–galactose ratio of 0.51. Adsorbates based on gels with different hexyl‐content were used in column reactors for continuous maltose production from a soluble starch substrate.
A unique biopolymer from Rhinocladiella mansonii NRRL Y‐6272: Production in 20 liter fermentors
Authors: Burton K. A. , Cadmus M. C. , Lagoda A. A. , Sandford P. A. , Watson P. R.
Published: December 2004

The black yeast‐like fungus Rhinocladiella mansonii NRRL Y‐6272 elaborates an extracellular polysaccharide composed of N‐acetyl D‐glucosamine and N‐acetyl D‐glucosaminuronic acid residues in a 2:1 molar ratio. Production of this polymer was studied in 300 ml flasks and 20 liter fermentors. On the basis of glucose utilized, 13% conversion to polymer was obtained in four days at 25°C in medium containing yeast autolysate paste, K2HPO4, MgSO4, ZnSO4, L‐asparagine or urea, and D‐glucose. Nitrogen sources, aeration, agitation, temperature, and salts affected yields.

The polymer in diluted fermentation broths was precipitated with ethanol in the presence of an electrolyte and collected by centrifugation. The viscosities of aqueous resolutions containing 1 and 1.5% of the polymer were 9400 cP and 21,500 cP, respectively.
A method for increasing cellulase production by Trichoderma viride
Authors: Sternberg David
Published: December 2004

A doubling of cellulase production by Trichoderma viride (QM9414) is possible by increasing the cellulose concentration in the medium from 0.75 to 2%, increasing the nitrogen concentration, and controlling pH during growth. A four‐to fivefold increase in β ‐glucosidase is found with the higher cellulose concentration. Culture filtrates from 2% cellulose cultures can reduce the hydrolysis time in a practical saccharification to one‐half that required by culture filtrates from 0.75% cellulose cultures.
A silicone polymer as a Steroid Reservoir for enzyme‐catalyzed Steroid reactions
Authors: Bhasin Devinder P. , Gryte Carl C. , Studebaker Joel F.
Published: December 2004

Since steroids are only slightly soluble in the aqueous solutions in which enzymatic reactions take place, it is difficult to obtain high effective concentrations per unit reactor volume when enzymes are used to catalyze steroid reactions. In order to obtain high effective concentrations in the present work, we have used small particles of a hydrophobic polymer, poly (dimethyl siloxane), as a reservoir for the steroid substrate and product. The activity of a bacterial hydroxysteroid dehydrogenase in a buffer solution declines much more slowly in the presence of those polymer particles than in the presence of a comparable amount of butyl acetate or ethyl acetate, the organic solvents used as steroid reservoirs in previous work with steroid transforming enzymes. When another substrate of the hydroxysteroid dehydrogenase is loaded into the polymer particles and the particles are suspended in an aqueous solution containing the enzyme and its cofactor, more product is formed that when a similar solution is emulsified with butyl acetate.
Cell concentration control by viscosity
Authors: Shimmons B. W. , Svrcek W. Y. , Zajic J. E.
Published: December 2004

The apparent viscosity of baker's yeast suspensions was employed to control the cell concentration of the mixing of baker's yeast and distilled water. The apparent viscosity of baker's yeast was found to be a function of cell concentration and independent of the flow rate through the rotational viscometer. The viscometer and mixing unit were found to have first order dynamics. The open loop dynamics of the control system were nonlinear but could be linearized for small perturbations. The control system was employed to successfully control the cell concentration but exhibited nonlinear behavior.
Sliding controller design for a nonlinear fermentation system
Authors: Suárez‐Cortez Rodolfo , Alvarez‐Gallegos Jaime , González‐Mora Estela
Published: December 2004

The design of a sliding controller for a continuous fermentation process is presented. The results obtained by simulation have proved the control scheme to be very robust. Regulation of substrate concentration at its optimal value has been achieved even though process parameters change their nominal values. Chattering effects are decreased by introducing a minor modification of the control variable around the sliding surface.