bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diffusion, permeation, or enzyme limitation: A probe for the kinetics of enzyme induction
Authors: Koch Arthur L. , Coffman Robert 
Published: May 2005

AbstractThe utilization of an exogenous substrate by enzyme inside a bacterial cell can be limited by diffusion up to the cell, penetration of the cell, diffusion within the cell, and/or attack by internal enzyme. For small molecular weight substrates such as galactosides, and for bacteria such as Escherichia coli the diffusion steps are not rate limiting even with the permeases fully induced and the external concentration of substrate low. In permeaseless organisms with more than about 20 enzyme molecules per cell, permeation of O‐nitrophenyl‐β‐D‐galactoside through the membrane is limiting. Thus, a single initiation of transcription of a lactose message suffices to yield enough enzyme molecules to switch an uninduced cell from enzyme limitation to permeability limitation. Subsequent initiations change the cellular activity very little. This transition can be followed by assaying enzyme activity of both intact and lysed cell suspensions. In this way the induction response amongst cells in growing populations at high inducer concentrations has been found to be uniform. It was found that nearly all of the cells from balanced growing culture are immediately inducible even with doubling times as short as 7.6 hrs. At 24 hrs about 1/3 of the cells are inert at any time, but all cells synthesize enzyme within a 3‐hour period. At low inducer concentration or in the present of catabolite repressor the rate of initiation is greatly decreased; this leads to a non uniform distribution of enzyme within the cells, which is readily detected by the experimental technique. In addition to developing the kinetics for enzyme contained in cells, the distribution of the enzyme among uninduced bacteria is presented.
Optimization of batch fermentation processes. I. Development of mathematical models for batch penicillin fermentations.
Authors: Constantinides Alkis , Spencer Jordan L. , Gaden Elmer L. 
Published: May 2005

AbstractTwo kinds of mathematical models have been developed for batch penicillin fermentations: (1) general models, based on averaged, nondimensionalized cell and penicillin synthesis curves from plant, scale fermentors and (2) particular models developed from specific sets of experimental data from two sources. Parameter‐temperature functions used with the general models were assumed to have general shapes which could apply to many fermentations, i.e., they were based on the familiar temperature response of enzyme‐catalyzed reactions. Parameter‐temperature functions for the particular models were determined from experimental data for batch runs at various temperatures.
Growth and acid production by Lactobacillus (L.) delbrueckii in a dialysis culture system
Authors: Friedman Morton R. , Gaden Elmer L. 
Published: May 2005

AbstractGrowth and lactic acid production by L. delbrueckii was studied in a dialysis culture system and the inhibitory effect of lactate confirmed by removing lactate from the culture medium by dialysis. It has been shown that lactate inhibits growth after the log phase and that the maintenance of low lactate concentrations after this point permits higher specific growth rates and higher maximum cell concentrations. Acid production is also significantly higher in a dialysis culture system. Finally, a modification of the Luedeking‐Piret model, incorporating the lactate inhibition effect, is proposed.
The response by microorganisms to steady‐state growth in controlled concentrations of oxygen and glucose. II. Saccharomyces carlsbergensis
Authors: Moss F. J. , Rickard Pamela A. D. , Bush F. E. , Caiger P. 
Published: May 2005

AbstractThe growth of Saccharomyces carlsbergensis in continuous culture has been studied when dissolved oxygen and glucose concentrations were held constant at a series of steady‐state levels. Both oxygen and glucose controlled the degree of aerobic metabolism and of ethanolic fermentation. When the glucose uptake rate was low (between 1.2 and 2.8 mmoles per hour per gram of yeast) the relative distribution of glucose between ethanolic and aerobic fermentation was sensitive to oxygen: when dissolved oxygen was near to saturation, glucose metabolism was 0.98 aerobic; when dissolved oxygen was 0.01 saturated, 0.8 of intake glucose metabolism was by ethanolic fermentation. On the other hand when glucose intake was high (between 7.6 and 18.2 mmoles) metabolism was predominately by ethanolic fermentation even when dissolved oxygen concentration was at saturation. The extent, to which catabolism proceeded by an anaerobic or aerobic pathway, as judged by ethanol production, was controlled more by the uptake of glucose than of oxygen.
Utilization of cellulose from waste paper by Myrothecium verrucaria
Authors: Updegraff David M. 
Published: May 2005

AbstractExtensive screening studies on cellulolytic bacteria and fungi led to the selection of Myrothecium verrucaria as the organism producing the maximum rate of protein biosynthesis from ball‐milled newspaper. Studies in aerated stirred‐jar fermentors were carried out to determine the conditions for maximum protein synthesis rate and maximum final protein concentration. The optimum aeration rate was 250 to 374 mM of oxygen at 300 to 400 rpm stirring rate. The pH optimum was broad, from 3.9 to 6.5. Urea at 0.03% and yeast autolysate at 0.1% stimulated growth rate and protein production. The maximum rate of protein biosynthesis and the maximum protein yield were 0.3 g/liter/day and 1.42 g/liter, respectively, from medium G3 with 4% ball‐milled newspaper. The final product, obtained by evaporation of the total culture, was 33.7 g from one liter of medium which originally contained 40 g of ball‐milled newspaper and 11.3 g of other dissolved materials. The protein content of this final product was 3.3 g, calculated from total organic N × 6.25 or 1.42 g calculated from the biuret method. Both the synthesis rate and the final cell yield are below those obtainable by growing Fungi Imperfecti, yeasts or bacteria on soluble materials such as glucose.
Variability in cell yield for heterogeneous microbial populations of sewage origin grown on glucose
Authors: Gaudy A. F. , Ramanathan M. 
Published: May 2005

AbstractValues of cell yield collected over a period of eight years for heterogeneous populations of sewage origin acclimated to glucose in both batch and continuous culture were subjected to statistical analysis. The cell yield for this sole source of carbon (glucose) ranged from 36 to 88 per cent in batch culture, and 32 to 69 per cent in continuous culture. Because experimental conditions were known and well defined, the variability in cell yield is attributable to the ecological variation inherent in a heterogeneous population. The data presented demonstrate the futility of attempts to define Y for such populations as a precise theoretical constant dependent upon thermodynamic properties of the substrate.
Steady‐state model for activated sludge with constant recycle sludge concentration
Authors: Ramanathan M. , Gaudy A. F. 
Published: May 2005

AbstractIn a previous report it was concluded that steady‐state operation of completely mixed reactors for growth of heterogeneous microbial populations, i.e., activated sludge processes, was extremely difficult to attain if maintenance of a constant sludge recycle ratio, c, was required, and equations were devised in which the concentration of cells in the recycle, xR, rather than the recycle ratio, was constant. In this report the equations are developed and computational analysis shows the effect on substrate and cell concentrations in the reactor of operational variables such as inflowing feed concentration, hydraulic recycle ratio, recycle sludge concentration, dilution rate, and the biological “constants” μm, ks, and Y. The stabilizing effect of operating with constant xR on the dilute‐out pattern is shown.
Mechanism of uptake of liquid hydrocarbons by microorganisms
Authors: Yoshida Fumitake , Yamane Tsuneo , Yagi Hideharu 
Published: May 2005

AbstractGrowth rates of Candida tropicalis were studied in two different fermentors. One was the ordinary shaker flask containing both the aqueous culture medium and liquid hydrocarbons. The other was a specially designed rotating disk‐type fermentor containing only the aqueous culture medium, into which vapors of n‐paraffins from C6 to C18 were supplied continuously without forming the liquid hydrocarbon phase. The specific growth rates of Candida tropicalis in the rotating disk fermentor, under such conditions that supply of hydrocarbon vapor was sufficient, showed good agreement with those in the shaker flask. This seems to indicate that hydrocarbon uptake by Candida tropicals by direct contact with liquid hydrocarbon is negligible.
Conversion of 5′xanthylic acid to guanine and guanine nucleotides by a mutant of Brevibacterium ammoniagenes
Authors: Furuya Akira , Abe Shigeo , Kinoshita Shukuo 
Published: May 2005

AbstractA decoyinine resistant, KY 13501, isolated after nitrosoguanidine treatment from Brevibacterium ammoniagenes ATCC 6872 converted 5′XMP added in fermentation media to guanine derivatives and accumulated them in the media. The converted substances were identified as guanine, 5′GMP, 5′GDP, and 5′GTP. The conditions for the conversion were examined and the following points were clarified. (1) Very low concentration of manganese ion (Mn2+) showed profound effects on the conversion and the excessive amounts of the ion severely repressed the conversion. (2) Under limitation of Mn2+, 5′XMP was converted most efficiently when added at inoculation time. (3) The inhibition of the conversion by excessive amount of Mn2+ was completely released by addition of a surface activating agent, polyoxyethylene stearylamine. (4) For the conversion, it was essential to maintain pH of the media at 7.5 to 8.0 and supply ammonium ion.
A mathematical model for RNA bacteriophage production in batch culture
Authors: Chen Michael S. K , Nagai Shiro , Humphrey Arthur E. 
Published: May 2005

AbstractThe interaction between male‐specific RNA phages and bacterial cells as well as the complete life cycle of RNA phages in the host cells are complicated phenomena. In this study, a mathematical model is proposed to describe the kinetics of RNA phage production in batch culture. The model consists of several important considerations: (1) adsorption and desorption of phages on cell pili, (2) injection and transport of viral RNA, (3) viral protein synthesis, (4) phage maturation, and (5) cell lysis.Experimental data of MS2 RNA phage production in E. coli C 300o bacteria culture were used to evaiuate the model parameters. Reasonably good fit was obtained between the model and one set of data. However, simulation study based on the estimated parameter values revealed a discrepancy between experimental observation and model prediction. It seems that variation both in F‐piliation and in the competence of cells to be infected by phages through different phasae of growth must be taken into account in order to make the model useful.
Steady‐state stability of substrate inhibited enzyme catalysis in open reaction systems
Authors: O'Neill S. P. 
Published: May 2005

AbstractSubstrate inhibited enzyme reactions occurring in systems open to mass transfer may display multiple steady‐state behavior. For a simple one‐substrate case it is shown theoretically that the unstable steady‐state region always lies within the conversion range of 50–100%. A criterion for the stability of a steady‐state point is given. Numerical solutions of the appropriate transient equation show how the system approaches stable steady state in instances where there are three possible steady‐state points. The consequences of the existence of an unstable region on the systems response to changes in its parameters is discussed.
Spectrophotometric methods for monitoring the microbial transformation of steroids. II. Absorbance ratio spectrophotometric determination of per cent conversion of 9α‐fluoro‐16α‐hydroxyhydrocortisone to 9α‐fluoro‐16α‐hydroxyprednisolone
Authors: Ivashkiv Eugene 
Published: May 2005

AbstractA process method has been developed for estimating rapidly the conversion of 9α‐fluoro‐16α‐hydroxyhydrocortisone to 9α‐fluoro‐16α‐hydroxyprednisolone in fermentation broths. This allows frequent analyses of samples during the fermentation cycle. The absorbance ratio determination of conversion of the steroids is based on the measurement of the absorbance of aqueous steroid borate complexes at 241.5 mμ and 271 mμ.
Temperature relationship in continuous culture
Authors: Topiwala H. , Sinclair C. G. 
Published: May 2005

AbstractThe steady‐state and transient behavior of a chemostat‐type continuous culture ofAerobacter aerogeneswas investigated with special reference to temperature. Experimentally determined kinetic parameters of the fitted steady‐state model were found to be strong functions of temperature. The transient response of the culture to a step change in temperature exhibited a dynamic lag whose magnitude depended on the nature and direction of step change.
Symbiotic growth of Acetobacter suboxydans and Saccharomyces carlsbergensis in a chemostat
Authors: Chao Chih‐Cheng , Reilly Peter J. 
Published: May 2005

AbstractThe bacterium Acetobacter suboyxdans and the yeast Saccharomyces carlsbergensis have been grown together on a synthetic medium in a chemostat. Mannitol, the only carbon source fed to the fermenter, is oxidized by the bacteria to fructose. The yeast, which cannot attack mannitol, breaks down the fructose nearly completely. Eight steady states and five transitory periods after changes in flow rate have been analyzed to study the kinetics of the mixed culture. Separate cell concentrations were determined by a modified Coulter counter apparatus. Both sugars were monitored. Both bacteria and yeast may be modeled using Monod's equation, the latter with some deviations. The yeast is unable to grow beyond the washout point of the bacteria, even though its maximum growth rate is much higher. The yield of both organisms decreases with increasing dilution rate, as does their average cell size. After step changes in dilution rate, repeated oscillations of both sugar and cell concentrations usually occur before steady‐state conditions are reattained. They are generally in phase, with no definite sign of a lag. Oscillations of yeast and fructose concentrations are more pronounced. Periods average about 6 hr and are not correlated with fermentation conditions or equipment variables. Repeated oscillations are not found after step‐downs in pure cultures of A. suboxydans, leading to the conclusion that the instability in mixed cultures may be caused by a feedback mechanism from the yeast to the bacteria.
Intensification of oak sawdust enzymatic hydrolysis by chemical or hydrothermal pretreatment
Authors: Szczodrak J. , Llczuk Z. , Rogalski J. , Leonowicz A. 
Published: May 2005

AbstractThe activities of cellulases and xylanase were determined in laboratory cultures of Aspergillus terreus F‐413 performed on natural and chemically or hydrothermally pretreated oak sawdust. The best stimulation effects were obtained in the cultures containing sawdust treated with dioxane, sodium hydroxide, or phosphoric acid. Moreover, the sawdust pretreatment distinctly affected its enzymatic hydrolysis, especially when the preparation of hydrolase complex was isolated from the culture of A. terreus F‐413 growing on the modified sawdust as a sole carbon source. The highest saccharification effect was observed when the sawdust was treated with dioxane, sodium hydroxide, or phosphoric acid. Glucose was the main product of sawdust decomposition found in the hydrolyzates.
The inhibition of the maximum specific growth and fermentation rate of Zymomonas mobilis by ethanol
Authors: Jöbses I. M. L. , Roels J. A. 
Published: May 2005

AbstractThe inhibition of the maximum specific growth and fermentation rate of Zymomonas mobilis by ethanol was studied in turbidostat cultures at constant and stepwise changed ethanol concentrations. Up to 50 g/L ethanol, the inhibition kinetics can be approximated by a linear relationship between the specific growth rate and the ethanol concentration. Above this level, deviations from this linearity are observed. The specific fermentation rates were less inhibited by ethanol than was the specific growth rate. The maximum ethanol concentration achieved was 72 g/L.The response time for the adaptation of a turbidstat culture to step changes in the ethanol concentration was markedly dependent on the concentration level, the response time being large at high ethanol concentrations.
Butanol fermentation liquor production and separation by reverse osmosis
Authors: Garcia Albert , Iannotti Eugene L. , Fischer James L. 
Published: May 2005

AbstractThe problem of dilute solvent concentration in butanol‐acetone fermentations can be solved by using reverse osmosis to dewater the fermentation liquor. Polyamide membranes have a potential application in a butanol‐acetone fermentation and exhibited rejection rates as high as 98%. Optimum rejection of butanol in the fermentation liquor occurred at recoveries of 20–45%. Flux ranged from 0.05 to 0.6 L m−2 min−1.
Enzymatic production of L‐serine
Authors: Hsiao Humg‐Yu , Wei Tena , Campbell Karen 
Published: May 2005

AbstractSerine hydroxymethyltransferase (SHMT) in the form of crude extract form a recombinant strain of Klebsiella aerogenes was used to study the production of L‐serine from glycine and formaldehyde (HCHO). SHMT activity linearly increased with temperature (30–50°C). Addition of exogenous cofactors, tetrahydrofolic acid and pyridoxal–phosphate, significantly increased SHMT activity. The pH optimum of the SHMT catalyzed L‐serine synthesis step was between 8.0 and 8.5. The Km for glycine was 11.6mM at 37°C and pH 8.0. A 87% molar conversion of glycine to serine was obtained at equilibrium (37°C, pH 8.0). Tetrahydrofolic acid was stabilized by maintaining the redox potential of the reaction solution below –330 mV through the addition of a reducing reagent such as β‐mercaptoethanol. SHMT stability was very sensitive to HCHO concentration. By carefully balancing the HCHO feed rate against the enzymatic bioconversion rate in order to keep HCHO concentration low, a serine titer of 160 g/L was achieved, the residual glycine concentration was reduced to 40 g/L, a 70% molar conversion of glycine with quantitative yield was obtained, and the overall serine productivity was 5.2 g/L/h.
Anaerobic fermentation of Lactobacillus bulgaricus and streptococcus thermophilus on 3% nonfat dry milk with pure and mixed culture
Authors: Oner M. D. , Erickson L. E. 
Published: May 2005

AbstractTwo different strains of Lactobacillus bulgaricus (ATCC‐11842 and Microlife) and two strains of Streptococcus thermophilus (ATCC‐19258 and Microlife) were grown anaerobically on 3% nonfat dry milk in pure and mixed culture using batch followed by fed batch culture. Samples were collected every 30 min. Concentrations of lactose, galactose, lactic acid, and other products present were measured using high pressure liquid chromatography. A spectrophotometric method from the literature was modified and used to determine microbial biomass concentrations. Relative cell numbers of the two organisms were measured microscopically in mixed culture. The results are presented in tabular form. S. thermophilus (Microlife) showed different growth characteristics compared to the other cultures. This culture utilized most of the galactose that was formed and produced greater amounts of lactic acid and biomass.
Growth of Saccharomyces cerevisiae is controlled by its limited respiratory capacity: Formulation and verification of a hypothesis
Authors: Sonnleitner B. , Käppeli O. 
Published: May 2005

AbstractA novel mechanistic model for the growth of baker's yeast on glucoseis presented. It is based on the fact that glucose degradation proceeds via two pathways under conditions of aerobic ethanol formation. Part is metabolized oxidatively and part reductively, with ethanol being the end product of reductive energy metabolism. The corresponding metabolic state is designated oxidoreductive. Ethanol can be used oxidatively only. Maximum rates of oxidative glucose and ethanol degradation are governed by the respiratory capacity of the cells. The model is formulated by using the stoichiometric growth equations for pure oxidative and reductive (fermentative) glucose and ethanol metabolism. Together with the experimentally determinable yield coefficients (YX/S) for the respective metabolic pathways, the resulting equation system is sufficiently determined. The superiority of the presented model over hitherto published ones is based on two essential novelities. (1) The model was developed on experimentally easily accessible parameters only. (2) For the modeling of aerobic ethanol formation, the substrate flow was split into two simultaneously operating (i.e., in parallel) metabolic pathways that exhibit different but constant energy‐generating efficiencies (respiration and fermentation) and consequently different and constant biomass yields (YX/S). The model allows the prediction of experimental data without parameter adaption in a biologically dubious manner.
Effect of microorganisms on rate of liquid extraction of ethanol from fermentation broths
Authors: Crabbe P. G. , Tse C. W. , Munro P. A. 
Published: May 2005

AbstractLiquid extraction is one means of removing metabolic products continuously during a fermentation and so reducing product inhibition. It is known that microbial organisms are attracted to liquid‐liquid interfaces, and it is important for the design of extraction systems to establish if this has a detrimental effect on the rate of extraction. The extraction of ethanol from aqueous suspensions of yeast (Saccharomyces cerevisiae) using n‐ decanol is described in this paper. It was found that the presence of the yeast cells severely reduced the rate of ethanol extraction. The overall mass transfer coefficient was reduced from 5.0 × 10−6 to 0.7 × 10−6 m/s. This reduced overall mass transfer coefficient was unaffected by yeast concentration in the range 0.1–20 kg/m3. The results are consistent with the yeast cells adsorbing to the interface in closely packed layers and preventing mass transfer by simply reducing the available interfacial area. Optical microscope observations confirmed that a yeast layer several cell diameters thick rapidly built up at the interface when a small decanol droplet was added to a yeast suspension.
Effects of glucose on phenol biodegradation by heterogeneous populations
Authors: Rozich Alan F. , Colvin Richard J. 
Published: May 2005

AbstractThe effect of the presence of more easily degradable alternative carbon sources on the biodegradation of toxic waste components is of great practical importance. In this work, a mixed phenol/glucose waste was fed to two heterogeneous populations acclimated to different conditions: one was acclimated to phenol as a sole source of carbon and one to a mixed phenol/glucose substrate. Batch substrate utilization experiments were performed under both growth and nonproliferating (no medium nitrogen source) conditions in order to assess substrate removal patterns at the levels of enzyme production and enzyme function. The results indicated that the substrate removal pattern exhibited by the cells was significantly influenced by the acclimation characteristics of the culture. The phenol acclimated cells showed an initial preference for phenol, but the presence of glucose hindered phenol removal rate under both growth and nonproliferating conditions. The cells acclimated to the mixed phenol/glucose waste demonstrated rapid initial glucose removal with a slower concomitant utilization of phenol; acclimation to the mixed waste evidently had a significant impact on the substrate removal pattern for this mixed substrate system.