bluuebunny/crossref_metadata_2025 huggingface dataset:
Composting conversion of solid wastes for mushroom growing
Authors: Block S. S.
Published: May 2005

Methods for composting small quantities of organic materials have been developed in order to be able to better study the composting process. A composting bin was developed which holds 27 cu. ft. of compost and which provides uniform conditions of temperature, moisture, and aeration within the compost mass. A system for indoor composting of less than one cubic foot of material has been developed and is described. The methods have been shown to be reliable and reproducible. The composts were evaluated for their suitability for mushroom growing and were found to give high yields of mushrooms.
Steam sterilizable probes for dissolved oxygen measurement
Authors: Johnson Marvin J. , Borkowski John , Engblom Curt
Published: May 2005

Steam‐sterilizable membrane probes for monitoring the dissolved oxygen level in fermentors, or the oxygen content of gas streams, are described. The probes have a silver cathode, a lead anode, and an acetate buffer as an electrolyte. The membrane is Teflon. The current output of the probes in the absence of oxygen is negligible.
An automatic aeration control system for biosynthetic processes
Authors: Lengyel Z. L. , Nyiri L.
Published: May 2005

An automatic aeration controller was constructed to assure the optimal amount of oxygen for aerobic biosynthetic processes. A platinum electrode and a KCl bridge for the calomel electrode were inserted hermetically into the fermentor and were sterilized with the culture medium. The electrode potential developed at the surface of the Pt electrode continuously indicated the actual oxygen concentration of the medium. This served as the controlled variable of the system. The concentration of dissolved oxygen resulted from the actual demand and supply of the microorganism. The electrode potential, which was the measured variable of the process, operated a closed‐loop automatic aeration system. The controller activated an air inlet valve in order to balance the controlled variable. The automatic controller operated in fermentors of industrial scale for long periods in a satisfactory manner.
Resistance of microorganisms to hydrostatic pressure
Authors: Timson W. J. , Short A. J.
Published: May 2005

A small fraction, about 0.05%, of the microorganisms in milk are resistant to pressure to at least 150,000 p.s.i. The pressure‐resistant microorganisms were shown to be mainly bacterial spores. Some of the pressure‐resistant organisms were identified. The lethal effect of pressure is more pronounced in the solid phase than in the liquid phase of water. B. subtilis was found to be capable of surviving solid‐phase transitions from Ice II, III, and V to Ice I. The lethal effect of high pressure in the liquid phase of water was found not to be counteracted by an increase in temperature. The pressure resistance of B. subtilis was found to be maximum around neutral or slightly basic pH. The damaging effect of low and high pH are counteracted by sodium chloride and glucose. It is suggested that the primary mechanism of protein denaturation by pressures above 30,000 p.s.i. is ionization and formation of ionic bonds between charged groups on proteins, altering their solubility.
Isolation of bacterial polysaccharide B‐1459 through calcium hydroxide complex formation
Authors: Mehltretter C. L.
Published: May 2005

A method is described for the isolation of bacterial polysaccharide B‐1459 from aqueous dispersion as a calcium hydroxide complex. The polysaccharide is liberated in fibrous form from the complex by means of hydrochloric acid in methanol solution. Overall recovery of the polysaccharide from aqueous dispersion is 85%. Direct conversion of the insoluble calcium hydroxide complex to aqueous polysaccharide solution appears to be a low‐cost procedure for preparing viscous solutions for industrial use.
Studies on methanol oxidizing bacteria
Authors: Häggström Lena
Published: May 2005

A mixed culture of methanol oxidizing bacteria has been cultivated on simple inorganic salts medium supplemented with methanol. Optimal growth occurred at 31°C, pH 6.0–6.3, and a methanol concentration between 1 and 2 ml/1, of medium. The maximum yield was 4.5 g dw/I and the mean generation time 3.2 hr.

It was estimated that 41% of methanol carbon was converted into cell‐carbon, and that 73% of the inorganic nitrogen was converted to organic nitrogen.
Large scale production of transfer ribonucleic acids fromE. coliK‐12 MO7
Authors: Hancher C. W. , Phares E. F. , Novelli G. David , Kelmers A. D.
Published: May 2005

An engineering‐scale procedure for the recovery of 300–400 g batches of mixed transfer ribonucleic acids is described. Semicontinuous growth ofE. coliK‐12 MO7 yielded 77 kg of harvested cells in four days. Phenol extraction and ethanol precipitation recovered a crude tRNA material that was further purified by DKAE‐cellulose chromatography in runs of 1 × 106A260units each on a 6 × 30 in. column using a 240 1, gradient elution. The purified tRNAs were partially concentrated and resolved into three groups.
Physiology of, an enzyme production by, plant cell cultures
Authors: Veliky I. , Sandkvist A. , Martin S. M.
Published: May 2005

Red kidney bean (Phascolus vulgaris) cells, derived from roof, callus, were grown in suspension culture in shake flasks and in laboratory fermentors using batch and continuous batch culture techniques. The medium contained casein hydrolysate, sucrose, inorganic salts, vitamins, and growth hormones. In continuous batch culture yields of up to 171 g wet weight, (8.5 g dry weight) per liter were obtained in 7 days. Organic nitrogen was used preferentially. Growth on nitrate was considerably slower than on organic nitrogen sources. Indole acetic and naphthalene acetic acids were not essential for good growth of the cells whereas kinetin and 2, 4‐D were. The optimum pH for growth was about p11 4.5. The presence of amylase and peroxidase was detected in culture filtrates. Amylase activity was low in either the presence or the absence of starch in the medium. Peroxidase production could be related directly with growth of the culture. Maximum peroxidase yield, as measured by the guaiacol method and expressed as horse radish peroxidase, was 1.25 × 10−8 M.
Continuous enzyme processing: The isolation of prolyl‐tRNA synthetase from Phaseolus Aureus
Authors: Dunnill P. , Currie J. A. , Lilly M. D.
Published: May 2005

A pilot‐plant process has been developed for the continuous extraction and partial purification of prolyl‐tRNA synthetase from mung bean. The bean slurry was wet ground in a hammer mill, clarified by two‐stage centrifugation, and the protein in the effluent fractionated by precipitation at pH values of 5.2 and 4.2. The throughput was 13 kg dry bean/hr. The improved extraction process and reduced processing time resulted in an enzyme product with a specific activity 16 × that previously obtained in the batch process. The yield was also 50–60 times higher.
Starch conversion by immobilized glucoamylase
Authors: Bachler M. J. , Strandberg G. W. , Smiley K. L.
Published: May 2005

Glucoamylase bound to DEAE‐cellulose in 0.05 M sodium acetate, pH 4.0, is active in the conversion of starch to glucose. The activity of the DEAE‐cellulose‐bound enzyme ranges from 16 to 55% of the activity of the free enzyme. Binding of the enzyme narrows the pH optimum to approximately 4.0 and lowers the temperature optimum to 40–50°C as compared to a 60°C temperature optimum for the free enzyme. Concentrations of acetate buffer above 0.1 M disrupt the DEAE‐cellulose‐enzyme complex. Columns were used with some success for the continuous conversion of starch. Pretreatment of the starch with α‐amylase and clarification were necessary to prevent blocking of the column. Columns maintained activity for more than 3 weeks of continuous operation.
Diffusion, permeation, or enzyme limitation: A probe for the kinetics of enzyme induction
Authors: Koch Arthur L. , Coffman Robert
Published: May 2005

The 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

Two 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

Growth 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

The 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

Extensive 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

Values 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

In 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

Growth 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

A 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

The 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

Substrate 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

A 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

The 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

The 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

The 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

The 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

The 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

Serine 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

Two 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

A 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

Liquid 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

The 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.
Mechanistic analysis of complex enzyme deactivations: Influence of various parameters on series‐type inactivations
Authors: Sadana Ajit , Henley James P.
Published: May 2005

A series‐type enzyme deactivation model is used to model and to quantitate some more complex enzyme deacti‐vations. The influence of temperature, pH, immobilization, chemical modifier (inhibitor or protector), substrate, and metal ion on the inactivation kinetics and on the parameter values is examined. In some cases the influence of two parameters on enzyme inactivations is presented. This provides further physical insights into enzyme inactivation and stabilization processes.
Investigations of oxygen transfer into Penicillium chrysogenum pellets by microprobe measurements
Authors: Wittier Rüdiger , Baumgartl Horst , Lübbers Dietrich Werner , Schügerl Karl
Published: May 2005

A microcoaxial needle sensor with a tip diameter of ca. 0.7 μm was used as a microprobe to measure profiles of dissolved oxygen tension (DOT) within fixed pellets of Penicillium chrysogenum as a function of the DOT level around the pellet, in the presence and absence of bulk convective flow and turbulence. The investigations indicate that the oxygen transfer mechanism is complex. The results were interpreted by assuming the penetration convective flow into the entire pellet and penetration of turbulence into the outer range. A model was developed which was able to describe the measured DOT profiles very well. The model takes into account molecular and turbulent diffusion as well as convective flow as transfer mechanisms inside of the pellet. Structures of pellets used for microprobe measurements were evaluated by histological investigations. Considerable variations of mycelial density with radius within the pellets were found.
Thin‐film antimony–antimony‐oxide enzyme electrode for penicillin determination
Authors: Flanagan M. T. , Carroll N. J.
Published: May 2005

A potentiometric penicillinase electrode is reported in which the base pH transducer is a thin‐film anti‐mony–antimony‐oxide electrode deposited by vacuum evaporation. Several enzyme immobilization procedures have been examined and a crosslinked protein film found to be the most appropriate to this type of sensor. The use of an adjacent antimony–antimony‐oxide track as a pseudoreference electrode was successfully demonstrated. The overall response was shown to be independent of the stirring rate above 100 rpm, but the kinetics of the response were found to depend markedly on the stirring rate. The intrinsic linear response range was 3 × 10−4Mto 7 × 10−3M penicillin G. Linearizing transforms that extend the useful range were examined.
Effect of pH oscillations on a competing mixed culture
Authors: Davison Brian H. , Stephanopoulos Gregory
Published: May 2005

Two microorganisms, E. coli and S. cerevisiae, competing for glucose were maintained in a stable cycle of coexistence by alternating the growth advantage between the two organisms by oscillating the pH in a Chemostat. Pure culture experiments found S. cerevisiae to be insensitive to pH between 5 and 4.3 with a maximum specific growth rate (μmax) of 0.4/hr; while μmax of E. coli decreased from 0.6 h−1 at pH 5 to 0.1 h−1 at pH 4.3. Steady‐state and cross‐inoculation chemostat runs at a dilution rate of 0.17 h−1 confirmed the expectation that the mixed culture system is unstable at constant pH with E. coli dominating at pH 5 and S. cerevisiae dominating at pH 4.3. Three pH oscillation experiments were performed at D =0.17 h−1 with 1 g per liter glucose feed. The 16 h/16 h cycle was stable for six periods with a stable alternating cycle of E. coli and S. cerevisiae being quickly established. A 18 h pH 5/14 h pH 4.3 cycle was found to be stable with smaller yeast concentrations. A 6 h/6 h cycle was found unstable with yeast washout. Simulation results were compared with these runs and were used to predict the onset of instability. Oscillations of pH can force stable persistence of a competing mixed culture that is otherwise unstable. Thus, varying conditions are experimentally demonstrated to be one explanation for competitive coexistence.
Characteristics of lipase‐catalyzed hydrolysis of olive oil in AOT–isooctane reversed micelles
Authors: Han Daeseok , Rhee Joon Shick
Published: May 2005

Candida rugosa lipase solubilized in organic solvents in the presence of both surfactant and water could catalyze the hydrolysis of triglycerides, and kinetic analysis of the lipase‐catalyzed reaction was found to be possible in this system. Among eight organic solvents tested, isooctane was most effective for the hydrolysis of olive oil in reversed micelles. Temperature effect, pH profile, Km,app and Vmax,app were determined. Among various chemical compounds, Cu2+, Hg2+, and Fe3+ inhibited lipase severely. But the enzyme activity was restorable partially by adding histidine or glycine to the system containing these metal ions. The enzyme activity was dependent on R (molar ratio of water to surfactant) and maximum activity was obtained at R = 10.5. Upon addition of glycerol to the reversed micelles, lipase activity was affected in a different fashion depending on the R values. Stability of the lipase in reversed micelles was also dependent on R, and it was most stable at R = 5.5.
Biohydrogenation of unsaturated fatty acids by a mixed culture of rumen microorganisms
Authors: Kellens M. J. , Goderis H. L. , Tobback P. P.
Published: May 2005

The biohydrogenation of C‐18 unsaturated fatty acids was examined in a mixed culture of microorganisms prepared by inoculating a proper growth medium with a sample of rumen fluid. Some major factors influencing the hydrogenation capacity have been investigated. The age of the mixed culture, the type of inoculum used, the concentration of substrates as well as the presence of sterile rumen fluid in the growth medium were found to be important factors determining biohydrogenation behavior. It could be shown that the mixed microbial culture, which had been grown for about 24 h on a medium similar to that of Bryant and Robinson, contained sterile rumen fluid (10% v/v), and had been inoculated with a sample of the whole untreated rumen content, had the best biohydrogenation capacity. The culture was able to carry out the complete conversion of linoleic and linolenic acid to stearic acid.
Stabilization of κ‐carrageenan gel with polymeric amines: Use of immobilized cells as biocatalysts at elevated temperatures
Authors: Chao K. C. , Haugen M. M. , Royer G. P.
Published: May 2005

Spherical beads of κ‐carrageenan containing entrapped cells were prepared in a two‐step process. First, the beads were formed by dispersing a warm carrageenan cell suspension into stirring oil. After cooling (gelation) the beads were cured by treatment with amines. Ten amines of various sizes and structures were tested. We evaluated the mechanical strength and the applicability of aminetreated gels as immobilization matrices. The results of critical compression tests indicate that linear and branched polyethylenimines (PEI) are both good curing agents. PEI treated carrageenan beads also exhibited superior resistance to heat and abrasion. Furthermore, PEI polymers were demonstrated to be effective in stabilizing the lactase activity of the free and immobilized Bacillus stearothermophilus cells. The immobilized cell preparations of Saccharomyces cerevisiae, B. stearothermophilus, and Flavobacterium sp. were treated with branched PEI and evaluated for the activity of invertase (EC 3.2.1.26), lactase (EC 3.2.1.23), and glucose isomerase (EC 5.3.1.18), respectively, in a packed bed reactor at 60°C. The apparent half‐lives were 108, 39, and 64 days, respectively.
Measurement of interfacial areas in aerobic fermentations by ultrasonic pulse transmission
Authors: Stravs Andrej A. , Pittet Alain , von Stockar Urs , Reilly Peter J.
Published: May 2005

The penetration of ultrasonic waves through opaque media and the large difference in the acoustic properties between air bubbles and the fermentation broth were used to measure the energy attenuation of pulsed ultrasound by the bubbles as the waves passed through the broth. This leads to an on‐line determination of the specific interfacial area provided information is available about the holdup or bubble mean diameter. This article gives the principle of the method and demonstrates how the measured interfacial area may be used in evaluating the mass transfer coefficient of a fermentation system in a bubble column.
Coimmobilization of substrate and biocatalyst: A method for bioconversion of poorly soluble substances in water milieu
Authors: Kaul Rajni , Adlercreutz Patrick , Mattiasson Bo
Published: May 2005

Coimmobilization of biocatalyst and substrate was studied as a method to increase the conversion rate in systems with substrates of extremely low solubility in water. The system studied was the conversion of hydrocortisone to prednisolone by Arthrobacter simplex. As a matrix for coimmobilization, alginate turned out to be superior to agar and agarose. After the reaction was complete, the beads were solubilized, andthe cells recovered for reuse, by centrifugation, whereas the prednisolone was extracted from the supernatant.
An investigation of the efficacy of biological additives for the suppression of pyritic sulphur during simulated froth flotation of coal
Authors: Stainthorpe A. C.
Published: May 2005

The biological molecule responsible for the suppression of pyritic sulfur in fine coal simulated froth flotation treated with bacteria was identified. Protein was found to be the most effective agent in pyrite suppression of the three cell components (protein, lipid, and carbohydrate) assayed. Coal recovery and ash removal of the flotation process were only slightly reduced by this treatment. Other protein‐containing materials were evaluated for their ability to suppress pyrite flotation. Whey was found to be the most cost‐effective flotation additive of those assayed. The sulfur content of the whey‐treated float was reduced by 84.0% in a synthetically prepared fractionated coal (10.7% sulfur), by a raw whey dosage of 20 μL/g coal. The inorganic sulfur component of a natural high sulfur coal fraction (10.9%) was completely depressed by this whey addition. The effect of particle size and pulp density upon the process were investigated.
Osmotic, biomass, and oxygen effects on the growth rate of Fusarium oxysporum using a dissolved‐oxygen‐controlled turbidostat
Authors: de la Broise Denis , Durand Alain
Published: May 2005

The system described is a modified Hospodka's turbidostat. This device helps to measure the maximum growth rate of fungi in steady‐state aerobic conditions with defined and independent concentration of dissolved oxygen, biomass, and substrate even unlimited. The principle consists of a turbidostat controlled by the dissolved oxygen concentration. The inlet medium pump operates when the dissolved oxygen concentration falls below the set point value. This method allows us to study independently effects of different physical and chemical variables on the maximum specific growth rate of microorganisms. A fungus, Fusarium oxysporum 47 isolated from soil, does not show a depressive effect on growth when dissolved oxygen concentration decreases to 5% and osmotic potential to ‐25 bars. Increasing biomass concentration in the range 0.1‐1.0 g/L appears to depress markedly the maximum growth rate.
Effect of environmental growth conditions on plasmid stability, plasmid copy number, and catechol 2,3‐dioxygenase activity in free and immobilized Escherichia coli cells
Authors: Sayadi S. , Nasri M. , Barbotin J. N. , Thomas D.
Published: May 2005

In order to better understand the high plasmid stability in immobilized recombinant E. coli cells, the effects of dilution rate on the pTG201 plasmid stability, the copy number, and the catechol 2,3‐dioxygenase (encoded by XyIE gene) production were, at first, studied in free E. coli W3101 continuous cultures in minimal media. It was found that decreasing specific growth rate increased the plasmid copy number and the catechol 2,3‐dioxygenase activity but the stability decreased. In continuous culture with immobilized cells, an increase was shown in plasmid copy number and catechol 2,3‐dioxygenase activity probably due to the distribution of growth in the gel beads. Besides mechanical properties of gel beads which may allow limited cell divisions, the increase in plasmid copy number is involved in enhanced plasmid stability in immobilized cells. In the same way, an experiment conducted in LB medium dealing with competition between pTG201‐free and pTG201‐containing E. coli B cells was described. It was shown that the competition was not more pronounced in gel bead compared to a free system. The effects of nutritional limitations on pTG201 plasmid stability and catechol 2,3‐dioxygenase activity during chemostat cultivations in free and immobilized E. coli B cells were also investigated. It was found that immobilization of cells increased the stability of pTG201 even under glucose, nitrogen, or phosphate limited cultures. However in the case of magnesium depleted culture, pTG201 was shown to be relatively instable and a decrease in viable cell number during the immobilized continuous culture was observed. By contrast to the free system, the catechol 2,3‐dioxygenase activity increased in immobilized cells under all culture conditions used.
Destruction and formation of toxins by one bacterial species affect biodegradation by a second species
Authors: Murakami Yoshitaka , Alexander M.
Published: May 2005

Two strains of Pseudomonas able to grow on phenol or p‐nitrophenol (PNP) were isolated from sewage. Pseudomonas sp. PN101 mineralized and formed nitrite from PNP but did not mineralize phenol, and Pseudomonas sp. PH111 mineralized phenol but not PNP. Phenol increased the lag period before Pseudomonas sp. PN101 grew on and mineralized PNP, but this toxicity was reduced by inoculation of the medium with Pseudomonas sp. PH111. PNP inhibited growth of Pseudomonas sp. PH111 and slightly increased the length of the acclimation period for the mineralization of phenol by the bacterium. Inoculation of Pseudomonas sp. PN101 into solutions containing PNP and phenol increased the lag period prior to growth of Pseudomonas sp. PH111 on phenol and markedly lengthened the lag period for its mineralization of phenol. Coinciding with this delay in the onset of phenol degradation was the accumulation of an organic compound formed from PNP by Pseudomonas sp. PN101. This compound was not mineralized by the phenol‐degrading bacterium. The data suggest that bacteria may interact during the decomposition of chemical mixtures by destroying or by forming toxins that affect the biodegradation of individual components of those mixtures.
Performance of a membrane reactor for cellobiose hydrolysis
Authors: Pizzichini M. , Fabiani C. , Adami A. , Cavazzoni V.
Published: May 2005

A continuous enzymatic hollow fiber reactor (HFR), obtained by immobilizing cellobiose active cells into the shell side of hollow‐fiber modules, was studied. The HFR yield was monitored by glucose analysis resulting from hydrolysis of cellobiose. The residence time of substrate in the bioreactor to obtain convenient hydrolysis yields was calculated from tests carried out by varying the reactor dilution rate in the range 0.001–0.004 L/min. The glucose yield was measured for 300 h (continuous substrate flux). The yield decreased from 40 to 15%. This decrease was due to the loss of specific activity in the operating conditions and to the pressure drop increase from 0.2 to 1.7 atm. The pressure drop increase is in turn dependent on the cell loading (0.2–2.1 g dry cell) and the substrate flux.