bluuebunny/crossref_metadata_2025_split huggingface dataset:
Production of the macrolide antibiotic tylosin in batch and chemostat cultures
Authors: Gray P. P. , Bhuwapathanapun S. 
Published: December 2004

AbstractThe production of tylosin and related compounds by Streptomyces fradiae NRRL 2702 was studied in batch and chemostat cultures using a soluble synthetic medium. In batch culture, a trophophase–idiophase kinetic pattern was observed with tylosin, macrocin, and relomycin accumulating in the idiophase. When the organism was grown in chemostat culture, the specific rate of production of tylosin and related compounds (qtylosin) was found to be a function of the growth rate. The maximum value of (qtylosin) was observed when D = 0.017 hr−1. At this growth rate only tylosin and relomycin accumulated in the medium. By varying the concentration of glucose in the ingoing medium it was possible to study the effects of glucose on tylosin synthesis in chemostat cultures. At a growth rate of 0.017 hr−1, the maximum value of qtylosin was 0.71 mg tylosin/g dry weight (DW)/hr when the glucose uptake rate was 7 mg glucose/g DW‐hr. This value of qtylosin was 40% greater than the maximum qtylosin observed in batch culture. When glycerol was substituted for glucose in the medium, it was possible in chemostat culutures to get values of qtylosin approximately 20% greater than those obtained with glucose at the same uptake rate. By varying the concentration of sodium glutamate in the ingoing medium it was possible to show that increasing the specific uptake rate of sodium glutamate increased the values of qtylosin obtained. Similar chemostat experiments where the inorganic phosphate concentration in the ingoing medium was varied showed that increased the uptake of phosphate decreased the values of qtylosin obtained. Also increasing the uptake rate of phosphate increased the relomycin‐to‐tylosin ratio. By taking into consideration the suppressing effects of glucose and the stimulating effects of sodium glutamate on tylosin synthesis, it was possible to formulate a medium that resulted in a value of qtylosin of 1.1 mg/g/hr being obtained at a growth rate of 0.03 hr−1. Batch fermentations with this medium did not follow a trophophase–idiophase kinetic pattern, but instead tylosin was actively synthesized during a period of rapid mycelial growth.
A quantitative description of the growth of Saccharomyces cerevisiae CBS 426 on a mixed substrate of glucose and ethanol
Authors: Geurts Th. G. E. , De Kok Hermine E. , Roels J. A. 
Published: December 2004

AbstractSaccharomyces cerevisiae CBS 426 was grown aerobically in continuous culture with a mixture of glucose and ethanol as the carbon source. The flows of biomass, glucose, ethanol, oxygen, and carbon dioxide were measured. A model for growth with two substrates was derived. Application of this model to the above‐mentioned system yielded values for YATP and P/O. The joint confidence regions for these parameters were calculated. The relevance to industrial production of bakers' yeast is discussed.
Preparation and characterization of enzymes immobilized by graft copolymerization to different polysaccharides
Authors: D'Angiuro L. , Cremonesi P. , Mazzola G. , Focher B. , Vecchio G. 
Published: December 2004

AbstractA method of enzyme immobilization by graft copolymerization on polysaccharides is reported. Glycidylmethacrylate was used as a vinylating reagent and the reaction product with enzymes (HRP, GOD, Am, ChT) was copolymerized with different matrices (cellulose, Sepharose, Sephadex, Starch). Various factors affect the final activity of copolymers; these include the redox system, the type of support, and the quantity and type of vinyl monomer added. Using a fixed quantity of enzyme and support (3 mg enzyme, 100 mg support), the coupling efficiency varied from 2 to 50%. The most important characteristics in these immobilized systems were tested (stability in continuous washing, kinetic characteristics, storage, thermal, and lyophilization stability). Immobilized‐enzyme graft copolymers have very similar kinetic behavior to that of the free enzyme. Diffusion is not seriously limited, as shown by kinetic parameters and energy activation values, and this indicates that the immobilization reaction does not alter the enzymatic activity.
Kinetic studies of cellodextrins hydrolyses by exocellulase from Trichoderma reesei
Authors: Hsu Teh‐An , Gong Cheng‐Shung , Tsao George T. 
Published: December 2004

AbstractThe kinetics of the hydrolyses of cellotriose and of cellotetraose by cellobiohydrolase were studied using a convenient integral technique. Reaction mechanisms and mathematical models were postulated to describe the reactions. The end‐products of the reaction were found to be inhibitory toward hydrolysis in a competitive mode. Hydrolysis of cellotetraose produces cellobiose and hydrolysis of cellotriose produces cellobiose and glucose. Both sugars inhibit the enzyme with cellobiose being a stronger inhibitor.
Concentration of proteins by foaming
Authors: Lalchev Zdr. , Exerowa D. 
Published: December 2004

AbstractFactors influencing foam concentration of proteins are studied. Projecting practical application of the results, the possibilities for obtaining good enrichment ratio are studied. The dependencies of enrichment ratio and albumin concentration in the foam on the initial solution concentration and expansion factor are investigated. Using a method of application of pressure difference in the Plateau‐Gibbs borders of the foam, stabilized by albumin and lysozyme, comparatively high enrichment ratio of the proteins is obtained. The method is applicable for any protein foams and is more effective for more stable foams. The enrichment ratio of albumin significantly depends on the parameters and properties of the foam (dispersion, expansion factor, stability, etc). and also on the initial concentration of the solution. The protein concentration in the foam and the foam dispersion depend in a different way on the initial concentration by the creation of pressure difference in the foam and the Rf/C0 dependence shows a maximum. The latter indicates the existence of an optimum of the initial protein concentration with respect to the efficiency of the foam concentration and the foam separation of proteins from solutions.
Self‐cleaning membranes for ultrafiltration
Authors: Velicangil O. , Howell J. A. 
Published: December 2004

AbstractIn order to reduce the severe flux losses encountered during ultrafiltration of protein solutions, proteases were immobilized on Ultrafiltration membranes to hydrolyze the deposited solute molecules. Over a standard 22 hr run 25 to 78% improvement in cumulative permeate yield was obtained when processing 0.5% albumin or hemoglobin. It was also demonstrated that the flux enhancements were due to the biochemical action of the absorbed protease and not to its physical effect as a prefilter coat. with the aid of a model retardation of gel formation mechanism was demonstrated. Economics of the system were shown to be favorable, improving the rate of return on capital investment up to 50% by reduction of the total membrane area of the plant.
Continuous cell propagation using low‐charge microcarriers
Authors: Crespi Charles L. , Thilly William G. 
Published: December 2004

AbstractMicrocarrier cell culture technology has been extended by the finding that two mammalian epithelial cell lines can be continuously subcultured by simple bead‐to‐bead transfer in normal medium in which calcium concentrations have been reduced. Data are reported which show that the hamster ovary line CHO‐Kl and the monkey kidney line LLC‐MK2 can be subcultured simply by adding fresh microcarriers to the stirred suspension culture. Thirteen generations of continuous exponential growth are demonstrated with two such subcultures for the CHO‐Kl cells and with four such subcultures for the LLC‐MK2 cells. Cell generation times were unchanged by this subculturing approach compared to standard subculturing procedure using trypsin to remove cells from surfaces. We have applied this technique to the production of vesicular stomatitis virus (VSV) from CHO‐Kl cells. Viral yields were comparable (less than twofold difference) in microcarrier cultures which were subcultured via bead‐to‐bead transfer or by the standard means of removing cells from microcarriers with trypsin.
Enhancement of oxygen absorption by magnetite‐containing beads of immobilized glucose oxidase
Authors: Sada Eizo , Katoh Shigeo , Terashima Masaaki 
Published: December 2004

AbstractRates of oxygen absorption into glucose solutions were measured using an immobilized‐enzyme reactor, in which magnetite‐containing beads of immobilized glucose oxidase were moved by a revolving magnetic field to reduce the mass transfer resistances at the gas–liquid interface and around the bead. Data were also obtained for oxygen absorption into glucose solutions containing soluble or immobilized glucose oxidase (without magnetite), as well as for physical absorption of oxygen. The rates of physical absorption for the runs with the magnetite‐containing beads increased because of mechanical stirring caused by spinning of the beads at the gas‐liquid interface. In this case the experimental enhancement factors were found to be larger than those predicted on the basis of the film theory for gas absorption with a pseudo‐first order reaction.
Application of the macroscopic electric charge balance in fermentation modeling
Authors: Heijnen J. J. 
Published: December 2004

AbstractThis article treats the application of the macroscopic electric charge balance in fermentation modeling. From the presented calculations it follows that the definition formula of the so‐called degree of reduction is changed due to the ionic character of the fermentation reactants. It is also shown that the macroscopic electric charge balance, together with the ionic equilibria between fermentation reactants, leads to an expression for the calculation of the pH during fermentation. Finally it is concluded that one should be very careful in the estimation of biomass production from the acid or base feed rates which are necessary for pH control.
Mechanism of inhibition caused by long‐chain fatty acids in anaerobic digestion process
Authors: Hanaki Keisuke , Matsuo Tomonori , Nagase Michihiko 
Published: December 2004

AbstractThe inhibitory effect of long‐chain fatty acids on the anaerobic digestion process was examined in batch experiments using synthetic substrates. The addition of long‐chain fatty acids caused the appearance of the appearance of the lag period in the methane production from acetate and in the degradation of both long‐chain fatty acids and n‐butyrate. Methane production from hydrogen proceeded without lag period although its rate was lowered. Fermentation of glucose was not inhibited. Neutral fat in the whole milk was easily hydrolyzed to long‐chain fatty acids, which brought about the inhibition. The addition of calcium chloride reduced the inhibitory effect of long‐chain fatty but it did not do so after the culture had been exposed to long‐chain fatty acids for more than several hours. The addition of calcium carbonate could not reduce the inhibition because of its insolubility.
Comparison of different methods of glucose oxidase immobilization
Authors: Valentová O. , Marek M. , Švec F. , Štamberg J. , Vodrážka Z. 
Published: December 2004

AbstractGlucose oxidase was immobilized by covalent bond to two basic types of sorbents—glycidylmethacrylate copolymers and bead cellulose. These two types of carries were chemically modified, if needed, by the employing various procedures and subsequently used in the immobilization of native and oxidized glucose oxidase. The samples thus obtained were compared with those of immobilized glucose oxidase bound onto some common carriers. Samples which possessed not only a high absolute activity but also adequate mechanical and flow properties were characterized in greater detail with respect to the immobilization efficiency and kinetic properties of bound glucose oxidase.
Kinetics of biomass formation and citric acid production by Aspergillus niger on pilot plant scale
Authors: Roehr Max , Zehentgruber Otto , Kubicek Christian P. 
Published: December 2004

AbstractCitric acid fermentation on pilot plant scale was studied, using two strains of Aspergillus niger of different productivity. Growth and product formation were analyzed from a high number of data points. Several phases could be distinguished which were described by a sequence of logarithmic, cube‐root, and linear equations. Growth and product formation could be related by a modified Luedeking‐Piret equation, taking into consideration a lag time for the organism to shift to shift into the physiological state ready for product formation. The observed differences in productivity of the two strains are reflected by the different non‐growth‐associated terms of the equation. In light of these findings the classical "type II fermentation" is redefined as a mixed type–resembling type I during trophophase and type III during idiophases.
Application of porous teflon tubing method to automatic fed‐batch culture of microorganisms. I. Mass transfer through porous teflon tubing
Authors: Yamané Tsuneo , Matsuda Morio , Sada Eizo 
Published: December 2004

AbstractFor the purpose of a rational design for an automatic feedback control system incorporating a porous Teflon tubing sensor in semibatch culture, steady‐state mass‐transfer characteristics of tubing sensors have been investigated theoretically and experimentally, and also dynamic responses have been studied experimentally. A distributed mathematical model for steady‐state diffusion has been solved numerically and its solution has been shown as useful for the sensor design. The overall mass‐transfer resistance of radial diffusion has been shown to be the sum of external liquid‐film mass‐transfer resistance and membrane diffusion resistance. The steady‐state experiments using ethanol dissolved in water revealed that its transfer into the tubing was controlled by the molecular diffusion within the tubing‐wall membrane. Oxygen transfer from external water into the tubing was shown experimentally to be controlled by the liquid‐film resistance outside the tubing. In general, the radial mass transfer of a substance having a small Henry's constant is controlled by the liquid‐film resistance.The response of the tubing sensor‐detector‐recorder system for the stepwise addition of ethanol into the external water could not be represented by a simple combined system of the first‐order delay with lag time. The responses depend on the characteristics of the tubing as well as flow rate of the carrier gas, etc., but they were quite excellent in all cases (e.g., 90% in 20 s).
Microcalorimetric study of aerobic growth of Escherichia coli in batch culture
Authors: Ishikawa Yasufumi , Nonoyama Yukio , Shoda Makoto 
Published: December 2004

AbstractThermograms of an aerobic batch culture of Escherichia coli K‐12 in synthetic medium were obtained by using a newly designed mecrocalorimeter. The thermograms reflected sharp changes of metabolic activity in glucose‐, nitrogen‐, or oxygen‐limited cultures. The thermo chemical analysis for each culture condition was done using the data of the heat evolved, the head of combustion of cells, and the elementary analysis of the cells. The efficiency of energy conversion determined experimentally revealed nutritional differences.
Hydrocracking of the oils of Botryococcus braunii to transport fuels
Authors: Hillen L. W. , Pollard G. , Wake L. V. , White N. 
Published: December 2004

AbstractHydrocarbon oils of the alga Botryococcus braunii, extracted from a natural “bloom” of the plant, have been hydrocracked to produce a distillate comprising 67% gasoline fraction, 15% aviation turbine fuel fraction, 15% diesel fuel fraction, and 3% residual oil. The distillate was examined by a number of standard petroleum industry test methods. This preliminary investigation indicates that the oils of B. braunii are suitable as a feedstock material for hydrocracking to transport fuels.
Continuous ethanol production and cell growth in an immobilized‐cell bioreactor employing Zymomonas mobilis
Authors: Arcuri E. J. 
Published: December 2004

AbstractEthanol‐producing bioreactors employing cells of Zymomonas mobilis attached to glass‐fiber pads were operated continuously for as long as 28 days. Ethanol production, which is related to bed‐associated biomass levels, was found to occur in three distinct phases: an exponential phase, a linear phase, and a “steady‐state” phase. After prolonged operation, a bacterial floc developed in the reactor. The maximum effluent ethanol concentration and the maximum volumetric productivity were 6.4% and 152 g L−1 h−1, respectively, and both were attained at a liquid residence time of from 10–15 min. Both maxima occurred after the development of the bacterial floc. The flocculant bacterium has been isolated and tentatively identified as a flocculant strain of Z. mobilis.
Effect of nitrogen‐mediated changes in alkalinity on pH control and CO2 supply in intensive microalgal cultures
Authors: Goldman Joel C. , Dennett Mark R. , Riley Carol B. 
Published: December 2004

AbstractThe freshwater alga Scenedesmus obliquus was grown in continuous culture at a fixed dilution rate of 0.5/day, but at varying pH in the range 4.17–10.67. The pH was regulated in the range 4.17–7.67 by continuously bubbling 1% CO2‐enriched air into the cultures and by varying the source of nitrogen (NO, NH, or urea) in the growth medium, which, in turn, led to changes in culture alkalinity. Culture alkalinity and P were the sole determinants of pH. A pH‐stat system, together with NO in the medium, was used to regulate the pH in the range 7.92–10.67. Maximum productivity, which occurred at pH 6.6, was dependent on N source only to the extent that culture alkalinity was a function of nitrogen uptake. The results demonstrate that the choice of N is a critical factor in controlling the pH of large‐scale algal cultures. NH is a poor source of N because it leads to destruction of culture alkalinity and concomitant growth‐inhibiting reductions in pH, whereas NO has an opposite effect, although pH is not so severely affected in this case. Urea is, by far, the most suitable N source for maximizing algal yield when it is supplied in combination with the proper amounts of HCO alkalinity in the growth medium and percent CO2 in the bubbled gas that will lead to an equilibrium pH near the optimum pH.
Kinetic study of sulfide leaching by galvanic interaction between chalcopyrite, pyrite, and sphalerite in the presence of T. ferrooxidans(30°C) and a thermophilic microorganism (55°C)
Authors: Mehta A. P. , Murr L. E. 
Published: December 2004

AbstractA systematic, kinetic study and comparison of the leaching of mixed metal sulfides by galvanic conversion and in the presence of bacteria has been carried out for the first time using both powder (−100 to −400 mesh) and larger (bulk) specimen systems. The rates of dissolution of copper from chalcopyrite and zinc from sphalerite as single, electrically isolated (separate) systems were compared with electrically contacting (galvanically coupled) systems involving CuFeS2/FeS2 and ZnS/FeS2, with and without bacteria and at temperatures of 30 and 55°C. The dissolution of Cu was observed to increase by a factor of 4.6 when the galvanic leaching of CuFeS2/FeS2 was compared to CuFeS2 leaching at 30°C. When bacteria were present, Cu dissolution increased by an additional factor of 2.1 in the CuFeS2/FeS2 system. At 55°C, the corresponding ratios for Cu were 4.3 and 2.7, respectively. The galvanic leaching of Zn in the ZnS/FeS2 system compared to ZnS leaching increased by a factor of 2 at 30°C; in the presence of bacteria the dissolution of Zn from the ZnS/FeS2 system increased by an additional factor of 1.3 at the same temperature. By comparison, the ratio of Cu dissolution from CuFeS2 in acid‐bacterial medium and sterile controls (without bacteria) was 5.5. The corresponding ratio for Zn from ZnS was 2.2 at both 30 and 55°C. The order of reaction was found to be essentially first order for the leaching of powder systems at both 30 and 55°C (with T. Ferrooxidans and thermophilic microorganisms, respectively). The corresponding reaction rate constants were observed to be 12.6 and 22.9 for T. ferrooxidans and the thermophilic microorganisms, respectively. Activation energies for the various systems were also determined.
Activated sludge treatment of synthetic wastewater containing pentachlorophenol
Authors: Edgehill Richard U. , Finn Robert K. 
Published: December 2004

AbstractActivated sludge treatment of a pentachlorophenol (PCP)‐containing synthetic waste was examined. With a waste containing some sugars, and 40–120 mg/L PCP, laboratory activated sludge required about seven days for acclimation. However, the prior addition of a quasipure culture of PCP‐metabolizing Arthrobacter resulted in immediate acclimation. Even with acclimated sludge, however, the system was upset for two days by a simple step change from 40 to 120 mg/L of PCP. The stability of the system to such a shock load was considerably improved when a chemostat culture of the PCP‐metabolizing Arthrobacter was fed slowly into the mixed liquor. Kinetic models were developed to describe the dynamic response of the system in terms of growth parameters, hydraulic detention time, sludge age, and bleed‐in rate from the chemostat.
Application of macroscopic balances to the identification of gross measurement errors
Authors: Wang Nam Sun , Stephanopoulos Gregory 
Published: December 2004

AbstractA systematic method is presented which is capable of both detecting the presence of grossly biased measurement errors and locating the source of these errors in a bioreactor through statistical hypothesis testing. Equality constraints derived from material and energy balances are employed for the detection of data inconsistencies and for the subsequent identification of the suspect measurements by a process of data analysis and rectification. Maximum likelihood techniques are applied to the estimation of the states and parameters of the bioreactor after the suspect measurements have been eliminated. The level of significance is specified by the experimenter while the measurments are assumed to be randomly, normally distributed with zero mean and known variances. Two different approaches of data analysis, batchwise and sequential, that lead to a consistent set of adjustments on the experimental values, are discussed. Several examples based on the fermentation data taken from literature sources are presented to demonstrate the utility of the proposed method, and one set of data is solved numerically to illustrate the computational aspect of the algorithm.
Ethanol fermentation in a yeast immobilized tubular fermentor
Authors: Gencer M. A. , Mutharasan R. 
Published: December 2004

AbstractIn this article, a mathematical model describing the kinetics of ethanol fermentation in a whole cell immobilized tubular fermentor is proposed. Experimental results show reasonable agreement with the proposed model. A procedure for treating the fermentation data for determining the ethanol inhibition constants k1 and k2 is described. The ethanol productivity of the immobilized cell fermentor is compared with those of traditional fermentors. Experimental studies indicate that with Saccharomyces cerevisiae (NRRL Y132) culture, ethanol productivity in the range 21.2–83.7 g ethanol L−1 h−1 at ethanol concentration of 76–60 g/L can be achieved. This is comparable to or higher than those reported in the literature for yeast. The product yield factor of 0.5 g ethanol/g glucose was obtained. The immobilized cell fermentor does not show washout at dilution rates of 7 h−1 and shows good stability over a 650‐h operating period.