bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modeling of bacterial growth; Formulation and evaluation of a structured model
Authors: Esener A. A. , Veerman T. , Roels J. A. , Kossen N. W. F. 
Published: December 2004

AbstractModels which consider changes in the composition of biomass in response to environmental changes are called Structured models. They provide a more comprehensive description of microbial behavior than unstructured models. Compared with the unstructured modeling efforts, very little has so far been done on the theory and practice of structured model building. In most of the works reported so far, no experimental data were provided, and hence no means of testing the proposed models were offered. Others only reported macroscopic response data and not the cellular composition. In an attempt to fill some of the gaps in this field, in this work, first the general formal approach to structured modeling is developed in matrix notation. Then, a simple two‐compartmental model, i.e., a structured model describing the activity of the biomass with two variables, is described. The cell is divided into two fractions, one of which relates to the RNA fraction. The proposed model was then critically evaluated with experimental data, including the RNA data, obtained from fed‐batch and continuous‐culture experiments. The importance of using cellular structure data for model verification, i.e., RNA data in this case, is shown. Shortcomings and capabilities of the developed model are discussed.
Metabolic parameters of the earthworm Eisenia foetida in relation to temperature
Authors: Hartenstein Roy 
Published: December 2004

AbstractComparisons of rate of achieving sexual maturity, cocoon production, and growth rate at six temperatures between 15 and 30°C led to the conclusion that the earthworm Eisenia foetida can be produced optimally over the range 18‐25°C and perhaps maximally at 20°C.
Cell immobilization in k‐carrageenan with tricalcium phosphate
Authors: Wang Henry Y. , Hettwer David J. 
Published: December 2004

AbstractThe objectives of this research were to investigate the growth of immobilized yeast cells in k‐carrageenan gel and study the effect of trapping hydroxyapatite (tricalcium phosphate) crystals into the matrix. Using k‐carrageenan, the final number of cells per milliliter of gel is at least an order of magnitude higher than free cells per milliliter of medium. A “cell retention” theory explaining this cell concentration difference was proposed. Coexistence of yeast cells and an additional agent such as tricalcium phosphate results in sustained viability through internal pH control, increased cell loading, greater settling velocity, and enhanced ethanol production.
Fluidized‐bed fermenters: A steady‐state analysis
Authors: Andrews Graham F. 
Published: December 2004

AbstractA new mathematical model is presented model is presented for use in the design and optimization of fluidized‐bed fermenters. Unlike previous models, the biomass particle size is not a required input parameter, but is predicted as a consequence of the process by which the fermenter reaches a steady state. Both tower fermenters and supported‐film bioreactors are included in the analysis. The differences between them are explained as a consequence of the different effects of added biomass on the particle settling velocity and the tendency of a fluidized bed to stratify. A detailed qualitative treatment of solids mixing allows the model to predict the varying biomass concentration through a tower fermenter and the more constant concentration in the supported film reactor. Other features of this analysis are the inclusion of an axial dispersion term to allow for different liquid mixing conditions, and the introduction of a variable transformation that eliminates the need for a computer solution. A sample design problem is included.
A study of cellobiose fermentation by a Dekkera strain
Authors: Blondin B. , Ratomahenina R. , Arnaud A. , Galzy P. 
Published: December 2004

AbstractThe Dekkera intermedia strain studied has the ability to ferment cellobiose. The ethanol concentration obtained was 75 g/L from 180 g/L cellobiose (80% of theoretical yield). The fermentation of more concentrated solutions of cellobiose did not proceed well.
Kinetics of yeast alcohol dehydrogenase and its coenzyme coimmobilized in a tubular flow reactor
Authors: Mazid M. A. , Laidler K. J. 
Published: December 2004

AbstractYeast alcohol dehydrogenase and nicotinamide adenine dinucleotide (NAD) were coimmobilized, with covalent attachment, to the interior surface of a nylon tube. The NAD was attahed at the N6 group of the adenine moiety; an NAD derivative was prepared and attached to free carboxyl groups at a partially hydrolyzed nylon surface. The enzyme was attached, through glutaraldehyde residues, to free amino groups on the surface. Kinetic studies were carried out in which the reduced NAD was recycled by means of phenazine ethosulfate and 2,6‐dichlorophenol indophenol. The reaction was studied over a range of flow rates and ethanol concentrations. The variation of rate with flow rate suggested that there was little diffusion control with respect to ethanol and that there was no observable inhibition by the reaction products. These conclusions were confirmed by evidence based on dimensionless parameters for the reaction and by direct inhibition experiments. The apparent Michaelis constant was lower than when only the enzyme was immobilized, suggesting that the immobilized enzyme‐coenzyme system is of high efficiency. Overall rates of reaction were lower than when there was saturation with NAD. The tube showed no measurable loss of catalytic activity over a period of one month.
Efficiency of the cyclic batch antibiotic fermentation
Authors: Guthke R. , Knorre W. A. 
Published: December 2004

AbstractFor a simple mathematical model of microbial product formation, the productivities of stationary and nonstationary cultivation methods (chemostat and cyclic batch) are compared. Conditions of superiority of the cyclic batch cultivation are characterized. The model includes substrate inhibition of the product formation and the age‐dependent loss of productivity of the culture.
Foam separation of DNA and proteins from solutions
Authors: Lalchev Z. , Dimitrova L. , Tzvetkova P. , Exerowa D. 
Published: December 2004

AbstractFoam separation on BSA‐DNA (bovine serum albumine/deoxyribonucleic acid) and Lysozyme‐DNA systems is performed. The separation of the total protein from DNA is evaluated for dissociated chromatin solution. Foam separation for the same systems is done also by a new method of creating a pressure gradient in the Plateau‐Gibbs borders in the foam and obtaining a “dry” foam. It is shown that the effectiveness of the foam separation can be improved significantly by the application of the latter method. Some factors (pH, initial concentration of the solution, expansion factor of the foam) influencing the separation of proteins from DNA in the foam and in the residual solution are studied as well.
Recovery of ethanol from fermentation broths using selective sorption–desorption
Authors: Pitt W. W. , Haag G. L. , Lee D. D. 
Published: December 2004

AbstractIndustrialized nations face a critical problem in replacing the sources of liquid fuels that traditionally have been supplied by petroleum. One solution that has gained increasing support in this country is the use of ethanol produced by fermentation of renewable biomass as an extender in, or supplement to, gasoline for transportation fuel. Distillation, the present method of separating ethanol from the fermentation broth, is an energy‐intensive one and frequently uses more energy than is available from the ethanol recovered. There are many investigations under way to find alternative, less energy‐intensive techniques for the ethanol–water separation. The separations method described in this article involves the use of solid materials to preferentially remove ethanol from fermentation broths. Subsequent stripping of the ethanol from the sorbent with a dry gas reduces dramatically the energy required for the separation. Three solid sorbents have been investigated experimentally. Their sorption/desorption characteristics are described, and their incorporation in an ethanol recovery process is evaluated. Three sorbents were investigated: two commercially available divinylbenzene crosslinked polystyrene resins in bead form (one with a nominal surface area of 300 m2/g, the other with 750 m2/g) and an experimental proprietary molecular sieve with hydrophobic properties. Equilibrium adsorption isotherms for two of the sorbents were obtained at ambient temperature (21°C) for ethanol–water solutions containing up to 12 wt. % ethanol. In addition, 40°C isotherms were obtained for the polystyrene sorbents. Although different, the equilibrium isotherms for the sorbents indicated that ethanol could be preferentially sorbed from a dilute solution. Column breakthrough curves indicated very favorable kinetics. Desorption of the ethanol was readily effected with warm (60–80°C), dry nitrogen.
Electrophoretic study of the macromolecular compounds excreted by yeasts: Application to differentiation between strains of the same species
Authors: Bouix M. , Leveau J. Y. 
Published: December 2004

AbstractThe macromolecular compounds excreted during growth by yeasts as exocellular fractions were studied and found to contain a high proportion of carbohydrates. On the basis of the specificity of these fractions, an attempt was made to distinguish between nine strains of a single species of yeast—Saccharomyces cerevisiae. Each strain came from a different source. The electrophoretic patterns of the exocellular fractions tested made it possible to distinguish between the nine strains, on the basis of Lodder's criteria for the morphological and physiological identification of yeasts. We considered that strains giving exocellular fractions distinguishable by electrophoresis belonged to distinct clones. Consequently, this technique enables us to go further than diagnosis of the species.
Growth monitoring and control in complex medium: A case study employing fed‐batch penicillin fermentation and computer‐aided on‐line mass balancing
Authors: Mou Duen‐Gang , Cooney Charles L. 
Published: December 2004

AbstractTo broaden the practicality of on‐line growth monitoring and control, its application in fedbatch penicillin fermentation using high corn steep liquor (CSL) concentration (53 g/L) is demonstrated. By employing a calculation method that considers the vagaries of CSL consumption, overall and instantaneous carbon‐balancing equations are successfully used to calculate, on‐line, the cell concentration and instantaneous specific growth rate in the penicillin production phase. As a consequence, these equations, together with a feedback control strategy, enable the computer control of glucose feed and maintenance of the preselected production‐phase growth rate with error less than 0.002 h−1.
The half‐saturation coefficient for dissolved oxygen: A dynamic method for its determination and its effect on dual species competition
Authors: Hao Oliver J. , Richard Michael G. , Jenkins David , Blanch Harvey W. 
Published: December 2004

AbstractA simple approach was developed to determine the half‐saturation coefficient for dissolved oxygen (KDO) for three bacteria by maintaining a constant oxygen concentration in continuous culture, and employing a dynamic method to obtain the specific growth rate (μ) for each species. Measurement of μ at selected dissolved oxygen concentrations (DO) resulted in a typical Monod curve for a plot of μ vs. DO. Values for KDO and μmax were obtained from the Lineweaver–Burk reciprocal plot. The bacteria studied included representative strains of three microorganisms isolated in pure culture from poorly settling activated sludge: two filamentous microorganisms, Sphaerotilus natans and a second Sphaerotilus sp., and an unidentified floc‐forming microorganism. The KDO values obtained for Sphaerotilus sp., S. natans, and the floc former were 0.014, 0.033, and 0.073 mg/L, respectively. Dual species competition experiments were conducted in continuous culture under low and high DO conditions. Successful growth competition by these microorganisms under DO‐limiting conditions was consistent with experimentally determined KDO values. The finding of lower KDO values for the two Sphaerotilus species, compared to the floc former, confirmed the hypothesis that these filamentous microorganisms can outgrow floc‐forming microorganisms in activated sludge when DO in the aeration basin is low.
Cultivation of E. coli in single‐ and ten‐stage tower–loop reactors
Authors: Adler I. , Schügerl K. 
Published: December 2004

AbstractE. Coli was cultivated in batch and continuous operations in the presence of an antifoam agent in stirred‐tank and in single‐ and ten‐stage airlift tower reactors with an outer loop. The maximum specific growth rate, μm, the substrate yield coefficient, Yx/s, the respiratory quotient, RQ, substrate conversion, Us, the volumetric mass transfer coefficient, KLa, the specific interfacial area, a, and the specific power input, P/VL, were measured and compared. If a medium is used with a concentration of complex substrates (extracts) 2.5 times higher than that of glucose, a spectrum of C sources is available and cell regulation influences reactor performance. Both μm and YX/S, which were evaluated in batch reactors, cannot be used for continuous reactors or, when measured in stirred‐tank reactors, cannot be employed for tower‐loop reactors: μm is higher in the stirred‐tank batch than in the tower‐loop batch reactor, μm and Yx/s are higher in the continuous reactor than in the batch single‐stage tower–loop reactor. The performance of the single‐stage is better than that of the ten‐stage reactor due to the inefficient trays employed. A reduction of the medium recirculation rate reduces OTR, Us, Pr, and YX/S and causes cell sedimentation and flocculation. The volumetric mass transfer coefficient is reduced with increasing cultivation time; the Sauter bubble diameter, ds, remains constant and does not depend on operational conditions. An increase in the medium recirculation rate reduces kLa. The specific power input, P/VL, for the single‐stage tower loop is much lower with the same kLa value than for a stirred tank. The relationship kLa vs. P/VL evaluated for model media in stirred tanks, can also be used for cultivations in these reactors.
Effects of ammonia and phosphate limitation on the activated sludge treatment of calcium‐containing chemical waste
Authors: Salanitro J. P. , Sun P. T. , Thornton J. B. 
Published: December 2004

AbstractLaboratory‐scale biotreaters were used to study the effects of NH3‐N and PO4‐P nutrients on the activated sludge treatment of a chemical waste containing soluble calcium (1300 mg/L). Units receiving high or low levels of NH3‐N and PO4‐P were similar in their ability to remove organic compounds from the waste. Adaptation of sludges to low PO4‐P levels (<0.1 mg/L effluent) resulted in a marked accumulation of CaCO3 in the biosolids, whereas those receiving high PO4‐P (2–4 mg/L effluent) had little CaCO3. Microscopic observations of CaCO3 containing sludges showed substantial amounts of CaCO3 crystals imbedded in the biomass. These flocs also appeared to be enriched with nonfilamentous bacterial species in contrast to flocs devoid of CaCO3 which had a floc structure of filamentous and nonfilamentous organisms. Scanning electron micrographs of flocs grown under low NH3‐N showed a microbial fibrillar network of exocellular material interconnecting cells in the floc matrix. The sludges adapted to low NH3‐N also produced higher amounts of extractable polysaccharide. CaCO3 containing biosolids were more dense, larger, and settled better (low SVI, high ISV) than flocs devoid of the precipitates. It is not known from our experiments whether PO4‐P or some inorganic or organic polymer produced by the floc bacteria are involved in inhibiting CaCO3 precipitation in the activated sludge treatment of calcium‐containing wastes.
Preparation and properties of trypsin chemically attached to EEDQ activated styrene–methacrylic acid copolymers
Authors: Telefoncu A. 
Published: December 2004

AbstractStyrene–methacrylic acid copolymers of varying combinations crosslinked with p‐DVB (1–2%) and porous structure were synthesized to be used as carriers in trypsin immobilization. The styrene–methacrylic acid copolymers containing free carboxy groups were activated by conversion into the mixed carbonic anhydride with N‐ethoxycarbonyl‐2‐ethoxy‐1,2‐dihydroquinoline (EEDQ) at pH 4.0. The degree of activation of copolymers were determined from the amount of p‐aminobenzoic acid each could bind. The activated copolymers were incubated with trypsin in phosphate buffer (pH 8.0) at 4°C for 24 h. The optimum conditions for enzymatic activity measurements determined and the activity tests were carried out in 1.5 × 10−2M CaCl2 solution (pH 8.0) at 0.05 ionic strength with a pH‐stat instrument. The dependence of the activity of styrene–methacrylic acid (SMA)/trypsin derivatives to pH was investigated and it was observed that the optimum pH of the immobilized trypsin derivatives moved to the basic region compared to the native trypsin. It was found that as the ionic strength increased, the shift in the optimum pH decreased and the activity increased. The Michaelis constants for the SMA–trypsin derivatives were determined with aid of Lineweaver–Burk diagrams. The thermal, storage, and operational stabilities of SMA–trypsin derivatives were assessed. It was found that the above stabilities for all the immobilized trypsin derivatives were better than that for the native trypsin.
Fermentation monitoring by polymeric‐resin‐based microbiol assay
Authors: Seaton Jay J. , Wang Henry Y. 
Published: December 2004

AbstractA polymeric‐resin‐based microbiological assay is shown to yield results consistent with classical inhibition zone theory. This novel assay is applicable to cycloheximide, an antifungal antibiotic, at concentrations below 1.0 μg/mL and up to 800 μg/mL. Addition of ethanol to the cut‐out wells of the assay plate helps to release the antibiotic and drastically increases the inhibition zone size. The antibiotic concentrations of both two component and multicomponent systems can be determined using this method. The use of polymeric‐resin beads to monitor antibiotic concentrations is shown to be an effective technique for fermentation monitoring.
Particle size reduction by breakage in biological wastewater treatment
Authors: Glasgow Larry A. , Pollock Ronald J. , Barkley William A. 
Published: December 2004

AbstractFloc breakup in biological wastewater treatment occurs in response to hydrodynamic stresses imposed by aeration, recirculation, and mixing. This size reduction is of particular concern because it leads to solids carry‐over and adversely affects process controllability. A laboratory study of floc size reduction has shown how the hydrodynamic environment causes breakup and the extent to which it proceeds at particular levels of dissipation. The structure of jet flows was found to be well‐suited for the reduction of floc size.
Heat and mass transfer effects in static solid–substrate fermentations: Design of fermentation chambers
Authors: Rathbun B. L. , Shuler M. L. 
Published: December 2004

AbstractAn experimental device was constructed to allow nearly simultaneous measurements to be made on temperature and gas composition at different depths in a solid–substrate fermentation bed. The time‐dependent values of temperature, mol % O2 and mol % CO2 were measured at five positions in beds 6.35 cm (2.5 in.) deep. With a tempeh fermentation (Rhiopus oligosporus growing on soybeans) the temperature gradient could be as steep as 3°C/cm during active mold growth and concentration of CO2 could reach 21 vol. % in the bottom layer.
Confining mycelial growth to porous microbeads: A novel technique to alter the morphology of non‐newtonian mycelial cultures
Authors: Gbewonyo Kodzo , Wang Daniel I. C. 
Published: December 2004

AbstractIn an effort to alter the filamentous morphology of Penicillium chrysogenum cells, a technique was developed to confine the growth of the mycelia to porous celite beads. The pore matrix of these beads was found to be very effective for entrapping mycelial cells and spores. The entrapped spores were used to initiate the fermentations in shake flask cultures. Significant increases in final cell densities were obtained in the confined cell cultures reaching up to 60 g/L cells. This is nearly double the cell concentration attainable in free cell cultures grown in the absence of beads. Cell loadings up to 0.55 g cells per bead were obtained in the confined cell cultures. In the later stages of the fermentations, the specific oxygen uptake rates in the confined cell cultures were found to decrease with respect to free cell cultures.
A simple, sensitive, and accurate alcohol electrode
Authors: Verduyn C. , Van Dijken J. P. , Scheffers W. A. 
Published: December 2004

AbstractThe construction and performance of an enzyme electrode is described which specifically detects lower primary aliphatic alcohols in aqueous solutions. The electrode consists of a commercial Clark‐type oxygen electrode on which alcohol oxidase (E.C. 1.1.3.13) and catalase were immobilized. The decrease in electrode current is linearly proportional to ethanol concentrations between 1 and 25 ppm. The response of the electrode remains constant during 400 assays over a period of two weeks. The response time is between 1 and 25 min. Assembly of the electrode takes less than 1 h.
Hydrodynamics, mass transfer, and yeast culture performance of a column bioreactor with ejector
Authors: Prokop A. , Janík P. , Sobotka M. , Krumphanzl V. 
Published: December 2004

AbstractA bubble column fitted with an ejector has been tested for its physical and biological performance. The axial diffusion coefficient of the liquid phase in the presence of electrolytes and ethanol was measured by a stimulus‐response technique with subsequent evaluation by means of a diffusion model. In contrast to ordinary bubble columns, the coefficient of axial mixing is inversely dependent on the superficial air velocity. The liquid velocity acts in an opposite direction to the backmixing flow in the column. The measurement of volumetric oxygen transfer coefficient in the presence of electrolytes and ethanol was performed using a dynamic gassing‐in method adapted for a column. The data were correlated with the superficial air and liquid velocities, total power input, and power for aeration and mixing; the economy coefficient of oxygen transfer was used for finding an optimum ratio of power for aeration and pumping. Growth experiments with Candida utilis on ethanol confirmed some of the above results. Biomass productivity of 2.5 g L−1 h−1 testifies about a good transfer capability of the column. Columns fitted with pneumatic and/or hydraulic energy input may be promising for aerobic fermentations considering their mass transfer and mixing characteristics.