bluuebunny/crossref_metadata_2025_split huggingface dataset:
Removal of thorium from simulated acid process streams by fungal biomass
Authors: Gadd G. M. , White C. 
Published: December 2004

AbstractBiomass from several fungal species removed thorium from solution in 1M HNO3, pH 0–1. Thorium uptake was saturable with increasing thorium concentration, although the equilibria did not correspond to a simple ad sorption isotherm. Thorium uptake was altered by the biomass concentration, the uptake per unit biomass being reduced at high biomass concentrations. The presence of Al3+ and Fe3+ only slightly inhibited uptake of thorium while Ca2+, Mg2+, and Na+ had no effect. Thus fungal biomass appears capable of removing thorium from solution under chemical conditions existing in acid waste liquors. Thorium uptake was increased by pretreatment using detergent and also, in the case of filamentous fungi, varied with the culture conditions, which implies that the thorium uptake characteristics of fungal biomass are able to be manipulated by these or similar means for optimum performance.
Immobilization of glucose oxidase with Bombyx mori silk fibroin by only stretching treatment and its application to glucose sensor
Authors: Demura Makoto , Asakura Tetsuo 
Published: December 2004

AbstractGlucose oxidase (GOD) was immobilized in Bombyx mori silk fibroin membrane by only physical treatment, i.e., stretching without any chemical reagents. This is due to the structural transition of the silk fibroin membrane from random coil to antiparallel β‐sheet (Silk II) induced by the stretching treatment. Permeability coefficients of glucose and oxygen through the fibroin membrane were determined; the permeability of glucose decreased with increasing degree of stretching. The immobilized enzyme activity was characterized with apparent Michaelis constant K and maximal activity Vm. Optimum pH of the activity of the immobilized enzyme was shifted to the value around neutrality, and the activity was maintained to the higher values on both sides of the optimum pH compared with the case of free enzymes. Thermal stability was scarcely lost even at 50°C, although the free enzyme lost about 70% of the original activity. Thus, the stabilities of the enzyme vs. pH and heat were much improved by the immobilization with silk. Glucose sensor prepared with this GOD‐immobilized fibroin membrane was developed; the capabilities such as the response time, calibration curve, and repeating usage were determined.
Periodic operation of a continuous culture of Baker's yeast
Authors: Abulesz E‐M. , Lyberatos G. 
Published: December 2004

AbstractThe possibility of enhancing the biomass productivity of a continuous culture of Saccharomyces cerevisiae growing on a glucose‐limited medium is addressed. An unstructured Monod‐type model is first identified using steady‐state data. The culture is subjected to step changes in dilution rate, and it is seen that the Monod model is unable to predict even qualitatively the dynamic response of the culture. Incorporation of a time delay allows significant improvement in the transient fit. It is found that the culture has a time lag of about 3 h in adapting its growth rate. Cycling the dilution rate with a period of 3 h leads to substantial improvement in the average biomass productivity.
Study of gaseous substrate fermentations: Carbon monoxide conversion to acetate. 1. Batch culture
Authors: Vega J. L. , Clausen E. C. , Gaddy J. L. 
Published: December 2004

AbstractBiological processes may be used to convert gas phase substrates, such as H2S, CH4, CO, H2, and CO2, to useful products. Utilization of these substrates is often a mass transfer limited process, first requiring absorption across the gas‐liquid interface and diffusion through the culture medium to the cell surface, prior to reaction. This article presents a method for determining fermentation parameters of a gaseous substrate in convenient batch vessels using a modified Monod model. The procedure is illustrated with experimental data for the conversion of carbon monoxide to acetate by the strict anaerobe Peptostreptococcus productus.
Activity and flexibility of alcohol dehydrogenase in organic solvents
Authors: Guinn R. Mark , Skerker Paul S. , Kavanaugh Pascale , Clark Douglas S. 
Published: December 2004

AbstractThe oxidation of cinnamyl alcohol to cinnamaldehyde by horse liver alcohol dehydrogenase (LADH) was carried out in nearly anhydrous organic solvents and in solvents containing from 0.1 to 10% added water. In nearly anhydrous solvents containing less than 0.02% water, the oxidation rate increased as the water solubility in the solvent decreased, but the reaction did not require active LADH. Moreover, the highest activity in nearly anhydrous heptane was obtained by lyophilizing the enzyme from a solution of pH 2.0, even though LADH exhibits virtually no enzymatic activity in water at this pH. The catalytic activity of LADH was restored and increased dramatically as small amounts of water were added to each solvent. In conjunction with the activity measurements, electron paramagnetic resonance (EPR) spectroscopy and two active‐site directed spin labels were used to examine solvent‐dependent structural features of LADH. The EPR spectra indicated that LADH became more rigid as the dielectric constant of the solvent decreased. The degree of rigidity also depended on the pH from which the enzyme was lyophilized, indicating that the ionization state of the enzyme can have an important influence on its dynamics in organic solvents. Finally, adding 1% water to organic solvents had no apparent effect on the enzyme's conformation or flexibility near the spin label, even though enzyme activity was an order of magnitude higher when 1% water was present.
Influence of plasmid origin and promoter strength in fermentations of recombinant yeast
Authors: Da Silva Nancy Anderson , Bailey James E. 
Published: December 2004

AbstractThe effects of plasmid promoter strength and origin of replication on cloned gene expression in recombinant Saccharomyces cerevisiae have been studied in batch and continuous culture. The plasmids employed contain the Escherichia coli lacZ gene under the control of yeast promoters regulated by the galactose regulatory circuit. The synthesis of β‐galactosidase was therefore induced by the addition of galactose. The initial induction transients in batch culture were compared for strains containing plasmids with 2μ and ARS1 origins. As expected, cloned gene product synthesis was much lower with the ARS1 plasmid: average β‐galactosidase specific activity was an order of magnitude below that with the 2μ‐based plasmid. This was primarily due to the low plasmid stability of 7.5% when the plasmid origin of replication was the ARS1 element. The influence of plasmid promoter strength was studied using the yeast GAL1, GAL10, and hybrid GAL10‐CYC1 promoters. The rate of increase in β‐galactosidase specific activity after induction in batch culture was 3–5 times higher with the GAL1 promoter. Growth rate under induced conditions, however, was 15% lower than in the absence of lacZ expression for this promoter system. The influence of plasmid promoter strength on induction behavior and cloned gene expression was also studied in continuous fermentations. Higher β‐galactosidase production and lower biomass concentration and plasmid stability were observed for the strain bearing the plasmid with the stronger GAL1 promoter. Despite the decrease in biomass concentration and plasmid stability, overall productivity in continuous culture using the GAL1 promoter was three times that obtained with the GAL10‐CYC1 promoter.
An investigation into the role of initial KLa on the growth and alkaloid accumulation by cultures of Catharanthus roseus
Authors: Leckie F. , Scragg A. H. , Cliffe K. C. 
Published: December 2004

AbstractThe effect of initial KLa on the batch culture of Catharanthus roseus ID1 in a 12.5‐L bioreactor has been examined. Optimum KLa values were found for both growth and alkaloid accumulation. Different sparger designs were used to alter the KLa values. High KLa values caused increased aggregation of the cultures, depressed biomass yields, and altered patterns of alkaloid accumulation.
A kinetic model for methanogenesis from whey permeate in a packed bed immobilized cell bioreactor
Authors: Yang Shang‐Tian , Quo Meining 
Published: December 2004

AbstractThe fermentation kinetics of methane production from whey permeate in a packed bed immobilized cell bioreactor at mesophilic temperatures and pHs around neutral was studied. Propionate and acetate were the only two major organic intermediates found in the methanogenic fermentation of lactose. Based on this finding, a three‐step reaction mechanism was proposed: lactose was first degraded to propionate, acetate, CO2, and H2 by fermentative bacteria; propionate was then converted to acetate by propionate‐degrading bacteria; and finally, CH4 and CO2 were produced from acetate, H2, and CO2 by methanogenic bacteria. The second reaction step was found to be the rate‐limiting step in the overall methanogenic fermentation of lactose. Monod‐type mathematical equations were used to model these three step reactions. The kinetic constants in the models were sequentially determined by fitting the mathematical equations with the experimental data on acetate, propionate, and lactose concentrations. A mixed‐culture fermentation model was also developed. This model simulates the methanogenic fermentation of whey permeate very well.
Minimizing the errors associated with the determination of effective diffusion coefficients when using spherical cell immobilization matrices
Authors: Petersen James N. , Davison Brian H. , Scott Charles D. 
Published: December 2004

AbstractGel materials are often used to entrap biological catalysts. Several experimental methods have been proposed to estimate the diffusion coefficient of important chemical species within these materials. An error analysis for the bead method was performed and, contrary to previously reported results, when proper experimental conditions were employed, the error associated with the bead method was similar to that obtained using the other common methods.
Studies on the optimization of growth and indole alkaloid production by hairy root cultures ofCatharanthus roseus
Authors: Toivonen L. , Ojala M. , Kauppinen V. 
Published: December 2004

AbstractCatharanthus roseushairy root cultures, genetically transformed withAgrobacterium rhizogenes, produce a wide variety of indole alkaloids. The effect of sucrose, phosphate, nitrate, and ammonia concentrations on growth and indole alkaloid production ofC. roseushairy root cultures were studied by using statistical experimental designs and linear regression analysis. Contradictory effects of these nutrients on growth and indole alkaloid production were found. The maximal growth was obtained by having 77. 8 mg NaH2PO4· H2O/L and 1. 311 g KNO3/L in the medium, whereas the specific production of alkaloids was highest at the lowest levels of all the nutrients studied. The maximal dry weight was obtained with high values of sucrose and ammonia, but clear optimum concentrations could not be found. When having enough nutrients to support reasonable growth, it appeared difficult to affect the specific alkaloid production rates considerably. The growth (dry wt.) with the optimized nutrient concentrations in the medium was more than 50% better than in the control medium with about the same alkaloid production.
The production of the enzyme dextransucrase using nonaerated fermentation techniques
Authors: Barker P. E. , Ajongwen N. J. 
Published: December 2004

AbstractHigh yields of the enzyme dextransucrase have been produced repeatedly by fed‐batch fermentation techniques. Activities in excess of 21.9 U/cm3 have been obtained by culturing Leuconostoc mesenteroides NRRL B‐512(F) under nonaerated fed‐batch fermentation conditions. Aerobic fermentations carried out under identical conditions have consistently produced enzyme of less than 17 U/cm3, but with no difference in the final cell concentration in the broth. Different types of yeast extract have been found to have significant effect on the final cell concentration and more especially on the enzyme activity with enzyme yields varying by as much as 50% when different types of yeast extracts were used.
Plasmid presence changes the relative levels of many host cell proteins and ribosome components in recombinant Escherichia coli
Authors: Birnbaum S. , Bailey J. E. 
Published: December 2004

AbstractRelative levels of many individual proteins in Escherichia coli HB101 strains with 0, 37, 56, and 240 plasmids per chromosome were determined by computer image analysis of two‐dimensional gel electrophoresis patterns. The plasmids investigated had very similar sequences except for small domains encoding the represser of plasmid replication. At the intermediate plasmid copy number of 56, levels of several of the TCA cycle enzymes (oxoglutarate dehydrogenase complex, succinate thiokinase, and succinate dehydrogenase) as well as in aspartate transcarbamoylase increased. At a plasmid copy number of 240, higher amounts of PEP carboxylase as well as several of the heat shock proteins were observed. Furthermore, at high plasmid levels, significant decreases occurred in growth rate, pyruvate kinase I, pyruvate dehydrogenase complex, unadenylated glutamine synthetase, aspartate transcarbamoylase as well as in several of the proteins involved in translation. Decreases in ribosome content as well as in the free 30S and 50S ribosomal subunit pool fractions were also observed in separate analyses. These results indicate that recombinant DNA manipulations can cause major alterations in numerous host cell properties which could significantly influence cloned protein production or metabolic engineering endeavors.
Affinity chromatography as a rapid and convenient method for purification of fungal laccases
Authors: Rogalski J. , Wojtas‐Wasilewska M. , Apalovič R. , Leonowicz A. 
Published: December 2004

AbstractA rapid and convenient method for graduation, isolation, and purification of laccase from Trametes versicolor and Fomes fomentarius culture fluids was developed. For purification affinity chromatography on syringyl‐ and vanillyl‐controlled porosity glass (CPG) columns was applied. The purified laccase of F. fomentarius was immobilized on porous glass. Some properties of the immobilized enzyme in comparison to the free one are discussed.
Enzyme thermoinactivation in anhydrous organic solvents
Authors: Volkin David B. , Staubli Andrea , Langer Robert , Klibanov Alexander M. 
Published: December 2004

AbstractThree unrelated enzymes (ribonuclease, chymotrypsin, and lysozyme) display markedly enhanced thermostability in anhydrous organic solvents compared to that in aqueous solution. At 110‐145°C in nonaqueous media all three enzymes inactivate due to heat‐induced protein aggregation, as determined by gel filtration chromatography. Using bovine pancreatic ribonuclease A as a model, it has been established that enzymes are much more thermostable in hydrophobic solvents (shown to be essentially inert with respect to their interaction with the protein) than in hydrophilic ones (shown to strip water from the enzyme). The heat‐induced aggregates of ribonuclease were characterized as both physically associated and chemically crosslinked protein agglomerates, with the latter being in part due to transamidation and intermolecular disulfide interchange reactions. The thermal denaturation of ribonuclease in neat organic solvents has been examined by means of differential scanning calorimetry. In hydrophobic solvents, the enzyme exhibits greatly enhanced thermal denaturation temperatures (Tm values as high as 124°C) compared to aqueous solution. The thermostability of ribonuclease towards heat‐induced denaturation and aggregation decreases as the water content of the protein powder increases. The experimental data obtained suggest that enzymes are extremely thermostable in anhydrous organic solvents due to their conformational rigidity in the dehydrated state and their resistance to nearly all the covalent reactions causing irreversible thermoinactivation of enzymes in aqueous solution.
Enzymatic cellulose hydrolysis in an attrition bioreactor combined with an aqueous two‐phase system
Authors: Tjerneld Folke , Persson Ingrid , Lee James M. 
Published: December 2004

AbstractCellulose was hydrolyzed in the attrition bioreactor (ABR) with enzyme recycling by employing an aqueous two‐phase system (composed of dextran and polyethylene glycol) and an ultrafiltration unit. The ABR combines wet ball milling and enzymatic hydrolysis in one process step. The cellulase enzymes were more stable in the two‐phase system than in the normal buffer solution. With the initial substrate concentration (Solka Floe BW200) of 40 g/L and intermittent addition of cellulose, sugar was semicontinuously produced at dilution rates of 0.06 h−1 and productivities of 2.1 g/L h, which is approximately a 10‐fold increase of the previously reported values performed in a regular stirred reactor with an aqueous two‐phase system. The conversion of the substrate was 86%.
Measuring kLa with randomly pulsed dynamic method
Authors: Gauthier Line , Thibault Jules , LeDuy Anh 
Published: December 2004

AbstractThis reports on the determination of the overall oxygen transfer coefficient in a mechanically agitated vessel using a randomly pulsed dynamic method. This method consists in exciting the system by randomly switching the inlet gas stream with air or nitrogen with an identical volumetric flow rate. A pseudo‐random binary sequence was used. This procedure is routinely used in process control for the identification of system's transfer function. The pulsed dynamic method gives good reliability (as compared with the traditional gassing‐out method) and reproducibility in water. However, further improvement is needed before it can be used to monitor on‐line thekLaduring a fermentation.
Development of biosensors for the simultaneous determination of sucrose and glucose, lactose and glucose, and starch and glucose
Authors: Watanabe Etsuo , Takagi Masatoshi , Takei Satoko , Hoshi Masakazu , Shu‐gui Cao 
Published: December 2004

AbstractSensors for the simultaneous determinations of sucrose and glucose, lactose and glucose, and starch and glucose were prepared by a combination of the enzyme system shown below and an oxygen electrode: magnified image The mechanism for separating the substrates with the proposed sensors is based on the time lag arising from reaction and diffusion. Invertase, β‐galactosidase, amyloglucosidase, mutarotase, and glucose oxidase were covalently immobilized on triacetyl cellulose membranes containing 1,8‐diamino‐4‐aminomethyloctane. A glucose oxidase membrane, mutarotase membrane, three sheets of triacetyl cellulose membranes, and invertase, or β‐galactosidase or amyloglucosidase membrane were placed in that order on the tip of the oxygen electrode. Calibration curves for sucrose, lactose, and starch were linear up to 40 mM, 60–180 mM, and 10%, respectively. The simultaneous determination of sucrose and glucose, lactose and glucose, and starch and glucose was possible when the amount of glucose coexised was in the range of 2–16% sucrose, 2.8–8.3% lactose, or 0.1–1% starch. The relative errors were ±4% for sucrose and ±3% for lactose in 100 assays. The starch sensor was reused only five times. Each enzyme membrane was fairly stable for more than 10 days.
α‐Amylase adsorption on starch crystallites
Authors: Leloup V. M. , Colonna P. , Ring S. G. 
Published: December 2004

AbstractThe goal of this work was to characterize the adsorption of Bacillus subtills α‐amylase onto crystalline starchy materials of the B‐type polymorph. Monodisperse spherulitic particles (R ż6; 5.0 μm), essentially resistant to α‐amylolysis at 25°C were prepared from short amylose chains (DPn ≈ 15). The α‐amylase adsorbed specifically onto the spherulites, and adsorption was found to be a prerequisite step for hydrolysis. Adsorption was inhibited by the presence of maltose and maltotriose in the reaction mixture. Adsorption isotherm of the enzyme on the particles showed a well developed plateau of 1.62 μg/cm2 at 25°C corresponding to a monolayer adsorption process. The binding free energy calculated from the initial slope of the isotherm was ΔG ≈ −20.7 kJ/mol. This is smaller than published values for the binding of α‐amylase to soluble amylosic chains (ΔG < −30 kJ/mol).
Growth and substrate consumption of Nitrobacter agilis cells immobilized in carrageenan: Part 1. Dynamic modeling
Authors: de Gooijer C. D. , Wijffels R. H. , Tramper J. 
Published: December 2004

AbstractThe modeling of the growth of Nitrobacter agilis cell immobilized in κ‐carrageenan is presented. A detailed description is given of the modeling of internal diffusion and growth of cells in the support matrix in addition to external mass transfer resistance. The model predicts the substrate and biomass profiles in the support as well as the macroscopic oxygen consumption rate of the immobilized biocatalyst in time. The model is tested by experiments with continuously operated airlift loop reactors containing cells immobilized in κ‐carrageenan. The model describes experimental data very well. It is clearly shown that external mass transfer may not be neglected. Furthermore, a sensitivity analysis of the parameters at their values during the experiments revealed that apart from the radius of the spheres and the substrate bulk concentration, the external mass transfer resistance coefficient is the most sensitive parameter for our case.
Growth and substrate consumption of Nitrobacter agilis cells immobilized in carrageenan: Part 2. Model evaluation
Authors: Wijffels R. H. , de Gooijer C. D. , Kortekaas S. , Tramper J. 
Published: December 2004

AbstractA dynamic model that predicts substrate and biomass concentration profiles across gel beads and from that the overall substrate consumption rate by the gel beads containing growing cells was evaluated with immobilized Nitrobacter agilis cells in an airlift loop reactor with oxygen as the limiting substrate. The model predictions agreed well with the observed oxygen consumption rates at three different liquid phase oxygen concentrations. Image analysis showed that 90% of the immobilized cells after 42 days of cultivation was situated in the outer shells in a film of 140 μm, while the bead radius was about 1 mm. The maximum biomass concentration in the outmost film of 56 μm was 11 kg · m−3 gel.
Biodegradation of 3,4‐dichloroaniline in a fluidized bed bioreactor and a steady‐state biofilm Kinetic model
Authors: Livingston Andrew Guy 
Published: December 2004

AbstractMixed culture of microorganisms immobilized onto Celite diatomaceous earth particles were used to degrade 3,4‐dichloroaniline (34DCA) in a three‐phase draft tube fluidized bed bioreactor. Biodegradation was confirmed as the dominant removal mechanism by measurements of the concomitant chloride ion evolution. Degradation efficiencies of 95% were obtained at a reactor retention time of 1.25 h. A mathematical model was used to describe the simultaneous diffusion and reaction of 34DCA and oxygen in the biofilms on the particles in the reactor. The parameters describing freely suspended cell growth on 34DCA were obtained in batch experiments. The model was found to describe the system well for three out of four steady states and to predict qualitatively the experimentally observed transition in the biofilm kinetics from 34DCA to oxygen limitation.