bluuebunny/crossref_metadata_2025_split huggingface dataset:
Startup of anaerobic downflow stationary fixed film (DSFF) reactors
Authors: Kennedy K. J. , Droste R. L. 
Published: December 2004

AbstractOne of the serious problems limiting the application of full‐scale anaerobic fixed film processes is reactor startup. To better understand startup, studies with downflow stationary fixed film (DSFF) reactors were conducted to characterize the effects of influent concentration, support material, and surface‐to‐volume ratio on biofilm development and overall reactor performance. Materials with roughened surfaces gave the best startup performance and as expected increased surface area in the reactors led to more rapid increases in loading rates and higher ultimate loadings. Soluble influent COD concentrations between 5 × 103 and 2 × 104 mg/L influenced the rate of biofilm development. Lower COD concentrations resulted in faster development of the biofilm, even though ultimate loadings were not necessarily achieved as rapidly as in reactors fed higher strength wastes. No decrease in specific activity of the biofilms in each reactor was observed as the thickness of the biofilms increased to their maximum value at the ultimate loadings. The operation of reactors fed lower strength wastes was more stable than reactors receiving higher strength feeds at comparable loadings. Biofilm yield and activity, COD removals, suspended growth and activity, and other system parameters are discussed.
Noninferior periodic operation of the biological reactor
Authors: Matsubara Masakazu , Hasegawa Sachiyuki , Shimizu Kazuyuki 
Published: December 2004

AbstractThe optimal periodic operation of the biological reactor was studied from the standpoint of the two‐objective programming problem. The noninferior set with respect to the cell productivity and the conversion of the substrate into the biomass was determined by use of the optimization technique due to Miele. It was shown that the noninferior set was composed in general of the repeated batch branch and the repeated fed‐batch branch, which occupy the high‐productivity portion and the high‐conversion portion of the noninferior set, respectively. However, the latter branch disappears in the case of growth kinetics with no substrate inhibition. In addition, the extreme points of the noninferior set yielding the maximal productivity and the maximal conversion represent such operations that are equivalent to the steady‐state operation (chemostat culture) and the batch operation, respectively.
Gas chromatography and gateway sensors for on‐line state estimation of complex fermentations (butanol‐acetone fermentation)
Authors: McLaughlin Joseph K. , Meyer Charles L. , Papoutsakis Eleftherios T. 
Published: December 2004

AbstractA fermentation system has been designed to demonstrate the use of gas chromatography (GC) for on‐line monitoring of the butanol‐acetone and other complex saccharolytic fermentations. Tangential flow ultrafiltration was used to sterilely and continuously obtain a cell‐free filtrate from the fermentation broth for on‐line GC analysis of butanol, butyrate, acetate, acetone, ethanol, and acetoin. The liquid injection system consists of a phosphoric acid contactor, a slider‐type injection valve, and a heater to address the difficulties (ghosting) encountered in the analysis of carboxylic acids. The fermentation headspace gas was also analyzed by on‐line GC for nitrogen and carbon dioxide, while hydrogen was measured by difference. Raw chromatographic data were analyzed by a chromatography data system. Both raw and processed data were transmitted to a VAX 11/750 computer for further processing (using the fermentation equation) and archiving. The fermentation equation, which has recently been derived and tested on completed fermentation data, was also found to be valid during transient fermentations and thus useful as a gateway sensor for calculating various fermentation parameters on‐line. Such parameters include glucose concentration and gas composition, as well as a number of unobservable parameters (such as YATP, excess ATP, and NAD reduced by FdH2), which characterize the state of the fermentation.
Ethanol fermentation of raw cassava starch with Rhizopus koji in a gas circulation type fermentor
Authors: Fujio Yusaku , Ogata Masafumi , Ueda Seinosuke 
Published: December 2004

AbstractStudies have been conducted in a gas circulation type fermentor in order to characterize the ethanol fermentation of uncooked cassava starch with Rhizopus koji. Results showed that ethanol concentration reached 13‐14% (v/v) in 4‐day broth, and the maximum productivity of ethanol was 2.3 g ethanol/L broth h. This productivity was about 50% compared to the productivity of a glucose‐yeast system. Ethanol yield reached 83.5‐72.3% of the theoretical yield for the cassava starch used. The fermentor used in the present work has been proven by experiment to be suitable for ethanol fermentation of the broth with solid substrate.
Influence of glucose on the kinetics of maltodextrin hydrolysis using free and immobilized glucoamylase
Authors: Vallat I. , Monsan P. , Riba J. P. 
Published: December 2004

AbstractThe study of the effect of glucose addition to the kinetics of maltodextrin hydrolysis catalyzed with free and immobilized Aspergillus niger glucoamylase does not show any significant glucose inhibitory effect. This result is in contradiction with data previously reported in the literature. On the contrary, a slight glucose‐activating effect was observed. This effect was greater in the case of the immobilized enzyme. The glucose inhibitory effect may thus not be involved in the case of practical saccharification conditions catalyzed with glucoamylase when maltodextrins are used as substrate.
Regeneration of NAD(P)H by immobilized whole cells of Clostridium butyricum under hydrogen high pressure
Authors: Matsunaga Tadashi , Matsunaga Naoki , Nishimura Shigeo 
Published: December 2004

AbstractImmobilized whole cells of Clostridium butyricum reduced both NAD+ and NADP+ in the presence of hydrogen at a pressure of 100 atm. The NAD+ and NADP+ reduction activities were 4.45 and 4.30 U/g dry cells, respectively [U = NAD(P)H regenerated, μ mol/min]. The amount of NADH regenerated by immobilized cells increased with increasing hydrogen pressure above 10 atm. Immobilized cells (6 mg dry cells) of Cl. butyricum completely converted NAD+ (6.4 μmole) to NADH for 5 h, whereas only 60% of NAD+ were reduced by free cells. Immobilized cells retained 89% activity after the 5‐h reactions were repeated 4 times. L‐Alanine was continuously produced at the rate of 12.8 μmol/min g dry cells from hydrogen, ammonium, and pyruvate with immobilized Cl. butyricum‐alanine dehydrogenase.
Kinetic modeling of the enzymatic hydrolysis of pretreated cellulose
Authors: Caminal G. , López‐Santín J. , Solà C. 
Published: December 2004

AbstractThe production of sugars by the enzymatic hydrolysis of cellulose is a two‐step process that includes conversion of the intermediate cellobiose to glucose by β‐glucosidase. The hydrolysis was followed by analyzing the two sugar products (cellobiose and glucose). The enzyme showed maximum activity at pH 4.8. Thermal deactivation was significant at temperatures above 45°C. At 50°C (optimum temperature) thermal deactivation was found to follow first‐order kinetics. Several models were tested by modeling the kinetics of the reaction. Their parameter values were determined by numerical optimization, including temperature dependence. The best fitting model was a competitive product inhibition for the two reactions in the operational range.
Solid‐state ethanol fermentation by means of inert gas circulation
Authors: Sato K. , Nakamura K. , Sato S. 
Published: December 2004

AbstractA new method for solid‐state ethanol fermentation (the SSEF system) was experimented on for the ethanol production from solid starchy materials, where a packedbed‐type fermentor was used. Both cultivation of Aspergillus saitoi and enrichment of a saccharifying enzyme were effective for hydrolysis of the starch. Ethanol production was set in by a form of parallel fermentation using a respiration‐deficient mutant of Saccharomyces cerevisiae. Produced ethanol was simultaneously stripped by circulating inert gas and separated in a condenser. Average ethanol concentration in the condensate was over 200 g/L, and over 90% of produced ethanol was recovered from the packed bed during 15 or 16 days of stripping. The fermentation efficiency was about 80%, which was evaluated much higher than those of conventional solid‐state fermentations. The residue had lesser volume and a higher solids content compared with the distillery wastewaters of conventional liquid‐state fermentations. This means an advantage for the treatment and the effective conversion of the residue into fetilizers or animal feeds.
Fermentation and recovery of the EcoRI restriction enzyme with a genetically modified Escherichia coli strain
Authors: Botterman J. H. , De Buyser D. R. , Spriet J. A. , Zabeau M. , Vansteenkiste G. C. 
Published: December 2004

AbstractThe fermentation and recovery of the EcoRl restriction endonuclease with a genetically modified Escherichia coli strain is investigated. Vast amounts of product could be obtained after cultivation in a 20‐L computer‐coupled pilot fermentor and purification of the recovered wet cells. It was found that in the end the product is at least inhibitory and probably lethal to the cells (the lethality has been proven with genetic experiments) so that optimum yield requires an optimized choice for the time instant of induction. Growth after induction and product formation require substantial amounts of oxygen, which must be supplied if a high population level is to be achieved. pH control may alleviate the burden of high oxygen supply. Quantitative assessment after the different purification stages indicate that approximately 15% active enzyme can be obtained from the total amount produced.
Monitoring of protein product formation during fermentation with fast protein liquid chromatography
Authors: Gustafsson Jan‐Gunnar , Frej Ann‐Kristin , Hedman Per 
Published: December 2004

AbstractA method is described using fast protein liquid chromatography (FPLC) for the monitoring of protein formation during fermentation. The procedure consists of centrifugation to recover the cells, sonication of the cells, centrifugation to remove cell debris, and analysis of supernatant on a column of Mono Q (a strong anion exchanger). Analysis of peak areas provides quantitative determination of product concentration. Maintenance and life of the Mono Q column is discussed. We find that FPLC is a convenient method for measuring products in cell homogenates because it gives rapid, highly resolved separations.
Transient responses of continuously growing yeast cultures to dilution rate shifts: A sensitive means to analyze biology and the performance of equipment
Authors: Kätterer L. , Allemann H. , Käppeli O. , Fiechter A. 
Published: December 2004

AbstractTransient responses of continuously growing yeast cultures to step changes in dilution rate were influenced by (1) the preshift conditions of the culture, (2) the magnitude of the dilution rate increase, (3) the organism involved, and (4) the type of bioreactor used. The sensitivity of transient responses to seemingly minor differences in the design of experiments indicated that this type of investigation may be a means to analyze kinetics of microbial cultures as well as the effectiveness of bioreactors.
Models for high cell density bioreactors must consider biomass volume fraction: Cell recycle example
Authors: Monbouquette Harold G. 
Published: December 2004

AbstractIntrinsic models, which take into account biomass volume fraction, must be formulated for adequate simulation of high‐biomass‐density fermentations with cell recycle. Through comparison of corresponding intrinsic and non‐intrinsic models in dimensionless form, constraints for non‐intrinsic model usage in terms of biokinetic and fermenter operating parameters can be identified a priori. Analysis of a simple product‐inhibition model indicates that the non‐intrinsic approach is suitable only when the attainable biomass volume fraction in the fermentation broth is less than about 0.10. Inappropriate application of a non‐intrinsic model can lead to gross errors in calculated substrate and product concentrations, substrate conversion, and volumetric productivity.
Microencapsulation of mammalian cells in a water‐insoluble polyacrylate by coextrustion and interfacial precipitation
Authors: Sefton Michael V. , Dawson Roger M. , Broughton Richard L. , Blysniuk John , Sugamori Mark E. 
Published: December 2004

AbstractA process for the microencapsulation of mammalian cells in a commercially available water‐insoluble polyacrylate (EUDRAGIT RL) is described, and the effects of process parameters are outlined The polymer dissolved in diethyl phthalate was pumped along the annulus formed from two concentric needles, while the cell suspension was pumped inside the inner needle Droplets of polymer solution containing cells were blown off the end of the needles by a coaxial air stream. The droplets fell into a corn oil–mineral oil curing bath, in which the solvent was removed from the nascent capsule causing the polymer to precipitate around the cell suspension core. Capsules were washed free of oils and solvent in a fractionated plasma that allowed for quantitative transfer of capsules from the oil phase to an aqueous medium. By appropriate adjustment of the coaxial air flow rate, capsule size could be varied from 250–1000 μm, although the most convenient size was found to be 400–700 μm. Adding Ficoll 400 to the cell suspension to match the density of the suspension to the polymer solution resulted in capsules with a well‐centered core but did not affect capsule strength. It appeared that increasing the polymer solution concentration or the polymer to the cell flow rate ratio resulted in an increased capsule strength, although differences in capsule size made unequivocal conclusions difficult. These capsules are of potential use as an artificial pancreas for the treatment of diabetes (with pancreatic islets) or for large‐scale tissue culture and the production of bioactive products (e.g., with fibroblasts).
Selection of microcarrier diameter for the cultivation of mammalian cells on microcarriers
Authors: Hu W.‐S. , Wang D. I. C. 
Published: December 2004

AbstractThe kinetics of mammalian cell growth in a microcarrier culture are affected by the distribution of cells on microcarriers. It has been shown previously that a critical cell number per microcarrier is required for the growth of FS‐4 cells on microcarriers. It is advantageous to alter the cell distribution on microcarriers to allow for a larger fraction of microcarriers to acquire enough cells to initiate normal growth. This can be achieved by selecting the diameter of the microcarriers employed. It has also been shown previously that the critical cell number could be reduced by choosing a better culture medium to support low density growth. However, even if all cells inoculated into a culture are capable of growing to confluence, it is still necessary to select the microcarrier diameter ration ally to improve the growth kinetics. The method of selecting the microcarrier diameter is discussed. By employing a improved medium as well as using microcarriers of selected diameter, the multiplication ratio was in creased to 15‐ to 16‐fold for FS‐4 cells, as opposed to 3‐ to 4‐fold typically obtained in a batch culture.
Dynamics of continuous stirred‐tank biochemical reactor utilizing inhibitory substrate
Authors: Sokół W. 
Published: December 2004

AbstractThe model of a continuous‐stirred tank biochemical reactor was developed in which the instant uptake rate of substrate was used. The solutions of the model found for the oxidation of phenol by Pseudomonas putida fitted the experimental data better than the results obtained from the models cited in the literature. The model enables control of the culture parameters so that the unwanted washout of the biomass from the bioreactor can be avoided. A review of the models cited in the literature is also presented.
Chemical stabilization of glucoamylase from Aspergillus niger against thermal inactivation
Authors: Lenders J.‐P. , Crichton R. R. 
Published: December 2004

AbstractThe applicability of crosslinking an enzyme to an oxidized polysaccharide by reductive alkylation to enhance thermostability has been investigated for glucoamylase from Aspergillus niger. Direct covalent coupling of the enzyme to periodate‐oxidized dextran in the presence of NaBH3CN results in a conjugate which has thermal properties similar to those of the native enzyme. Our working hypothesis postulates that enhancement of thermostability will result from rigidification of the protein's conformation subsequent to the formation of multiple covalent bonds between the protein and the support. On the basis of the known characteristics of glucoamylase from Aspergillus niger, it would seem necessary to introduce additional amino groups in the polypeptide chain of the protein. The incorporation of new amino groups was performed in two phases. First, the glycosidic part of glucoamylase was oxidized by periodate and the resulting aldehyde groups were reductively aminated by a diaminoalkane and NaBH3CIM. Secondly, additional amino groups were introduced on carboxyl functions into the previously aminated glucoamylase by a diaminoalkane and a water‐soluble carbodiimide in the presence of maltose to protect the active site. The final derivative was then coupled to periodate‐oxidized dextran T‐70 in the presence of NaBH3CN. Starting with native glucoamylase, three successive operations give rise to a conjugate which retained 27% of the initial activity when measured with soluble starch and 39% when measured with maltopentaose. Using substrates of various sizes, it was observed that steric hindrance at the active site may result from covalent coupling to dextran T‐70. It was demonstrated in heat inactivation experiments that the thermostability of the conjugate was in all cases superior to that of the native enzymes. Finally, it was observed that the operational stability of the conjugate was at least twice that of native glucoamylase at 70°C on 18% maltodextrin. Additional experiments rule out the possibility that thermosta‐bilization of the complex is due to other reasons than the increase in the amino content of the protein prior to crosslinking. Neither chemical modification, reticulation nor change in the net charge of the protein resulted in a derivative of glucoamylase which presented enhanced thermostability after conjugation. We conclude that for enzymes which have a low content of available amino groups, the thermostabilization method proposed previously by the present authors may still be applicable if additional amino groups are introduced into the protein prior to its crosslinking to an oxidized polysaccharide. This new example reinforces the generality of this method of stabilization.
Simple nonsingular control approach to fed‐batch fermentation optimization
Authors: Modak J. M. , Lim H. C. 
Published: December 2004

AbstractDetermination of the optimal feed rate for fed‐batch fermentation is normally a problem in singular control with a state inequality constraint and as such is, in general, difficult to solve, especially for those described by a large number of dynamic mass balance equations. In this article we use a new set of state variables and the culture volume as the control variable. In this way the problem is converted to one of nonsingular control with the magnitude and rate constraints on the manipulated variable and can be numerically solved by a gradient‐based technique, thus avoiding the difficulty associated with singular control problems. Examples are given to illustrate the method.
A novel carbonochloridate for activation of supports containing hydroxyl groups
Authors: Büttner W. , Becker M. , Rupprich Ch. , Boeden H.‐F. , Henklein P. , Loth F. , Dautzenberg H. 
Published: December 2004

AbstractThe conditions for the introduction of active carbonate groups into supports containing hydroxyl groups by reaction with 5‐norbornene‐2.3‐dicarboximido carbonochloridate are described. Up to 1.5 mmol carbonate groups/g dry Sepharose 4B could be bound. In the case of glycine the reaction of the activated supports with the amino groups takes place with a 10‐fold higher rate than the hydrolysis of the carbonate groups, and high coupling yields can be reached. It is shown that the activated supports are well suitable for the preparation of carriers for affinity chromatography or the immobilization of enzymes.
Anoxic–oxic activated‐sludge of cyanides and phenols
Authors: Richards Deanna J. , Shieh Wen K. 
Published: December 2004

AbstractThe anoxic–oxic activated‐sludge process has been evaluated in a laboratory investigation as a means for effective treatment of cyanide‐laden wastewaters, with phenols used as the organic carbon sources for denitrification reactions. The performance of the process was evaluated at different levels of feed cyanide concentration and mean cell residence time (MCRT). The results obtained indicate that the phenolic compounds used can be effectively used as the organic carbon sources to promote denitrification reactions. The effects of cyanide inhibition on overall TOC removal can be alleviated at longer MCRTs. Between 1.2 and 2.2 g TOC can be utilized per gram NO2 + NO3− ‐N removed in the anoxic chamber depending on the prevailing MCRT. Microbial oxidation of cyanide and thiocyanate which yields ammonia is the main mechanism responsible for the removal of cyanide and thiocyanate observed in the anoxic–oxic activated‐sludge process. Excellent removal efficiencies have been observed with feed concentrations up to 60 mg CN−/L and 100 mg SCN−/L Frequent exposure of autotrophic and aerobic cyanideutilizing microbes does not impede their activities in the oxic environment. Good nitrification and denitrification efficiencies are attainable in the anoxic–oxic activated‐sludge process in the presence of high feed cyanide and thiocyanate concentrations, provided that MCRT is maintained at a desirable level. As a result, the microbial degradation of cyanide and thiocyanate in conjunction with nitrification and denitrification to produce innocuous nitrogen gas is feasible in the anoxic–oxic activated‐sludge process.
A novel structured kinetic modeling approach for the analysis of plasmid instability in recombinant bacterial cultures
Authors: Bentley William E. , Kompala Dhinakar S. 
Published: December 2004

AbstractThe instantaneous specific growth rate of a recombinant bacterial culture is directly calculated using a simple structured kinetic modeling approach. Foreign plasmid replication and foreign protein expression represent metabolic burdens to the host cell. The individual effects of these plasmid‐mediated activities on the growth rate of plasmid‐bearing cells are estimated separately. The dynamic and steady state simulations of the model equations show remarkable agreement with widely observed experimental trends in plasmid copy number and foreign protein content. The model provides an important tool for understanding and controlling plasmid instability in recombinant bacterial fermentations. The modeling framework employed here is suitable for studying the metabolism and growth of a variety of microbial cultures.