bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biological sulfuric acid transformation: Reactor design and process optimization
Authors: Stucki Gerhard , Hanselmann Kurt W. , Hürzeler Richard A. 
Published: December 2004

AbstractAs an alternative to the current disposal technologies for waste sulfuric acid, a new combination of recycling processes was developed. The strong acid (H2SO4) is biologically converted with the weak acid (CH3COOH) into two volatile weak acids (H2S, H2CO3) by sulfate‐reducing bacteria. The transformation is possible without prior neutralization of the sulfuric acid. The microbially mediated transformation can be followed by physiochemical processes for the further conversion of the H2S.The reduction of sulfate to H2S is carried out under carbon‐limited conditions at pH 7.5 to 8.5. A fixed‐bed biofilm column reactor is used in conjunction with a separate gas‐stripping column which was installed in the recycle stream. Sulfate, total sulfide, and the carbon substrate (in most cases acetate) were determined quantitatively. H2S and CO2 are continually removed by stripping with N2. Optimal removal is achieved under pH conditions which are adjusted to values below the pKa‐values of the acids. The H2S concentration in the stripped gas was 2% to 8% (v/v) if H2SO4 and CH3COOH are fed to the recycle stream just before the stripping column.Microbiol conversion rates of 65 g of sulfate reduced per liter of bioreactor volume per day are achieved and bacterial conversion efficiencies for sulfate of more than 95% can be maintained if the concentration of undissociated H2S is kept below 40 to 50 mg/L. Porous glass spheres, lava beads, and polyurethane pellets are useful matrices for the attachment of the bacterial biomass. Theoretical aspects and the dependence of the overall conversion performance on selected process parameters are illustrated in the Appendix to this article. © 1993 John Wiley & Sons, Inc.
Cell Culture conditions determine the enhancement of specific monoclonal antibody productivity of calcium alginate‐entrapped S3H5/γ2bA2 hybridoma cells
Authors: Lee Gyun Min , Chuck Alice S. , Palsson Bernhard O. 
Published: December 2004

AbstractImmobilization offers several intrinsic advantages over free suspension cultures for the production of monoclonal antibodies. An important advantage of immobilization is the improved specific monoclonal antibody (MAb) productivity (qMAb) that can be obtained. However, there are conflicting reports in the literature on the enhancement of the qMAb with immobilization. The discrepancies between these reports can be attributed to the different to either the cultivation methods used for immobilized cell or to difference between the cell lines used in the various studies. We show that these differences may be attributed to the different cultivation methods used for one model hybridoma cell line. S3H5/ϒ2bA2 hybridoma cells entrapped in different sizes of calcium alginate beads were cultivated in both T‐ and spinner flasks in order to determine whether cultivation methods (T‐ and spinner flasks) and bead size influence the qMAb Free‐suspended cell cultures inoculated with cells recovered from alginate beads were also carried out in order to determine whether changes in the qMab of the entrapped cells are reversible.The cultivation methods was found to influence significantly the qMAb of the entrapped cells. When the entrapped cells in 1‐mn diameter beads were cultivated in T‐flasks, the qMAb was not increased by 200% as previously observed in an entrapped cell culture using 1‐mm‐diameter alginate beads in spinner flasks. The qMAb of the entrapped cell was approximately 58% higher than that of the free‐suspended cells in a control experiment. Unlike the cultivation method, the bead size in the range of 1‐ to 3‐mm diameter did not significantly influence the qMAb, regardless of cultivations methods. The changes in qMAb of an entrapped cells were reversible. When the free‐suspended cells recovered from the T‐ and spinner flasks were sub‐cultured in T‐ and spinner flasks enhanced qMAb of the entrapped cells in both cases decreased to the level of the free‐suspended cell in a control experiments. Taken together, these results shows that the method of cultivation of hybridoma cells immobilized in alginate beads determines the extent of enhancement of the qMAb. © 1993 John Wiley & Sons, Inc.
Effect of dilution rate on growth, productivity, cell cycle and size, and shear sensitivity of a hybridoma cell in a continuous culture
Authors: Martens D. E. , de Gooijer C. D. , van der Velden‐de Groot C. A. M. , Beuvery E. C. , Tramper J. 
Published: December 2004

AbstractTo study the effects of the growth rate of the hybridoma cell Mn12 on productivity, cell cycle, cell size, and shear sensitivity, six continuous cultures were run at dilution rate of 0.011, 0.021, 0.023, 0.030, 0.042, and 0.058 h−1. This particular hybridoma cell appeared to be unstable in continuous culture with respect to specific productivity, as a sudden drop occurred after about 30 generations in continuous culture, accompanied by the appearance of two populations with respect to the cytoplasmic lgG content. The specific productivity increased with increasing growth rate. The shear sensitivity of the cell, as measured in a small air‐lift loop reactor, increased with increasing growth rate. The mean relative cell size, as determined with a flow cytometer, increased with increasing growth rates. Furthermore, the fraction of cells in the S phase increased, and the fraction of cells in the G1/G0 phase decreased with increasing growth rates. © 1993 John Wiley & Sons, Inc.
High cell density cultivation of Pseudomonas oleovorans: Growth and production of poly (3‐hydroxyalkanoates) in two‐liquid phase batch and fed‐batch systems
Authors: Preusting Hans , van Houten Renze , Hoefs André , van Langenberghe Eddy Kool , Favre‐Bulle Olivier , Witholt Bernard 
Published: December 2004

AbstractPseudomonas oleovorans is able to accumulate poly(3‐hydroxyalkanoates) (PHAs) under conditions of excess n‐alkanes, which serve as sole energy and carbon source, and limitation of an essential nutrient such as ammonium. In this study we aimed at an efficient production of these PHAs by growing P. oleovorans to high cell densities in fed‐batch cultures.To examine the efficiency of our reactor system, P. oleovorans was first grown in batch cultures using n‐octane as growth substrate and ammonia water for pH regulation to prevent ammonium limiting conditions. When cell growth ceased due to oxygen limiting conditions, a maximum cell density of 27 g ·L−1 dry weight was obtained. When the growth temperature was decreased from the optimal temperature of 30°−18°C, cell growth continued to a final cell density of 35 g · L−1 due to a lower oxygen demand of the cells at this lower incubation temperature.To quantify mass transfer rates in our reactor system, the volumetric oxygen transfer coefficient (kLa) was determined during growth of P. oleovorans on n‐octane. Since the stirrer speed and airflow were increased during growth of the organism, the kLa also increased, reaching a constant value of 0.49 s−1 at maximum airflow and stirrer speed of 2 L · min−1 and 2500 rpm, respectively. This kLa value suggests that oxygen transfer is very efficient in our stirred tank reactor.Using these conditions of high oxygen transfer rates, PHA production by P. oleovorans in fed‐batch cultures was studied. The cells were first grown batchwise to a density of 6 g · L−1, after which a nutrient feed, consisting of (NH4)2SO4 and MgSO4, was started. The limiting nutrient ammonium was added at a constant rate of 0.23 g NH4+ per hour, and when after 38 h the feed was stopped, a biomass concentration of 37.1 g · L−1 was obtained. The Cellular PHA content was 33% (w/w), which is equal to a final PHA yield of 12.1 g · L−1 and an overall PHA productivity of 0.25 g PHA produced per liter medium per hour. © 1993 John Wiley & Sons, Inc.
Metabolic flux distributions in Corynebacterium glutamicum during growth and lysine overproduction
Authors: Vallino Joseph J. , Stephanopoulos Gregory 
Published: December 2004

AbstractThe two main contributions of this are the solidification of Corynebacterium glutamicum biochemistry guided by bioreaction network analysis, and the determination of bansal metabolic flux distributions during growth and lysine synthesis. Employed methodology makes use of stoichiometrically based mass balances to determine flux distributions in the C. glutamicum metabolic network. Presented are a brief description of the methodology, a through literature review of glutamic acid bacteria biochemistry, and specific results obtained through a combination of fermentation studies and analysis‐directed intracellular assays. The latter include the findings of the lack of activity of glyoxylate shunt, and that phosphoenolpyruvate carboxylase (PPC) is the only anaplerotic reaction expressed in C. glutamicum cultivated on glucose minimal media. Network simplifications afforded by the above findings facilitated the determination of metabolic flux distributions under a variety of culture conditions and led to the following conclusions. Both the pentose phosphate pathway and PPC support fluxes during growth and lysine overproduction branch point does not appear to limit lysine synthesis. © 1993 John Wiley & Sons, Inc.
Phenol removal from waste gases with a biological filter by Pseudomonas putida
Authors: Zilli M. , Converti A. , Lodi A. , Borghi M. Del , Ferraiolo G. 
Published: December 2004

AbstractThe purpose of this study is to investigate the feasibility of biologically removing phenol from waste gases by means of a biofilter using a Pseudomonas putida strain. Two series of both batch and continuous tests have been performed in order to ascertain the microbial degradation of phenol. For the preliminary batch tests, carried out in order to test the effective feasibility of the process and to investigate their kinetic behavior, two different microbial cultures belonging to the Pseudomonas genus have been employed, a heterogeneous culture and a pure strain of P. putida. The results of these comparative investigation showed that the pure culture is more efficient than the mixed one, even when the latter has undergone three successive acclimatization tests. The continuous experiments have been conducted during a period of about 1 year in a laboratory‐scale column, packed with a mixture of peat and glass beads, and utilizing the pure culture of P. putida as microflora and varying the inlet phenol concentration from 50 up to 2000 mg m−3. The results obtained show that high degrees of conversion can be obtained (0.93/0.996) operating at a residence time of 54 s. © 1993 John Wiley & Sons, Inc.
Cadmium biosorption by Saccharomyces cerevisiae
Authors: Volesky B. , May H. , Holan Z. R. 
Published: December 2004

AbstractCadmium uptake by nonliving and resting cells of Saccharomyces cerevisiae obtained from aerobic or anaerobic cultures from pure cadmium‐bearing solutions was examined. The highest cadmium uptake exceeding 70 mg Cd/g was observed with aerobic baker's yeast biomass from the exponential growth phase. Nearly linear sorption isotherms featured by higher sorbing resting cells together with metal deposits localized exclusively in vacuoles indicate the possibility of a different metal‐sequestering mechanism when compared to dry nonliving yeasts which did not usually accumulate more than 20 mg Cd/g. The uptake of cadmium was relatively fast, 75% of the sorption completed in less than 5 min. © 1993 Wiley & Sons, Inc.
Factor affecting enzyme characteristics of bilirubin oxidase suspensions in organic solvents
Authors: Skrika‐Alexopoulos Eleftheria , Freedman Robert B. 
Published: December 2004

AbstractThe activity of bilirubin oxidase toward bilirubin was studied in a liquid/solid two‐phase low‐water organic system using a simple spectrophotometric assay to follow the reaction. The enzyme was lyophilized from aqueous solution before being suspended in the organic solvent reaction medium. The activity was significantly influenced by the properties of the aqueous medium from which the enzyme was lyophilized, specifically its pH, and the quantity and nature of the buffering species. Analyses of these effect showed that the role of buffering species in such systems went beyond their effect in fixing the protonation state of the enzyme. The activity was also influenced by the quantity of water added to the organic solvent reaction medium. The reaction was shown to follow Michaelis‐Menten Kinetics, andKmandkcatwere determined. The liquid/solid two‐phase system studied was extensively compared to a previously studied water‐in‐oil microemulsion system © 1993 Wiley & Sons, Inc.
Pulsatile flow filtration of yeast cell debris: Influence of preincubation on performance
Authors: Wu D. , Howell J. A. , Field R. W. 
Published: December 2004

AbstractThe recovery of proteins from yeast cell debris suspension was investigated using a vortex mixing technique based on the combination of oscillatory flow and a baffled flat‐sheet microfiltration system. For this system, increased protein transmission was obtained through the use of low transmembrane pressures and the preincubation of the yeast cell debris feed suspension at 30°C. Furthermore, a plateau in the flux‐time curve was observed. In the absence of baffles and pulsations, preincubation had a little effect. © 1993 Wiley & Sons, Inc.
Influence of mold growth on the pressure drop in aerated solid state fermentors
Authors: Auria Richard , Morales Marcia , Villegas Elba , Revah Sergio 
Published: December 2004

AbstractThe measurement of pressure drop(ΔP) across an aerated fermentation bed is proposed as alternative on‐line sensor for the qualitative and, in some cases, quantitative, macroscopic changes in a static solid state fermentor. An increase in the ΔP is correlated with the evolution of the different phases of Aspergillus niger growth: germination, vegetative growth, limitation, and sporulation, we observed in the microscope. For the case where the support is not modified during the fermentation and the water content remains constant, i.e., a synthetic resin (Amberlite IRA‐900), the gas phase permeability of the bed is directly related to the biomass content. For example, the permeability of the bed is reduced to 5% of the initial value when biomass attains 21 mg dry biomass/g dry support. Biomass was appropriately predicted from the ΔP measurements in an independent test. Experiments with different initial sucrose solution concentrations showed that biomass could not be produced beyond a certain level (21.5 mg dry biomass/g dry support) which suggests steric limitations. For the case of wheat bran and cane bagasse, the increase in ΔP was related qualitatively to the evolution in the growth and the morphology of the mold . © 1993 Wiley & Sons, Inc.
The kinetics of cometabolism
Authors: Criddle Craig S. 
Published: December 2004

AbstractExperimental observations indicate that the rates of cometabolic transformation are linked to the consumption of growth substrate during growth and to the consumption of cell mass and/or energy substrate in the absence of growth substrate. Three previously proposed models (models 1 through 3) describing the kinetics of cometabolism by resting cells are compared, and the interrelationships and underlying assumptions for these models are explored. Models 1 to 3 are shown to converge at high concentrations of the nongrowth substrate. An expression describing nongrowth substrate transformation in the presence of growth substrate is proposed, and this expression is integrated with an expression for cell growth to give a single unstructured model (model 4) that encompasses models 1 to 3 and describes cometabolism by both resting and growing cells. Model 4 couples transformation of nongrowth substrate to consumption of growth substrate and biomass, and predicts that cometabolism will result, and decreased specific growth rates for a cometabolizing population. Competitive inhibition can also be incorporated in the model. Experimental aspects of model calibration and verification are discussed. The need for models that distinguish between the exhaustion of cell activity and cell death is emphasized. © 1993 Wiley & Sons, Inc.
A mathematical model for dynamic simulation of anaerobic digestion of complex substrates: Focusing on ammonia inhibition
Authors: Angelidaki I. , Ellegaard L. , Ahring B. K. 
Published: December 2004

AbstractA mathematical model for anaerobic degradation of complex organic material, such as manure, has been developed. The model includes an enzymatic hydrolytic step and four bacterial steps and involves 12 chemical compounds. The model focuses on ammonia inhibition and includes a detailed description of pH and temperature characteristics in order to accurately simulate free ammonia concentration. Free ammonia and acetate constitute the primary modulating factors in the model. The model has been applied for the simulation of digestion of cattle manure in continuously stirred tank reactors (CSTRs), and results compare favorably with experimental data. © 1993 John Wiley & Sons, Inc.
Measurements of conformational changes during adhesion of lipid and protein (polylysine and S‐layer) surfaces
Authors: Leckband Deborah , Chen You‐Lung , Israelachvili Jacob , Wickman H. Hollis , Fletcher Madilyn , Zimmerman Robert 
Published: December 2004

AbstractThe adhesion forces between various surfaces were measured using the “surface forces apparatus” technique. This technique allows for the thickness of surface layers and the adhesion force between them to be directly measured in controlled vapor or liquid environments. Three types of biological surfaces were prepared by depositing various lipid‐protein monolayers (with thicknesses ranging from 1 to 4 nm) on the inert, molecularly smooth mica surface: (i) hydrophobic lipid monolayers; (ii) amphiphilic polyelectrolyte surfaces of adsorbed polylysine; and (iii) deposited bacterial S‐layer proteins. The adhesion, swelling, and wetting properties of these surfaces was measured as a function of relative humidity and time. Initial adhesion is due mainly to the van der Waals forces arising from nonpolar (hydrophobic) contacts. Following adhesive contact, significant molecular rearrangements can occur which alter their hydrophobic–hydrophilic balance and increase their adhesion with time. Increased adhesion is generally enhanced by (i) increased relative humidity (or degree of hydration); (ii) increased contact time; and (iii) increased rates of separation. The results are likely to be applicable to the adhesion of many other biosurfaces, and show that the hydrophobicity of a lipid or protein surface is not an intrinsic property of that surface but depends on its environment (e.g., on whether it is in aqueous solution or exposed to the atmosphere), and on the relative humidity of the atmosphere. It also depends on whether the surface is in adhesive contact with another surface and—when considering dynamic (nonequilibrium) conditions—on the time and previous history of its interaction with that surface. © 1993 John Wiley & Sons, Inc.
Observations of aerobic, growing escherichia coli metabolism using an on‐line nuclear magnetic resonance spectroscopy system
Authors: Chen Ruizhen , Bailey James E. 
Published: December 2004

AbstractAn experimental system has been constructed which enables on‐line measurements of phosphorus‐31 (31P) nuclear magnetic resonance (NMR) spectra for growing bacterial suspensions under anaerobic or aerobic conditions. A sample stream from a laboratory bioreactor is circulated to the NMR sample chamber in a gas exchange system which permits maintenance of aerobic conditions for high‐cell‐density cultures. 31P NMR spectra with resolution comparable with those obtained traditionally using dense, concentrated, nongrowing cell suspensions can be obtained at cell densities above 25 g/L with acquisition times ranging from 14 to 3 minutes which decline as cell density increases. This system has been employed to characterize the changes in intracellular state of a stationary phase culture which is subjected to a transition from aerobic to anaerobic conditions. Both intracellular NTP level and cytoplasmic pH are substantially lower under anaerobic conditions. Also, the system has been employed to observe the response of a growing culture to external addition of acetate. Cells are able to maintain pH difference across the cytoplasmic membrane at extracellular acetate concentrations of 5 and 10 g/L. However, acetate concentrations of 20 g/L cause collapse of the transmembrane ΔpH and sharp reduction of the growth rate of the culture. The experimental configuration described should also permit NMR observations of many other types of microbial cultures and of other nuclei. © 1993 John Wiley & Sons, Inc.
Analytical effectiveness calculations concerning the degradation of an inhibitive substrate by a steady‐state biofilm
Authors: van Ede C. J. , Bollen A. M. , Beenackers A. A. C. M. 
Published: December 2004

AbstractA reaction engineering model for the degradation of an inhibitory substrate by a steady‐state biofilm is presented. The model describes both the metabolic rate controlling behavior of this substrate in the biofilm and the effect of diffusion limitation caused by an arbitrary substrate on the active biofilm thickness. An analytical expression for the biocatalyst effectiveness factor is presented on the basis of Pirt kinetics for cell maintenance, first order substrate inhibition kinetics, and zero order substrate consumption kinetics. The proposed expression for the biocatalyst effectiveness factor is much more convenient to incorporate into a macroreactor model than the numerical alternatives. Simple criteria are presented to check the applicability of the model in case of true Monod kinetics. The analytical solution is expected to be particularly applicable to processes where a low soluble organic substrate controls the biomass growth, a situation which is often met in wastewater purification processes of industrial importance. The degradation of phenol by Pseudomonas sp. is treated as an example. © 1993 John Wiley & Sons, Inc.
A model system for a fluorometric biosensor using permeabilized Zymomonas mobilis or enzymes with protein confined dinucleotides
Authors: Thordsen O. , Lee S. J. , Degelau A. , Scheper T. , Loos H. , Rehr B. , Sahm H. 
Published: December 2004

AbstractUsing permeabilized Zymomonas mobilis or glucose–fructose oxidoreductase isolated from this microorganism a model system for biosensors with a protein confined NADP(H) cofactor for the determination of glucose, fructose, gluconolactone, and sorbitol was developed. Either permeabilized microorganisms containing the oxidoreductase or the pure enzyme were confined via membrane separation in a small measuring chamber, that was integrated into a flow injection analysis system (FIA). The measuring principle was the monitoring of the NAD(P)H fluorescence, excited at 360 nm and measured at 450 nm. NADP(H), which is confined in the protein complex, was oxidized or reduced during the enzymatic reactions and the changes in the fluorescence intensity were related to the substrate concentration. The sensitivity of the system covered a range from 0.001 to 100 g/L of the analyte depending on substrate and operating conditions. The applicability of this model system for bioprocess monitoring was proved using samples from a Pseudomonas pseudoflava cultivation. © 1993 John Wiley & Sons, Inc.