bluuebunny/crossref_metadata_2025_split huggingface dataset:
Energetic and rate effects on methanogenesis of ethanol and propionate in perturbed CSTRs
Authors: Smith Daniel P. , McCarty Perry L. 
Published: May 2005

AbstractEnergetic and reaction‐rate interactions between hydrogenic (hydrogen‐producing) and hydrogenotrophic (hydrogen‐consuming) bacteria were investigated in five perturbation experiments performed on steady‐state, mixed‐culture methanogenic CSTRs receiving ethanol, propionate, or both hydrogenic substrates. When a large quantity of propionate was suddenly added to a propionatefed CSTR, P increased to 10−4 atm and propionate oxidation remained energetically favorable. When ethanol was added to a CSTR receiving ethanol, P rose to 6.3 × 10−3 atm within 5 h. In both perturbations, P remained at levels such that oxidation of the hydrogenic substrate remained energetically favorable throughout the transient. Sudden increase in ethanol concentration in the ethanol‐ and propionate‐fed CSTR resulted in an increase in P such that propionate oxidation became energetically unfavorable and was blocked. Propionate utilization resumed when the added ethanol was depleted and P returned to its previous steady‐state levels. Ethanol perturbation of ethanol‐ and propionate‐fed CSTRs led to the formation of reduced products, including n‐propanol and four‐through seven‐carbon n‐carboxylic acids, when P was elevated; these products disappeared after P returned to previous, steady‐state levels. The transformations were consistent with reaction energetics. Reduced product formation may have been a sink for reducing equivalents, as an alternative to oxidation for propionate utilization, as indicated by an electron equivalents balance over the time course of experiments.
Electrophoretic and enzymatic studies on the crude extracellular enzyme system of the cellulolytic bacterium Cellulomonas sp. ATCC 21399
Authors: Poulsen O. M. , Petersen L. W. 
Published: May 2005

AbstractCellulomonas sp. ATCC 21399 produced extracellular enzyme activities against Avicel, H3PO4‐swollen Avicel, carboxymethylcellulose, (1‐3, 1‐4)‐β‐D‐heteroglucan, xylan, galactomannan, and amylose drying growth on microcrystalline cellulose. No extracellular cellobiase activity was produced. Crossed immunoelectrophoresis of the crude extracellular enzyme system revealed 15 immunologically distinct immunoprecipitates. The immunoprecipitates of endoglucanase A, endoglucanase B and the xylanase appeared heterogeneous with several optima, whereas the immunoprecipitates of endoglucanase C and the amylase appeared homogeneous. The heterogeneity of endoglucanase A, endoglucanase B and xylanase was also visualized using electrofocusing‐immunoelectrophoresis. Electro‐focusing could resolve the activity against carboxymethylcellulose into six peaks, whereas only one peak of activity against Avicel was observed. The later peak coincided with the major peak of activity against carboxymethylcellulose with isoelectric point between pH 4.0–5.0.
Mode of action of endopolygalacturonase immobilized by adsorption and by covalent binding via amino groups
Authors: Rexová‐Benková L. , Omelková J. , Veruovič B. , Kubánek V. 
Published: May 2005

AbstractAction pattern of endopolygalacturonase (E.C.3.2.1.15) immobilized by adsorption on porous powdered poly(ethyleneterephthalate) and covalently bound via amino groups on poly(2, 6‐dimethyl‐p‐phenyleneoxide) and poly(6‐caprolactame), respectively, were investigated in suspension and packed columns using polymeric and oligomeric D‐galactosiduronates as substrates. The covalent binding invariably led to a lowering of randomness of degradation of high‐molecular substrates and loss of specificity of (3 + 1) splitting of tetra(galactosiduronic acid), typical of the free enzyme. In the adsorbed endopolygalacturonase the degree of randomness of degradation of D‐galacturonan and Km,app value were dependent on the substrate transfer; the former parameter increased, the later decreased with increasing flow‐rate of the substrate through the immobilized enzyme bed. The action pattern on low‐molecular substrates was not altered. The changes in action pattern of the covalently immobilized endopolygalacturonase are ascribed to sterical limitations resulting from a binding of the enzyme molecule in the proximity of its active site. In endopolygalacturonase bound to the support by hydrophobic interactions external diffusion effects are regarded the factors governing the enzyme action.
Dewatering of biological slurry by using water‐absorbent polymer gel
Authors: Huang Xia , Akehata Takashi , Unno Hajime , Hirasa Okihiko 
Published: May 2005

AbstractA new concentrating/dewatering process utilizing water‐absorbent polymer gels as dewatering media for biological slurries is proposed. The polymer gel applied to the process should be of porous structure for rapid water‐absorption and of larger size for easier separation of gel from slurry. Poly(vinylmethylether) gel (PVMEG) prepared by γ‐ray irradiation was found to be suitable for the purpose. PVMEG swelled or shrunk reversibly in response to temperature and its transition temperature was 310K. Slurries of different properties were dewatered quite well by applying PVMEG. The water‐absorbability of the gel was unaffected by the properties of organic substances contained in the slurries. An engineering calculation of the proposed dewatering process, which was called “gel dewatering process,” revealed that the process was promising for concentrating/dewatering microbe‐rich slurries in the respect that it would be composed of compact and simple apparatuses and be an energy saving system.
Experimental and simulation studies of multivariable adaptive optimization of continuous bioreactors using bilevel forgetting factors
Authors: Chang Yong K. , Lim Henry C. 
Published: May 2005

AbstractA multivariable on‐line adaptive optimization algorithm using a bilevel forgetting factor method was developed and applied to a continuous baker's yeast culture in simulation and experimental studies to maximize the cellular productivity by manipulating the dilution rate and the temperature. The algorithm showed a good optimization speed and a good adaptability and reoptimization capability. The algorithm was able to stably maintain the process around the optimum point for an extended period of time. Two cases were investigated: an unconstrained and a constrained optimization. In the constrained optimization the ethanol concentration was used as an index for the baking quality of yeast cells. An equality constraint with a quadratic penalty was imposed on the ethanol concentration to keep its level close to a hypothetical “optimum” value. The developed algorithm was experimentally applied to a baker's yeast culture to demonstrate its validity. Only unconstrained optimization was carried out experimentally. A set of tuning parameter values was suggested after evaluating the results from several experimental runs. With those tuning parameter values the optimization took 50–90 h. At the attained steady state the dilution rate was 0.310 h−1 the temperature 32.8°C, and the cellular productivity 1.50 g/L/h.
The physiology of lactate production by Lactobacillus delbreuckii in a chemostat with cell recycle
Authors: Major Nicolas C. , Bull Alan T. 
Published: May 2005

AbstractThe physiology of lactate production by Lactobacillus delbreuckii NRRL B‐445 in a continuous fermenter with partial cell recycle has been studied and compared with that observed in a conventional chemostat. Partial cell recycle was achieved using a hollow‐fiber ultrafiltration cartridge. The biomass growth yield was reduced in the recycle fermenter while culture viability and the cellular content of polysaccharide, protein, carbon, and nitrogen remained constant, suggesting an enlarged specific rate of glucose consumption for nonanabolic (e.g., maintenance) functions. The volumetric productivity of lactate was enhanced in the recycle fermenter due to the complete utilization of glucose. The yield of lactate from biomass and the molar product ratio, lactate: ethanol plus acetate, decreased with increasing recycle ratio. Enhanced formation of ethanol and acetate occurred in the recycle fermenter although lactate remained the major product. The change in product profile was due to glucose limitation. The specific activity of lactate dehydrogenase remained constant during recycle fermentation. These physiological observations have implications for the future application of cell recycle to production processes.
An adaptive state estimator for detecting contaminants in bioreactors
Authors: Chattaway Thomas , Stephanopoulos Gregory N. 
Published: May 2005

AbstractAn algorithm is presented for detecting the appearance of contaminants during batch or fed‐batch fermentations, using only presently available on‐line measurements. Its adaptive nature enables it to rely on almost no prior knowledge of the real process. The necessary on‐line measurements are total biomass and its production rate; it is also shown how a physical variable such as oxygen uptake can be used alone instead. The algorithm's properties are studied theoretically and through simulations. These were confirmed by on‐line experimental results, obtained with a Yeast culture, both pure and contaminated by a Bacteria. The algorithm does not detect contaminants when none are there, and it also provides a convergent estimate of a pure culture's specific growth rate. Contaminated cultures are recognized by the algorithm, and this detection can be made more or less conservative. After detection, the various estimates may diverge, due to general observability difficulties, though this divergence can itself be monitored. Moreover, the algorithm is easy to tune and its qualitative behavior is quite insensitive to its adjustable parameters. A practical criterion and scheme for implementation are proposed. The generality of the approach, which far exceeds the experimental system used, is finally discussed.
Mass transfer studies using cloned‐luminous strain of Xanthomonas campestris
Authors: Vashitz O. , Sheintuch M. , Ulitzur S. 
Published: May 2005

AbstractMeasurements of mass transfer in a highly viscous pseudoplastic broth, which is typical to Xanthomonas campestris fermentations, are difficult to obtain by conventional methods and little data is available. A novel research method that uses bioluminescence for mass transfer studies has been developed. A plasmid carrying the luminescence operon of marine luminous bacteria is introduced into an industrial bacteria, X. campestris. Besides producing the polysaccharide xanthangum, the bioluminescent X. campestris emits measurable light. Monitoring the luminescence is a simple, noncontaminating nondestructive and very sensitive indicator of the metabolic activity of the culture during fermentation. Energy drain due to bioluminescence is very low; growth rate and polysaccharide production rate are close to those of the wild‐type strain.Oxygen and substrate mass transfer are determined by inducing step or periodic fluctuations in their concentration and measuring the resultant luminescence response. Oxygen mass transfer coefficients show linear dependence on Reynolds number and an exponential dependence on the average shear rate. Viscosity effect is small at high viscosities but increases rapidly below 10 Pa‐s. The influence of oxygen uptake rate is studied.Mass transfer of the limiting component (ammonium ions) is analyzed under pulsating feed conditions. The luminescence declines, following a feed pulse, due to energy investment in active transport of ammonium ions through the cell membrane, it regenerates then to its baseline. The relation between mass transfer and luminescence fluctuation is elucidated.
Bacterial growth on lactose: An experimental investigation
Authors: Straight Jeffrey V. , Ramkrishna D. , Parulekar Satish J. , Jansen Norman B. 
Published: May 2005

AbstractA wild‐type strain of Klebsiella oxytoca growing aerobically in batch culture has exhibited intermittent or oscillatory growth while growing on lactose at concentrations on the order of 1 g/L or less. In two‐substrate experiments, preferred growth on glucose followed by growth on lactose also produced oscillatory growth behavior during the lactose growth phase at lactose concentrations of 1 g/L or less. Only oscillations in cell density have currently been observed. Alkalinization of the medium during growth on lactose indicated the presence of lactose active transport. The observed intermittent growth was reduced or removed during growth on lactose after preferred growth on galactose or in a medium containing 50 mM NaCl. Results suggested that the presence of an intracellular energy source or a sufficient ΔpH buffer may alleviate growth inhibition when transport and growth processes compete for essential energy resources during growth on lactose.
Alcohol adsorption on softwood lignin from aqueous solutions
Authors: Yang Y. , Ladisch M. R. , Ladisch C. M. 
Published: May 2005

AbstractLignin prepared by acid and enzyme hydrolysis of a softwood mixture adsorbs acetone, butanol, and other alcohols while showing only a slight uptake of glucose. Adsorption of butanol is independent of temperature in the range of 30‐65°C. The Polanyi theory fits adsorption for the linear alcohols methanol through hexanol with values of AS and Δμ ranging from 2.6 to 26 J mol−1 K−1and −0.8 to −8 kJ/mol. The adsorption capacity is given by Q (g alcohol/g lignin) = KC*. Where C* is the equilibrium alcohol concentration (g/mL), K = εWexp (Δ/R), and εw is the porosity of the lignin (0.23‐0.42 mL/g). The value of the adsorption capacity constant K for n‐butanol ranges from 1.3 to 2.7 mL/g on sorbent containing 26‐72% lignin, while ethanol is 0.5‐0.73, acetone is 0.62‐1.0, and glucose is 0.35. Adsorption is shown to occur through combined hydrophobic and hydrophilic interactions of the alkyl and hydroxyl groups, respectively, of the adsorbate with the lignin. Consequently, for the alcohols methanol to hexanol, we present the capacity constant K[=K(R) + K(OH)] as a sum of an alky! adsorption constant (0.1‐9.5 mL/g) and a hydrophilic (0.40‐0.50 mL/g) contribution. This approach may be applicable to organic acids. Lignin's sorbent properties have potential to moderate product inhibition in the anaerobic acetone‐butanol‐ethanol (ABE) fermentation.
Modeling analysis of an intercalated‐spiral alternate‐dead‐ended hollow fiber bioreactor for mammalian cell cultures
Authors: Brotherton John D. , Chau Pao C. 
Published: May 2005

AbstractThe model analysis of a bioreactor with two intercalated‐spiral sets of hollow fibers with alternated dead ends is presented. Design equations are derived based on a model with two jumped fibers and an approximation of the fluid mechanics with a small fiber radius‐to‐length ratio. The performance of the bioreactor is simulated with and without cell growth utilizing a segregated radial flow model in the extracapillary space. The pressure modulus, the wall Peclet number, the Thiele modulus, and the Monod constant are used as model parameters. The results can be used to assess the proper choice of fiber permeability, fiber length, fiber spacing, and flow velocity.
Comparison of wild‐type and Reg 1 mutant saccharomyces cerevisiae metabolic levels during glucose and galactose metabolism using 31P NMR
Authors: Shanks Jacqueline Vanni , Bailey James E. 
Published: May 2005

AbstractThe reg 1 mutation will allow the expression of a cloned gene on a plasmid under the control of a GAL promoter in the presence of glucose. The metabolism of wild‐type and reg l mutant strains was examined by in vivo 31P nuclear magnetic resonance (NMR) spectroscopy. Transient profiles of glucose 6‐phosphate, fructose 6‐phosphate, fructose 1, 6‐diphosphate, and 3‐phosphoglycerate indicated that glucose was processed differently for the reg 1 strain despite similar cytoplasrnic pH values and ATP levels. Intracellular phosphate became depleted in the transition to quasi‐steady state and limited glycolysis in the reg 1 strain. The glucose uptake step or hexokinase step appears to be altered in the reg 1 strain. The reg 1 strain utilized galactose faster than the wild‐type strain under the conditions used for NMR analysis. These results are consistent with the hypothesis that the REG 1 product operates early in the regulatory circuitry for glucose repression. This study illustrates the usefulness of transient information provided by NMR in understanding changes in the metabolism of genetically manipulated organisms.
The loss of antibody productivity in continuous culture of hybridoma cells
Authors: Frame Kelly K. , Hu Wei‐Shou 
Published: May 2005

AbstractTwo hybridoma lines, HB8178 and AFP‐27, were grown in continuous culture. The concentrations of viable cells as well as those of various nutrients and metabolites reached steady‐state values. The concentrations of either total IgG or antigen‐specific antibody, however, failed to reach steady‐state values but rather continuously decreased over the course of the cultures. The fraction of antibody‐producing cells in the total cellular population also continuously decreased in the AFP‐27 cultures. Comparison of the specific antibody productivity based on either the entire population or the antibody‐producing fraction of the population over time suggests that the decrease in productivity was at least partly due to the occurrence of a nonproducing subpopulation of cells.
Continuous measurement of dissolved H2 in an anaerobic reactor using a new hydrogen/air fuel cell detector
Authors: Pauss A. , Samson R. , Guiot S. , Beauchemin C. 
Published: May 2005

AbstractA miniature fuel cell, using a hydrophobic Teflon® membrane, designed to continuously measure dissolved H2 in nonbiological media, was tested for use in anaerobic digestion conditions. In water, this detector responds quickly and efficiently to variation of hydrogen concentration in the range from 80 to 770 nM The media used, and the metabolites or products found in anaerobic digestion media, i. e. inorganic carbon and phosphate buffers, formate, acetate, and dissolved methane, did not interfere with the signal of the detector cell. Dissolved hydrogen sulfide did not poison the cell but was detected. In spite of the detector's high sensitivity to hydrogen (about 21,000 times higher for hydrogen than for hydrogen sulfide), interferences can occur in media containing high sulfide levels.In a methanogenic reactor, the detector cell response to dissolved hydrogen was fast and reliable with time. The observed values ranged values ranged from 2 to 3.5μM. Dissolved hydrogen concentrations were 40 to 70 times higher than values calculated from measured hydrogen partial pressures and Henry's coefficient, suggesting a limitation of the process in the hydrogen transfer from the liquid to the gaseous phase.
Liquid circulation in external‐loop airlift bioreactors
Authors: Kawase Yoshinori 
Published: May 2005

AbstractA simple model for prediction of liquid velocity in external‐loop airlift bioreactors has been developed. Theoretical correlations for friction factor of gas‐non‐Newtonian two‐phase flows and for liquid velocity in the riser were derived using the concept of an eddy diffusivity. The predictions of the proposed model were compared with the available experimental data for the friction factor and the liquid velocity in the riser of external‐loop airlift contactors. Satisfactory agreement was obtained.
Asymmetric reduction of ketones with resting cells of Sulfolobus solfataricus
Authors: Trincone Antonio , Lama Licia , Lanzotti Virginia , Nicolaus Barbara , De Rosa Mario , Rossi Mosé , Gambacorta Agata 
Published: May 2005

AbstractThe method of resting cells has been of interest in the development of biocatalysts applied to organic reactions.This article deals with the use of resting cells of a thermophilic archaebacterium Sulfolobus solfataricus, in the asymmetric reduction of acyclic, cyclic, and aromatic ketones. The system allows the continuous regeneration of endogenous coenzyme with the coupled substrate approach. The results indicate that the direction of hydride attack was equatorial on the re face of the carbonyl group of substrates producing (S)‐alcohols with a good optical yield. A convenient system for the reuse of resting cells has been set out to synthesize (S)‐alcohols on a preparative scale.
Oxygen transfer enhancement in aqueous/perfluorocarbon fermentation systems: I. experimental observations
Authors: Junker Beth H. , Hatton T. Alan , Wang Daniel I. C. 
Published: May 2005

AbstractA new fiber‐optic dissolved oxygen sensing technique was applied to the study of two‐phase aqueous/perfluorocarbon (pfc) dispersions. These dispersions were examined for their oxygen transfer enhancement capability in the absence and presence of an oxygen‐consuming reaction. For the pfc‐in‐water dispersions, oxygen uptake rate (OUR) enhancements were equal both with and without oxygen‐consuming cells present in the aqueous phase. In contrast, for water‐in‐pfc dispersions, OUR enhancements inthe presence of reaction were limited by oxygen diffusion across the aqueous phase droplets. Nevertheless, enhancement factors of 5–10 on an aqueous phase volume basis were obtained in a 75% pfc dispersion.These oxygen transfer enhancements were directly translatable into enhancements in overall fermenter productivity for actual microbial cultivation systems.
Drying of ethanol vapors by adsorption on corn meal
Authors: Hassaballah A. A. , Hills J. H. 
Published: May 2005

AbstractExperiments have been carried out on a laboratory‐scale adsorber packed with 3.3 kg cornmeal. The effects of varying particle size, feed concentrations and flow rates, and regeneration conditions on the product quality and breakthrough times were investigated. It was found that 85% (w/w) vapor feed gave the best product, and product yields of up to 99.8% (w/w) alcohol were obtained at energy costs as low as 4.0 MJ kg−1. It is suggested how this figure could be improved.
Multipoint attachment to a support protects enzyme from inactivation by organic solvents: α‐Chymotrypsin in aqueous solutions of alcohols and diols
Authors: Mozhaev Vadim V. , Sergeeva Mariya V. , Belova Alla B. , Khmelnitsky Yuri L. 
Published: May 2005

AbstractInactivation of α‐chymotrypsin in aqueous solutions of alcohols and diols proceeds both reversibly and irreversibly. Reversible loss of the specific enzyme activity results from conformational changes (unfolding) of the enzyme detected by fluorescence spectroscopy. Multipoint covalent attachment to the matrix of polyacryl‐amide gel by copolymerization method stabilizes α‐chymotrypsin from denaturation by alcohols, the stabilizing effect increasing with the number of bonds between the protein and the support. Immobilization protects the enzyme also from irreversible inactivation by organic solvents resulting from bimolecular aggregation and autolysis.