bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of glucose fermentation by suspended and gel‐entrapped yeast cells: An in vivo nuclear magnetic resonance study
Authors: Taipa M. A. , Cabral J. M. S. , Santos H. 
Published: December 2004

AbstractPhosphorus‐31 nuclear magnetic resonance (31P NMR) was used to compare the anaerobic metabolism of glucose by suspended and gel‐entrapped Saccharomyces bayanus cells. The fermentation of glucose was carried out in a reaction system with continuous circulation through the NMR sample tube. The intracellular pH and the levels of some phosphorylated compounds were the levels of some phosphorylated compounds were noninvasively monitored by 31P NMR while glucose, fermentation products, and biomass were determined by analytic techniques comparisons showed that no significant differences are observed in the relative concentrations in the spectra, but distinct profiles for the variation of both intracellular and extracellular pH are found. The internal pH of immobilized cells is maintained at a constant value throughout the fermentation as opposed to freely suspended cells for which a steady decrease in the internal pH occurs. A faster and stronger acidification is also observed in the external medium of the assays with suspended cells. Furthermore, higher yields for ethanol and biomass production and lower yields of fermentation by‐products are obtained with immobilized cells. It is concluded that the higher intracellular pH achieved in the presence of the gel matrix had a regulatory effect on the metabolism which favored the ethanol production pathway. © 1993 John Wiley & Sons, Inc.
Diffusion of lactose in acidogenic biofilms
Authors: Yu Jian , Pinder K. L. 
Published: December 2004

AbstractEffective diffusivity of lactose in active acidogenic biofilms was measured at 35°C and pH 4.6 with a specially designed diffusion cell. The diffusion cell was designed and operated in such a way that the lactose concentrations on the surface and at the center of a living bacterial aggregate could be measured at steady state. As a model parameter in a widely accepted reaction–diffusion equation which describes lactose distribution in living biofilms, the effective diffusivity of lactose in the biofilms was found to be about 65% of the lactose diffusivity in free solutions. It was experimentally determined that the active biofilms had about 66% void volume made up of channels through which the lactose molecules were transported into the bacterial aggregates. Therefore, the decrease in lactose diffusivity was mainly caused by the biofilm's solid biomass fraction rather than the tortuosity of the channels. © 1993 John Wiley & Sons, Inc.
Biosorption of cadmium by biomass of marine algae
Authors: Holan Z. R. , Volesky B. , Prasetyo I. 
Published: December 2004

AbstractBiomass of nonliving, dried brown marine algae Sargassum natans, Fucus vesiculosus, and Ascophyllum nodosum demonstrated high equilibrium uptake of cadmium from aqueous solutions. The metal uptake of cadmium from aqueous solutions. The metal uptake by these materials was quantitatively evaluated using sorption isotherms. Biomass of A. nodosum accumulated the highest amount of cadmium exceeding 100 mg Cd2+/g (at the residual concentration of 100 mg Cd/L and pH 3.5), outperforming a commercial ion exchange resin DUOLITE GT–73. A new biosorbent material based on A. nodosum biomass was obtained by reinforcing the algal biomass by formaldehyde cross–linking. The prepared sorbent possessed good mechanical properties, chemical stability of the cell wall polysaccharides and low swelling volume. Desorption of deposited cadmium with 0.1−0.5M HCI resulted in no changes of the biosorbent metal uptake capacity through five subsequent adsorption/desorption cycles. There was no damage to the biosorbent which retained its macroscopic appearance and performance in repeated metal uptake/elution cycles. © 1993 Wiley & Sons, Inc.
Broad host range, regulated expression system utilizing bacteriophage T7 RNA polymerase and promoter
Authors: Pagratis Nikos C. , Revel Helen R. 
Published: December 2004

AbstractAn IPTF‐regulated broad host range expression system was constructed using compatible broad host range plasmids, the T7 RNA polymerase, and T7 promoter sequences. The system is implemented by the coexistence of two plasmids. The first contains the T7 RNA polymerase gene under the control of lacl or laclq genes and lacUV5 promoter. The second encodes the T7 promoter upstream of a multicloning site. IncP1 or IncP4 T7 promoter plasmids, and IncP1, IncP4 or IncW T7 RNA polymerase plasmids were constructed. The expression from the IncP1 promoter plasmids in the presence of the IncP4 polymerase plasmids was tested by in vivo lacZ fusions and vivo labeling of proteins. In this combination, the use of lacq improves the regulation levels in Escherichia coli, whereas, in Pseudomonas phaseolicola, a 28.5‐fold regulation was obtained with lacl, Although the level of lacZ expression from the T7 promoter in P. phaseolicola is low compared with E. coli, it is similar to levels obtained with the pm promoter in Pseudomonas putida when the differences in the copy number of the expression vectors are taken into consideration © 1993 Wiley & Sons, Inc.
Study of the enzymatic hydrolysis of cellulose for production of fuel ethanol by the simultaneous saccharification and fermentation process
Authors: Philippidis George P. , Smith Tammy K. , Wyman Charles E. 
Published: December 2004

AbstractThe biochemical conversion of cellulosic biomass to ethanol, a promising alternative fuel, can be carried out efficiently and economically using the simultaneous saccharification and fermentation (SSF) process. The SSF integrates the enzymatic hydrolysis of cellulose to glucose, catalyzed by the synergistic action of cellulase and β‐glucosidase, with the fermentative synthesis of ethanol. Because the enzymatic step determines the ethanol. Because the enzymatic step determines the availability of glucose to the ethanologenic fermentation, the kinetic of cellulose hydrolysis by cellulase and β‐glucosidase and the susceptibility of the two enzymes to inhibition by hydrolysis and fermentation products are of significant importance to the SSF performance and were investigated under realistic SSF conditions. A previously developed SSF mathematical model was used to conceptualize the depolymerization of cellulose. The model was regressed to the collected data to determine the values of the enzyme parameters and was found to satisfactorily predict the kinetics of cellulose hydrolysis. Cellobiose and glucose were identified as the strongest inhibitors of cellulase and β‐glucosidase, respectively. Experimental and modeling results are presented in light of the impact of enzymatic hydrolysis on fuel ethanol production. © 1993 Wiley & Sons, Inc.
A novel membrane bioreactor for detoxifying industrial wastewater: II. Biodegradation of 3‐chloronitrobenzene in an industrially produced wastewater
Authors: Livingston Andrew Guy 
Published: December 2004

AbstractA novel membrane bioreactor has been used for the treatment of an industrially produced wastewater arising in the manufacture of 3‐chloronitrobenzene. This wastewater is not amenable to direct biological treatment without some form pretreatment or dilution, due to the inorganic composition (pH <1, salt concentration 4% w/w) of the wastewater. In the membrane bioreactor, the organic pollutants are first separated from the wastewater by selective membrane permeation, and then biodegraded in the biological growth compartment of the bioreactor. At a wastewater flow rate of 64 mL h−1 (corresponding to a contact time of approximately 1.7 hours) over 99% of the 3‐chloronitrobenzene and over 99% of the nitrobenzene in the wastewater were degraded. Degradation of 3‐chloronitrobenzene was accompanied by evolution of chloride ions in a stoichiometric ratio. Both 3‐chloronitrobenzene and nitrobenzene degradation were accompanied by the evolution of carbon dioxide; approximately 80% of the carbon entering the system was oxidized to CO2 carbon. Analysis of mass transport across the membrane revealed that 3‐chloronitrobenzene and nitrobenzene are transported more rapidly than phenol. This is explained in terms of a resistances‐in‐series model, which shows phenol transfer to be rate limited by the membrane diffusion step, whereas the chloronitrobenzene and nitrobenzene transfer are rate limited by the liquid film mass transfer. © 1993 Wiley & Sons, Inc.
Synthesis and characterization of soluble concanavalin A oligomer
Authors: Pai Chaul Min , Jacobs Harvey , Bae You Han , Kim Sung Wan 
Published: December 2004

AbstractConcanavalin A, (Con A, MW 26,500/monomer unit) was crosslinked with glutaraldehyde to form soluble, high‐molecular‐weight (larger than MW 300,000) Con A Oligomers. After filtration to remove insoluble and low‐molecular‐weight portions (below 300,000 daltons), the size and molecular‐weight distribution were characterized by laser light scattering and gel‐filtration chromatography. The molecular‐size determined by laser light scattering ranged from 870 to 4070 Å, while the molecular weight determined by gel chromatography ranged from 6 × 105 to higher than 2 × 106 daltons. The affinity and kinetics of Con A oligomer binding to polysaccharide (glycogen) were evaluated by precipitation test and turbidity development, respectively. The binding with glycogen was strongest at neutral pH and showed similar activity to unmodified Con A molecules. The binding constants of α‐D‐glucose and succinyl‐aminophenyl α‐D glucopyranoside‐insulin to Con A oligomer were 1.0 × 103M−1 and 4.5 × 104M−1, respectively and the binding capacity of the oligomer was nearly 85% to 95% of monomeric Con A. The complexes of saccharides and soluble Con A oligomer were stable for at least 7 days. © 1993 Wiley & Sons, Inc.
Issues in the culture of the extremely thermophilic methanogen, methanothermus fervidus
Authors: Pepper Clinton B. , Monbouquette Harold G. 
Published: December 2004

AbstractBasic issues in the culture of the extremely thermophilic archaeon, Methanothermus fervidus, have been investigated, including culture medium formulation, substrate yield and product yield coefficient, growth rate and stoichiometry, and H2 uptake kinetics. The pH optimum for growth of this organism was estimated at 6.9. Growth medium buffered with PIPES instead of bicarbonate supported both increased growth rate and maximum biomass concentration. Substitution of titanium(III) citrate for the reducing agent sodium sulfide improved culture performance as well. However, independent adjustment of iron and nickel concentrations from 11 to 111 μM, respectively, and carbon dioxide partial pressure from 5 to 20 psia did not impact the culture of M. fervidus significantly. An elemental balance approach was utilized to aid in design of a defined medium to support growth to a target maximum biomass concentration of at least 1.0 g dry wt/L. The growth of this organism was limited by H2 availability in this reformulated culture medium. The maximum growth rate and biomass concentration achieved in anaerobic vials with the defined medium was 0.16 h−1 and 0.74 g dry wt/L, respectively. This maximum biomass concentration was a 72% improvement over that obtained with a literature‐based defined medium. The Monod parameter, Ks, with H2 as limiting substrate, was estimated at 1.1 ± 0.4 psia (55 ± 20 μM in the broth), based on a H2 consumption study. Representative values for the substrate yield, Y, and product yield coefficient, YX, were determined experimentally to be 1.78 ± 0.04 g dry wt/mol CO2, and 0.52 ± 0.01 mol CH4/g dry wt, respectively. A bench‐scale fermentation system suitable for the culture of extremely thermophilic anaerobes was designed and constructed and proved effective for the culture of M. fervidus. © 1993 Wiley & Sons, Inc.
Productivity of outdoor algal cultures in unstable weather conditions
Authors: Lee Yuan‐Kun , Low Chin‐Seng 
Published: December 2004

AbstractIn the outdoor cyclic fed batch cultures of Chlorella pyrenoidosa, some typical growth kinetics patterns in unstable weather conditions were observed. On cloudy days, the biomass output rate (R) was low, but the bioenergetic growth yield (Y) was generally high. In the cloudy morning‐sunny afternoon condition, the values of Y were low, especially in the afternoon. In the sunny morning‐cloudy afternoon condition, both R and Y were high. A few very high short‐term Y values were measured during the cloudy the cloudy afternoon. © 1993 Wiley & Sons, Inc.
Modeling and optimization of cloned invertase expression in Saccharomyces cerevisiae
Authors: Patkar Anant , Seo Jin‐ho , Lim Henry C. 
Published: December 2004

AbstractThe aim of this study is to determine the medium feeding strategy to maximize the invertase productivity of recombinant Saccharomyces Cerevisiae using a fed‐batch mode of operation. The yeast contains the plasmid, pRB58, which contains the yeast SUC2 gene, coding for the enzyme invertase. The expression of this gene is repressed at high glucose levels. A Goal‐oriented model is development to describe the kinetics of fed‐batch fermentations. This simple model could quantitatively describe previous experimental results. A conjugate gradient algorithm is then used, in conjunction gradient algorithm is then used, in conjunction with this mathematical model, to compute the optimum feed rate for maximization of invertase productivity. The optimal feeding procedure results in an initial high cell growth phase followed by a high invertase production phase. © 1993 Wiley & Sons, Inc.
Nutrient‐split feeding strategy for dialysis cultivation of Escherichia coli
Authors: Ogbonna James Chukwuma , Märkl Herbert 
Published: December 2004

AbstractReduction in nutrient loss during dialysis cultivation of Escherichia coli on a glycerol medium was investigated. A dialysis reactor with an inner fermentation and an outer dialysis chamber was used. Aerobic condition was maintained by limiting the glycerol feed rate to an optimum value which was estimated from the oxygen requirements for glycerol oxidation and oxygen transfer capacity of the reactor. High reduction in nutrient loss was achieved by using water as the dialyzing fluid. However, osmotic movement of water from the dialysis to the fermentation chamber was observed, and the final cell concentration was low. With a nutrient‐split feeding strategy (feeding glycerol directly to the fermentation chamber and dialyzing with salt solution), glycerol loss was small, there was no osmotic flux of water to the fermentation chamber, and the cell concentration was high. Both glycerol and salt loss could be avoided, and a cell concentration of 170 g/L was obtained when the dialysis process was substituted by addition of XAD adsorbents to the dialysis chamber. Application of this nutrient‐split feeding strategy to cell cultivation in a stirred tank reactor, coupled with dialysis in external dialyzer modules, resulted in low cell concentrations. © 1993 Wiley & Sons, Inc.
Experimental determination of flux control distribution in biochemical systems: In vitro model to analyze transient metabolite concentrations
Authors: Delgado Javier , Meruane Jorge , Liao James C. 
Published: December 2004

AbstractDetermination of the control coefficients allows the identification of rate‐controlling steps in a reaction system. However, the measurement of the flux control coefficients in a biochemical system is not a trivial task, except for some special cases. We have developed a theoretical basis for the direct determination of these coefficients from dynamic responses. In order to show the validity of this methodology experimentally, the dynamic approach is applied to an in vitro reconstituted partial glycolytic pathway to determine the flux control coefficients of hexokinase and phosphofructokinase. It is shown that the dynamic approach gives consistent results, which agree well with values obtained by the direct enzyme titration method. The detailed procedure and potential applications to other systems, such as immobilized enzyme or cell reactors, are discussed. © 1993 Wiley & Sons, Inc.
Comparison of soluble and immobilized trypsin kinetics: Implications for peptide synthesis
Authors: Sears Pamela S. , Clark Douglas S. 
Published: December 2004

AbstractThe protease trypsin was immobilized to porous glass in both the presence and absence of acetylated soybean trypsin inhibitor (STI) to determine whether immobilization could alter enzyme activity in favor of aminolysis over hydrolysis. Actiive‐site titration with 4‐methylumbelliferylguanidinobenzoate (MUGB) showed that only about 10% of immobilized trypsin had catalytic activity. Immobilization in the presence of STI produced a higher yield of active enzyme accessible to the inhibitor but did not increase the total yield of MUGB‐active immobilized enzyme. Thus, enzyme inactivation upon immobilization could not be attributed to an inaccessible enzyme orientation, nor did STI prevent inactivation by stabilizing the active‐site conformation. Kinetic parameters were determined for soluble and immobilized trypsin for two esters, N‐tosyl‐L‐arginine methyl ester (TAME) and N‐benzoyl‐L‐arginine ethyl ester (BAEE), and two amides, N‐benzoyl‐L‐arginine p‐nitroanilide (BAPNA) and N‐t‐boc‐leucylglycylarginine p‐nitroanilide (LGRNA). In all cases, immobilization caused a greater decrease in kcat for amidase activity than for esterase activity. The ratio [kcat/ Km (ester)]/[kcat/Km (amide)] increased slightly or stayed the same (for I.GRNA) or decreased sharply (for BAPNA). Including STI during immobilization had little effect on the active enzyme's intrinsic kinetics. A direct comparison of energy diagrams and free energies of activation for BAEE and BAPNA indicates that immobilization raises the free energy barriers for both amide and ester hydrolysis and lowers the energy barrier for aminolysis. In practice, these effects should lower the amidase activity and increase the aminolysis–hydrolysis ratio, rendering the immobilized enzyme a more efficient catalyst for peptide synthesis. © 1993 John Wiley & Sons, Inc.
Effect of operating conditions on solid substrate fermentation
Authors: Sargantanis John , Karim M. N. , Murphy V. G. , Ryoo D. , Tengerdy R. P. 
Published: December 2004

AbstractIn this work the effects of environmental parameters on the performance of solid substrate fermentation (SSF) for protein production are studied. These parameters are (i) air flow rate, (ii) inlet air relative humidity, (iii) inlet air temperature, and (iv) the heat transfer coefficient between the outer wall of the fermentor and the air in the incubator. The air flow is supplied to effect cooling of the fermented mass by evaporation of water. A dynamic model is developed, which permits estimation of biomass content, total dry matter, moisture content, and temperature of the fermented matter. The model includes the effects of temperature and moisture content on both the maximum specific growth rate and the maximum attainable biomass content. The results of the simulation are compared with actual experimental data and show good agreement with them. The most important conclusions are that (i) the evaporative cooling of the biomass is very effective for temperature control and (ii) the air flow rate and the heat transfer coefficient have strong effects but they affect the biomass morphology and are not controllable easily. Also, a simple technique for the determination of the optimum temperature and moisture content profile for cell protein production is applied. The simulated biomass production increases considerably employing the optimum temperature and moisture content profiles. The ultimate goal is to implement the determined effects of the environmental parameters on the SSF biomass production and the temperature and moisture variation profiles to effectively control the SSF and optimize the biomass production. © 1993 John Wiley & Sons, Inc.
Immobilization of β‐galactosidase for application in organic chemistry using a chelating peptide
Authors: Piesecki Susan , Teng Wen‐Yu , Hochuli Erich 
Published: December 2004

AbstractThe strong interaction of hexa‐histidine fusion proteins with metal chelate adsorbents was utilized to immobilize β‐galactosidase with a hexa‐histidine peptide at the N‐terminus to the Ni2+‐nitrilotriacetic acid adsorbent. The fusion protein was cloned and expressed in Escherichia coli. The purified soluble fusion protein showed the same specific activity as the purified β‐galactosidase and retained 64 percent of its β‐galactosidase activity when bound to the adsorbent. To demonstrate the potential of the immobilized β‐galactosidase in organic chemistry, allyl‐β‐D‐galactosidase was synthesized from lactose and allyl alcohol on a gram scale. The same enzyme preparation was reused in three subsequent batches to prepare the model compound with high yield. © 1993 John Wiley & Sons, Inc.
Some factors determining protein aggregation during ultrafiltration
Authors: Kim K. J. , Chen V. , Fane A. G. 
Published: December 2004

AbstractThe factors contributing to protein aggregation in albumin ultrafiltration were investigated as a function of operation conditions. The nature of protein deposits was examined by electron microscopy. Protein aggregation appears to occur as a result of rapid supersaturation of protein molecules and high solvent velocity (shear) in the concentrated layer near the membrane surface. The shear occurring in the solvent flow on the membrane surface probably unfolds protein molecules and thus promotes flocculation due to collision between particles. © 1993 John Wiley & Sons, Inc.
Image analysis to quantify and measure UASB digester granules
Authors: Dudley Barry T. , Howgrave‐Graham Alan R. , Bruton Anthony G. , Wallis Frederick M. 
Published: December 2004

AbstractTwo‐dimensional image analysis was applied to counting, sizing, and density determinations of granules in full‐scale and laboratory‐scale upflow anaerobic sludge blanket (UASB) digesters. An advantage of this technique for monitoring laboratory‐scale digester sludge is the small amount of material required for analysis. Quantification of number of granules using this method correlated well with dry weight determinations (r = 0.989). Distinguished granule size increased with time throughout the digestion process, supported by dry weight determinations which indicated an increase in biomass. The monitoring of granule density may reveal subtleties of the selection pressure placed on granules not noticed previously. © 1993 John Wiley & Sons, Inc.
Determination of cellular rate distributions in microbial cell populations: Feeding rates of ciliated protozoa
Authors: Hatzis Christos , Sweeney Pamela J. , Srienc Friedrich , Fredrickson A. G. 
Published: December 2004

AbstractA novel procedure is proposed for determining distributions of rate properties and correlations of rate with state properties of microbial cell populations. The procedure is novel in that it uses transient data, and thus, it does not require that the population be in balanced growth, although it requires that the population structure does not change during the short transient experiment. The procedure is applied to populations of the ciliated protozoan Tetrahymena to determine ingestion rate variability. The number of ingested microspheres per cell and the single‐cell protein content—an indicator of cell size—were directly determined with dual‐color flow cytometry. The proposed technique revealed the correlation pattern of the particle ingestion rate with cell size. In particular, ingestion rate was found to be positively correlated with cell size for the smaller feeding cells and to be uncorrelated with size for the larger cells. Using the fact that particle uptake from dilute particle suspensions is a Poisson random process, we determined that the coefficient of variation of the distribution of ingestion rates within the feeding population is about 50%. It was concluded that the dynamics of particle ingestion can be accurately described only if it is realized that particle ingestion rates are distributed. © 1993 John Wiley & Sons, Inc.