bluuebunny/crossref_metadata_2025 huggingface dataset:
Separation of egg yolk immunoglobulins using an automated liquid chromatography system
Authors: Fichtali J. , Charter E. A. , Lo K. V. , Nakai S.
Published: December 2004

An automated liquid chromatography system was developed to carry out the separation of an egg yolk immunoglobulin (IgY) using cation exchange media. Industrially separated egg yolk was diluted 10 times with distilled water, the pH adjusted to 5.5, and the water‐soluble protein fraction separated from lipoproteins by sedimentation. The supernatant was filtered and then applied to a column packed with a cation exchanger within an automated liquid chromatography system. Different operating conditions were investigated using phosphate buffer in order to assess the effect on recovery and purity. Fractions as pure as 80% could be collected and a recovery of the chromatography step of about 65% was obtained for a purity of 60% using either a linear or step gradient. The overall recovery for the process was 34% if one‐step dilution/extraction is used for lipoprotein separation by sedimentation, and 51% if two‐step dillution/extraction is used. Further improvement of the yield to about 60% is possible using centrifugation for lipoprotein separation. The automated system confers many advantages, the key elements being the time savings and accurate control of the process. © 1992 John Wiley & Sons, Inc.
Evolutionary operation (EVOP) to optimize three‐dimensional biological experiments
Authors: Banerjee Rintu , Bhattacharyya B. C.
Published: December 2004

Evolutionary operation (EVOP) is used as an efficient technique for optimization of three variable experimental parameters using two‐level factorial designs with center points. For metabolic function like enzyme synthesis by microorganisms, small amounts of metal ions, surfactants, and vitamins act as inducers. The desired quantities of these chemicals are, however, species dependent and have to be found out or each microorganism. By employing the EVOP technique, the requirements of these chemicals have been optimized for the production of protease by Rhizopus oryzae (RO, IIT KGP). © 1993 John Wiley & Sons, Inc.
Enzymatic production of cyclodextrins from milled corn starch in an ultrafiltration membrane bioreactor
Authors: Kim Tae‐Jong , Lee Yun‐Dong , Kim Hak‐Sung
Published: December 2004

Cyclodextrin glycosyltransferase (CGTase) was found to be severely inhibited by cyclodextrins. In order to increase the conversion yield by reducing product inhibition and reuse the CGTase in the production of cyclodextrins from milled corn starch, an ultrafiltration membrane bioreactor system was employed. In a batch operation with ultrafiltration, the conversion yield was increased 57% compared with that without ultrafiltration. Operating conditions for the continuous production of cyclodextrins in the membrane bioreactor were optimized by taking into consideration the filtration rate and the conversion yield as follows: initial starch concentration, 7% (w/v); starch feeding rate, 240 mg/h; CGTase loading, 350 units/initial gram starch. When cyclodextrins were continuously produced in the membrane bioreactor under optimized conditions, 340 units of CGTase was require to produce 1 g of cyclodextrins for 48 h, while in the case of conventional batch operation, 1 g of cyclodextrins was produced for 24 h by 1410 units of CGTase. © 1993 John Wiley & Sons, Inc.
The effect of organic solvents on the equilibrium position of enzymatic acylglycerol synthesis
Authors: Janseen Anja E. M. , Van der Padt Albert , Van Sonsbeek Henk M. , Van't Riet Klaas
Published: December 2004

The effect of organic solvents on the equilibrium position of lipase‐catalyzed esterification of glycerol and decanoic acid has been investigated. The reaction is carried out in an aqueous‐organic two‐phase system. In polar solvents, high mole fractions of monoacylglycerol and low mole fractions of triacylglycerol and measured, while in nonpolar solvents, the measured differences in the mole fractions of monodi‐, and triacylglycerols are less. There is a good correlation between the ester mole fractions at equilibrium and the log P of the solvent (partition coefficient in n‐octanolwater), however, only if the group of tertiary alcohols is excluded. In the plot of the easter mole fractions as a function of the logarithm of hte solubility of water in the organic solvent, the tertiary alcohols can be included; however, in this case other deviations appear.

For the prediction of the effect of organic solvents on the ester mole fractions at reaction equilibrium in nondilute reaction systems with a water activity below 1, the program TREP (Two‐phase Reaction Equilibrium Prediction) is developed, which is based on the UNIFAC group contribution method. With this model the equilibrium data are essentially predicted from basic thermodynamic data. The required equilibrium constants are estimated from experiments without an organic solvent in the reaction medium. The mole fractions calculated by TREP show the same trends as the experimentally measured mole fractions; however, some variation is observed in the absolute values. These deviations may be due to inaccuracies in the UNIFAC group contribution method. TREP is found to be a correct method to predict within some limits the ester mole fractions at equilibrium for all mixtures of solvents, substrates, and products. The production of monoester can be enhanced in reaction system with a sufficient high concentration of a polar solvent. In experiments with a triglymeto‐decanoic acid ratio of 5, almost no di‐and triesters can be detected at equilibrium. © 1993 John Wiley & Sons, Inc.
Kinetic characterization of baculovirus‐induced cell death in insect cell cultures
Authors: Wu Suh‐Chin , Dale Bruce E. , Liao James C.
Published: December 2004

The death process of baculovirus‐infected insect cells was divided into two phases: a constant viability (or delay) phase characterized by a delay time (td) and a first‐order death phase characterized by a half‐life (t1/2). These two parameters were used in conjunction with the n‐target theory to classify the kinetics of cell death under various conditions, including different multiplicity of infection (MOI), host cell lines, virus types, incubation volumes, cell density and extracellular L(+)‐lactate and ammonium concentrations. Two groups of kinetic effects were found: one characterized by a constant number of hypothetical targets and the other by decreased numbers of hypothetical targets. The first group includes effects such as MOI, virus types, and host cell lines. The second includes the effects of environmental perturbations, such as incubation volume, cell density, and extracellular concentrations of L(+)‐lactate and ammonium. Although the underlying mechanisms of these effects are as yet unknown, the death kinetics of infected cells significantly affects the recombinant protein production. In general, foreign protein production does not correlate with the cell life after infection © 1993 John Wiley & Sons, Inc.
A model of biofilm detachment
Authors: Stewart Philip S.
Published: December 2004

A general mathematical framework for modeling biofilm detachment is presented. The approach is founded on a material balance on biomass that equates the detachment rate to the product of a detachment frequency and a detaching particle mass. The model provides a theoretical basis for deriving many of the empirical detachment rate expressions in common use and can thus lend some insight into their physical and biological significance. By allowing for variation in the detachment frequency with depth in the biofilm, the model permits derivation of detachment expressions that reflect a dependence on chemical or physiological gradients in the biofilm. Analysis of literature data sets from two different biofilm systems suggests, in both cases, that detachment is a growth‐associated phenomenon. © 1993 John Wiley & Sons, Inc.
Stability of plasmid vector plJ303 in Streptomyces lividans TK24 during laboratory‐scale fermentations
Authors: Wrigley‐Jones Carys A. , Richards Hilary , Thomas Colin R. , Ward John
Published: December 2004

Plasmid plJ303 stability in Streptomyces lividans cultures has been studied by measuring plasmid copy number under various growth conditions. An increase in mean plasmid copy number was normally seen during early rapid growth in both shaken culture and stirred vessel fermentations at 28°C. Maximum copy numbers were consistently attained in early stationary phase followed by a decline (of variable amount) upon further incubation. The imposition of environmental stress (high growth temperature, i.e., 37°C, and low dissolved oxygen tension, i.e., <5% air saturation) led to a plasmid copy number of zero and a 50% reduction, respectively. Interestingly, the relative proportions of plasmid topoisomers changed with time since progressively more supercoiled forms were observed throughout the stationary phase. Plasmid dimers were also observed in some cultures, and no evidence of structural plasmid instability was found. In general, this host‐vector system seemed remarkably stable under normal growth conditions. However, copious organic acid production by the host was observed and was thought to be undesirable for good heterologous gene expression of a secreted protein. © 1993 John Wiley & Sons, Inc.
Yield of poly‐D(‐)‐3‐hydroxybutyrate from various carbon sources: A theoretical study
Authors: Yamane Tsuneo
Published: December 2004

The theoretical yield of poly‐D(‐)‐3‐hydroxybutyrate (PHB) has been estimated from the biochemical pathway leading to PHB when a carbohydrate (glucose), a C1 compound (methanol), a C2 compound (acetic acid), or a C4 compound (butyric acid) is used as a carbon source. In estimating the yield, recycling (or regeneration) of NADP+/ (NADPH + H+) and NAD+ /(NADH + H+) have been taken into account. A special emphasis is made on te regeneration of NADPH, which is the coenzyme of acetoacetyl‐CoA reductase, one of three key enzymes involved in the biosynthesis of PHB. As a NADPH‐regenerating enzyme, glucose‐6‐phosphate dehydrogenase or isocitrate dehydrogenase is conceived. An equation which predicts the overall yield of PHB when non‐PHB residual biomass is actually formed has been derived as a function of both the theoretical yield and PHB content of the dry cell mass. The ratio of the overall yield to the theoretical yield is roughly proportional to the PHB content. © 1993 John Wiley & Sons, Inc.
Measurement of hydrodynamic shear by using a dissolved oxygen probe
Authors: Kim Ik‐Hwan , Cho Moo H. , Wang Shaw S.
Published: December 2004

When a dissolved oxygen (DO) probe is submerged in an air‐saturated cell culture medium the thickness of the liquid film that exists outside the membrane of a DO probe changes with hydrodynamic shear. The response of the DO probe thus varies with the hydrodynamic shear environment near the DO probe in cell culture reactors. The thickness of the liquid film was estimated by using a three‐layer model, which describes the flow of DO molecules through the liquid layer, the membrane, and the electrolyte, to the cathode of a DO probe. According to the three‐layer model, the current output of the DO probe was a strong function of thickness of the liquid film outside the membrane of the DO probe. A correlation between shear rates on the surface of the probe and the DO saturation reading was obtained by using two concentric cylinders with a rotating inner cylinder. This correlation was then used to characterize the local hydrodynamic shear environment in a cell culture reactor. © 1993 John Wiley & Sons, Inc.
Formation of microparticulate protein powder using a supercritical fluid antisolvent
Authors: Yeo Sang‐Do , Lim Gio‐Bin , Debendetti Pablo G. , Bernstein Howard
Published: December 2004

Gas antisolvent (GAS) expansion of dimethylsulfoxide (DMSO) and N,N‐dimethylformamide (DMFA) solutions with supercritical carbon dioxide was used to produce biologically active powders of insulin. Powders with 90% of the particles smaller than 4 μm and 10% smaller than 1 μm were obtained under all conditions tested when the process was operated continuously, with small liquid droplets sprayed into a flowing supercritical continuum. Slow pressurization of the stagnant protein solution resulted in larger particles. In vivo tests on rats revealed no differences between the biological activity of processed and unprocessed insulin, GAS processing of organic solution appears to be a reliable and effective method for the production of dry, biologically active microparticulate powders of peptides and proteins. © 1993 John Wiley & Sons, Inc.
Startup of anaerobic fluidized bed reactors with acetic acid as the substrate
Authors: Hsu Yen , Shieh Wen K.
Published: December 2004

The startup of anaerobic fluidized bed reactors, which use Manville R‐633 beads as the growth support media, acetate enriched bacterial culture as the inoculum, and acetic acid as the sole substrate, is studied. Tow startup strategies are evaluated: one based on maximum and stable substrate utilization and another based on maximum substrate loading controlled by reactor pH. The startup process is characterized using a number of operational parameters.

The reactors again excellent total organic carbon (TOC) removal (i.e., > 97% at a feed concentration of 5000 mg TOC/L) and stable methane production (i.e., 0.90 L CH4/g TOC, where TOCr is TOC removed) at a early stage of the startup process, regardless of the strategies applied. The loading can be increased rapidly without the danger of being overloaded. Significant losses of growth support media and biomass caused by gas effervescence at higher loadings limits the maximum loading that can be safely applied during startup process.

A high reactor immobilized biomass inventory is achievable using the porous growth support media (e.g., Manville 633 beads). A rapid increase in loading creates a substrate rich environment that yields more viable reactor biomass. Both substrate utilization rate (batch and continuous) and immobilized biomass inventory stabilize concomitantly at the late stage of the startup process, indicating the attainment of steady‐state conditions in reactors. Therefore, they are better parameters that TOC removal and methane production for characterizing the entire startup process of aerobic fluidized bed reactor.

The strategy based on maximum substrate loading controlled by reactor pH significantly shortens the startup time. In this case, the reactor attains steady‐state conditions approximately 140 days after startup. On the other hand, a startup time of 200 days is required when the strategy based maximum substrate utilization is adopted. © 1993 John Wiley & Sons, Inc.
Application of gravitational sedimentation to efficient cellular recycling in continuous alcoholic fermentation
Authors: Maia Amazile B. R. A. , Nelson David Lee
Published: December 2004

A mathematical model for the sedimentation velocity in an inclined parallel plate sedimenter is proposed. The parameters of the alcoholic fermentation broth (cell density of Saccharomyces cerevisiae, density of the fermentation medium, viscosity of the broth at various alcohol and biomass contents) were determined experimentally. The sedimentation velocities were predicted under the various operational conditions and parameters, both of the broth (the alcohol concentration and cell content) and the sedimenter prototype (length, distance between the plates, and slope). The proposed model for the sedimentation velocity presented a good correlation with the experimental results of continuous sedimentation. These sedimenter prototypes were assembled and tested for efficiency of separation of yeast cell under conditions considered for interest for continuous alcoholic fermentation. A selective filter for the overflow composed of calcium alginate gel improved operation. A high operational stability, high separation efficiency (over 98%), and adequate settler residence times (about 20 min) were attained. The operational results permitted the operation of continuous alcoholic fermentation with cellular recycling effected exclusively by gravitational sedimentation, this characterizing a process of enormous industrial interest because of the operational simplicity and low operational and maintenance costs. © 1993 John Wiley & Sons, Inc.
Comparison of substrate utilization and growth kinetics between immobilized and suspended Pseudomonas cells
Authors: Shreve Gina S. , Vogel Timothy M.
Published: December 2004

A methodology is described for measurement if immobilized and suspended cell growth and substrate utilization kinetics parameters. Substrate utilization and growth kinetics were compared between immobilized and suspended cells for toluene degrading Pseudomonas strains K3‐2 and 2,4‐dichlorophenoxyacetic acid (2,4‐D) degrading strain DBO131(pR0101), respectively. Kinetic parameters were estimated using nonlinear parameter estimation methods and compared between the immobilized and suspended Pseudomonas cells to determine the effect of immobilization on cellular growth and substrate utilization. Factors influencing the experimental design included calculated oxygen flux rates, primary carbon substrate flux rates, and shear stresses on the immobilize cell. Statistical interpretation of the cellular reaction rate parameters indicates that only the growth kinetics of the toluene system were significantly altered upon immobilization. Substrate utilization kinetics remained unchanged upon immobilization. The substrate growth associated half‐saturation constant (Kg) for the toluene system increased by 30‐fold and the maximum specific growth rate (μmax) decreased by 2‐fold upon immobilization. Implication of these results for experimental determination of cellular kinetic parameters and for immobilization cell bioreactors design are discussed. © 1993 John Wiley & Sons, Inc.
Toward a control of lignin and manganese peroxidases hypersecretion by Phanerochaete chrysosporium in agitated vessels: Evidence of the superiority of pneumatic bioreactors on mechanically agitated bioreactors
Authors: Bonnarme P. , Delattre M. , Drouet H. , Corrieu G. , Asther M.
Published: December 2004

Phanerochaete chrysosporium and cultivated both mechanically agitated and pneumatic bioreactors. In the pneumatic devices, the yields of lignin and manganese peroxidases as well as extracellular protein, were considerably increased as compared with mechanically agitated bioreactors. Lignin peroxidase and manganese peroxidase activities as high as 4500 U · L−1 and 1812 U · L−1 respectively, were produced in an airlift bioreactor. By using enzyme markers, the secretion pathway and the respiration were shown to be dramatically activated in pneumatic bioreactors. The general metabolism of the fungus, when cultivated in the conventional fermentors, is oriented toward the synthesis of biomass at the expense of the synthesis of peroxidases. The use of pneumatic devices for the production of extracellular peroxidases by P. chrysosporium, avoids shear effects due to turbine agitator in the conventional fermentors, and provides a good example for the production of shear‐sensitive metabolites. © 1993 John Wiley & Sons, Inc.
Development of an enzyme membrane reactor for treatment of cyanide‐containing wastewaters from the food industry
Authors: Basheer S. , Kut Ö. M. , Prenosil J. E. , Bourne J. R.
Published: December 2004

Cyanidase, an immobilized enzyme preparation for hydrolyzing cyanide to ammonia and formate, was applied for the treatment of cyanide‐containing waste waters from the food industry. Apricot seed extract was chosen as a model effluent. The enzymatic hydrolysis of pure amygdalin, the main cyanogenic glycoside in the extract, and the degradation of the cyanide formed was investigated and compared with the behavior of the real extract in a batch slurry reactor. A diffusional‐type, flat‐membrane reactor with immobilized cyanidase was developed, where the enzyme is effectively protected from adverse effects of high molecular components contained in the extract. For monitoring continuous‐membrane reactor operation, a new unsegmented ammonia measurement system was developed and applied. In continuous operation the cyanidase retained its original activity for more than 400 hours on steam. © 1993 John Wiley & Sons, Inc.
Enzymatic activity under tangential flow conditions of photochemically grafted membranes containing immobilized catalase
Authors: Selli Elena , D'Ambrosio Andrea , Bellobono Ignazio Renato
Published: December 2004

Catalase has been immobilized within sandwich membranes prepared by the photoinduced grafting of an epoxy‐diacrylate prepolymer onto commercial asymmetric cellulose membranes. The enzymatic activity of the membrane composite of hydrogen peroxide decomposition has been studied in a recirculation apparatus under tangential flow conditions without ultrafiltration. The enzymatic membranes were exposed to very low mechanical stresses and showed a very good catalytic performance and durability. Initial reaction rates, measured at 25°C as a function of both substrate concentration and enzyme amount immobilized per unit membrane surface, indicate that the mechanism of action of catalase is not altered after immobilization, although substrate diffusion through the original thin layer of membranes may become rate controlling. © 1993 John Wiley & Sons, Inc.
Enhancement of recombinant protein synthesis and stability via coordinated amino acid addition
Authors: Ramérez Delia M. , Bentley William E.
Published: December 2004

In this work, effective feeding schemes that would minimize stress responses to cloned‐protein overexpression are investigated. The cloned‐protein (chloramphenicolacetyl‐transferase, CAT) contains a high aromatic amino acid content, most notably a high phenylalanine content. Experiments performed on Escherichia coli RR1 [pBR329] (constitutive promoter) and E. coli JM105 [pSH101] (inducible promoter) demonstrated that phenylalanine addition increases the rate of synthesis and yield of CAT. A previous study correlating inducer strength with CAT expression in E. coli JM105 [pSH101] indicated that the highest expression rate was accompanied by the highest apparent rate of protein degradation. In this work, the combined addition of isopropyl‐β‐D‐thiogalactopyranoside (IPTG) and phenylalanine at intermediate levels resulted in substantial increase of CAT synthesis and partial reduction of protein degradation. Furthermore, transmission electron micrographs verified the absence of inclusion bodies, which, along with proteases, were suspected to reduce protein activity. The research demonstrates that significant enhancement in production and stability of heterologous proteins is possible by designing feeding strategies that incorporate knowledge of the interaction between primary cellular metabolism and foreign protein expression. © 1993 John Wiley & Sons, Inc.
Dynamics of phenol degradation by Pseudomonas putida
Authors: Allsop P. J. , Chisti Y. , Moo‐Young M. , Sullivan G. R.
Published: December 2004

Pure cultures of Pseudomonas putida (ATCC 17484) were grown in continuous culture on phenol at dilution rates of 0.074–0.085 h−1 and subjected to step increases in phenol feed concentration. Three distinct patterns of dynamic response were obtained depending on the size of the step change used: low level, moderate level, or high level. During low level responses no accumulations of phenol or non‐phenol, non‐glucose‐dissolved organic carbon, DOC(NGP), were observed. Moderate level responses were characterized by the transient accumulation of DOC(NGP) with a significant delay prior to phenol leakage. High level responses demonstrated a rapid onset of phenol leakage and no apparent accumulations of DOC(NGP). The addition of phenol to a continuous culture of the same organism on glucose did not result in transient DOC(NGP) accumulations, although transient phenol levels exceeded 90 mg l−1. These results were consistent with intermediate metabolite production during phenol step tests coupled with substrate‐inhibited phenol uptake and suggested that traditional kinetic models based on the Haldane equation may be inadequate for describing the dynamics of phenol degrading systems. © 1993 John Wiley & Sons, Inc.
Criteria to assess when biodegradation is kinetically limited by intraparticle diffusion and sorption
Authors: Chung Gui‐Yung , McCoy Ben J. , Scow Kate M.
Published: December 2004

To determine when intraparticle diffusion and sorption can influence the rate of biodegradation, we consider the biodegradation of a pollutant diffusing into or out of porous aggregates suspended in a liquid medium, where the reactant is metabolized by bacteria. The pollutant that diffuses into the aggregates obeys a sorption–desorption equilibrium isotherm at sites on inner pore surfaces. The governing partial differential equations for the transient process describe (a) the local equilibrium sorption–desorption and the diffusion of the pollutant in the porous aggregate, (b) the mass transfer of the pollutant from the external surface of the spherical aggregates to the reaction medium, and (c) the biodegradation of the pollutant in the external medium. Illustrative calculations are presented for a linear sorption calculations are presented for a linear sorption isotherm and first‐order biodegradation kinetics. A dimensionless group, comprised of the diffusion coefficient, biodegradation rate coefficient, aggregate characteristics length (radius), and adsorption capacity, serves as a criterion for determining when intraparticle diffusion can be ignored. The model provides a realistic description of experimental data for biodegradation of a pollutant subject to intraparticle diffusion and sorption. © 1993 John Wiley & Sons, Inc.
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

Phosphorus‐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

Effective 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

Biomass 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

An 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

The 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

A 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

Concanavalin 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

Basic 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

In 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

The 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

Reduction 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

Determination 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

The 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

In 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

The 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

The 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

Two‐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.