摘要:

AbstractFlux and retention of 0.1%w/w aqueous solutions of several proteins [lysozyme, pepsin, bovine serum albumin (BSA), lipase, and γ‐globulin] with molecular weights of 14.6, 36, 67, 801 and 150 kDa are studied when they are tangentially filtered, with transmembrane pressure differences until 1 MPa and circulation velocities in the re‐tentate loop from 0.04 to 1.98 m/s (laminar regime), through two asymmetric polysulfone commercial membranes (E‐100 with a nominal pore size of 0.01 μm and E‐500 with a nominal pore size of 0.04 μm). Results are analyzed with the film theory for the concentration‐polarization phenomenon, obtaining the mass transfer coefficient along with the apparent and true retention coefficients for the cell used, as a function of the feed circulation velocity and the molecular weight of the solute. The standard retention curves lead to pore size distributions differing from the nominal ones. These differences can be attributed to the modifications of the membranes when they are in operational conditions, probably due to protein adsorption. © 1995 John Wi

ISSN:0006-3592    

DOI:10.1002/bit.260470602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe specific growth rate of the biomass, a very important parameter of almost every fermentation process, cannot be measured directly or estimated from related variables, as the concentrations of biomass, substrates, or products, due to the lack of reliable and cheap sensors. In this article a stable adaptive estimator of the specific growth rate is designed for those aerobic processes where the measurement of the oxygen uptake rate is available on‐line. This particular approach can be applied also for other reaction rates if the model of the process satisfies some very general assumptions, which make the dynamics of the measured reaction rate a nonlinear function only of two unknown parameters, the specific growth rate and its time derivative. With respect to a previous similar approach, the new estimator has one additional parameter and a different nonlinear structure. From the analysis of the dynamics of the estimation error, a tuning criterion is derived, by which the two different algorithms can be compared under similar conditions. Simulation results show a good performance of both estimators for various kind of processes and disturbances. © 1995 John Wiley&Sons, I

ISSN:0006-3592    

DOI:10.1002/bit.260470603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe aim of the present work is to study the sequential adsorption of F(ab′)2and bovine serum albumin (BSA) molecules adsorbed onto positively and negatively charged polystyrene latexes. Cationic and anionic latexes were prepared by emulsifier‐free emulsion polymerization. Adsorptions of F(ab′)2on both latexes at a low ionic strength and different pHs were performed. The cationic latex showed a higher adsorption of F (ab′)2molecules over a range of pH, which could be due to the formation of multilayers. Sequential adsorption of anti‐CRP F(ab′)2and monomeric BSA were performed at two different pre‐adsorbed F(ab′)2amounts on both types of latex. Displacement of F(ab′)2occurred only when the preadsorbed amounts were larger than a certain critical value, which depends on the adsorption pH. A greater displacement of larger preadsorbed amounts might be the result of a weaker contact between the protein molecules and the polystyrene surface. The displacement of F(ab′)2previously adsorbed onto both latexes occurred due to pH changes, an increase of ionic strength and the presence of BSA molecules. The effect caused by these three factors was studied independently. The main factors in the desorption of F(ab′)2on the anionic latex are the changes in pH and ionic strength, whereas on the cationic latex the desorption is mainly caused by the increase of the ionic strength and the presence of BSA. The colloidal stability of the immunotatex was improved by BSA adsorption, especially on cationic latex. © 199

ISSN:0006-3592    

DOI:10.1002/bit.260470604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of oscillating dissolved oxygen (DO) concentration on the metabolism of a clonal isolate of theSpodoptera frugiperdaIPLB‐Sf21‐AE insect cell line was investigated. Specifically, the effect on cell growth, re‐ combinant protein synthesis, glucose and glutamine consumption, and lactate accumulation was determined. Prior to conducting the oscillating DO experiments, it was found that the DO concentration could be reduced to 15% air saturation without adversely affecting the growth rate. Under these conditions, glucose and glutamine became depleted as the maximum cell density was reached. The introduction of DO oscillations, that is, cycles consisting of 30 min at 15% DO followed by 30 min of anoxia, significantly altered cell metabolism, including inhibition of cell growth and recombinant protein synthesis. The effect of DO oscillations on glucose consumption was dependent on the experimental conditions. Glucose exhaustion occurred when the DO oscillations contained either an “apparent” anoxia period (nitrogen sparging discontinued upon reaching 0% DO) without pH control or a “true” anoxia period (nitrogen sparging continued throughout anoxia period) with pH control. Glucose consumption was significantly decreased, however, when the cells were exposed to a “true” anoxia period without pH control, that is, low pH inhibited glucose utilization. Glutamine uptake was not significantly affected by DO oscillations. Lactate only accumulated in the oscillating DO runs, a finding consistent with previous results demonstrating that significant lactate accumulation only occurs under DO‐limited conditions. © 1995

ISSN:0006-3592    

DOI:10.1002/bit.260470605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe linear relation between the pH control reagent addition rate, the net conversion rates of metabolites, the carbon dioxide mass transfer rate and the feed rates is developed and shown to have the same form for batch, fed‐batch, and continuous reactors, regardless of the number of feeds. The magnitudes of various biological and solution chemistry effects on the pH control reagent addition rate are estimated to be negligible, facilitating the use of the pH control reagent addition rate as a straightforward indicator of primary metabolism. Finally, application of the linear relation, termed the abiotic proton balance, is discussed for a number of fermentation processes. © 1995 John Wiley&Sons, I

ISSN:0006-3592    

DOI:10.1002/bit.260470606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe kinetics of biomass accumulation, nutrient uptake and taxol production of Taxus baccata cell suspensions were examined in three bioreactor configurations, viz. 250‐mL Erienmeyerflasks, 1‐L working volume pneumatically mixed (PMB), and stirred tank (STB) bioreactors. Qualitatively similar kinetics were observed in all three bioreactor types. Biomass accumulation and specific nutrient uptake rates exhibited biphasic characteristics. Carbohydrate uptake and biomass accumulation substantially ceased when phosphate was depleted from the medium. Phosphate was identified as a possible growth‐limiting nutrient. Taxol accumulated exclusively in the second phase of growth. A maximum taxol concentration of 1.5 mg/L was obtained in the PMB which was fivefold greater than that obtained in the Erienmeyer flasks and the STB, but the relative kinetics of taxol production was the same in all three reactor types. Biomass yields were calculated from the kinetic data and a stoichiometry for biomass formation was evaluated. The similarity of kinetics in the three bioreactor configurations suggests that taxol production byT. baccatacell suspensions is amenable to scateup. © 1995 John Wiley&Son

ISSN:0006-3592    

DOI:10.1002/bit.260470607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractImmobilization of conidiospores ofPhanerochaete chrysosporiumby adhesion was investigated in static and flow conditions on flat and on porous supports. Reducing the electrostatic repulsion between the spores and the support by adsorption of polycations on the support allows a better adhesion efficiency and a higher density of adhering spores and does not affect germination and growth. Formation of spore aggregates either in the suspension (high ionic strength) or on the support tends to decrease the surface coverage and to give an inhomogeneous distribution of adhering spores due to detachment of aggregates. The density of spores adhering from a flowing suspension is lower as compared with static conditions and does not exceed about 2% of surface coverage; this is due to the influence of tangential forces, to the short contact time with the surface, and to perturbation of the hydrodynamics along the surface by the previously immobilized spores. Obtaining a high coverage of the support by immobilized spores requires the absence of a tangential motion. © 1995 John Wiley&Sons, Inc

ISSN:0006-3592    

DOI:10.1002/bit.260470608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effects of various medium sterilization conditions on fermentations of a recombinant, acidic fibroblast growth factor (aFGF) producingEscherichia colihave been studied. Changes in the medium resulting from sterilization were monitored by pH and absorption spectra. This simple experiment provided excellent data for the demonstration of the usefulness of comparative reasoning tools in order to evaluate the effect of sterilization on fermentation performance. The time profiles of the main parameters (e.g., carbon dioxide evolution rate, dissolved oxygen, pH, and aFGF productivity) were simplified into piecewise contiguous linear segments, each of which was sequentially numbered. The length, position, and slope of each tine were then characterized. Application of the comparative reasoning tools confirmed that separate sterilization of the glucose was necessary for the success of the process, despite adding to the cost and complexity. The comparative data analysis also showed that scaleup with longer sterilization holding and cooling times would not be detrimental to aFGF production. © 1995 John Wiley&Sons, Inc

ISSN:0006-3592    

DOI:10.1002/bit.260470609

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractTo alleviate plasmid instability and to prolong the production phase of subtilisin, integrable plasmid and spore mutants are used. Compared with batch‐type shake flask cultures, spore mutants' ability to produce subtilisin can be well pronounced in fed‐batch and continuous cultures. Hence, the two culture methods make it possible to identify the peculiar characteristics of the spore mutants unobtainable in batch culture. Spore mutants can enhance subtilisin productivity and prolong subtilisin production time in fed‐batch culture as well as enable us to use very low dilution rates (<0.1 h−1) without losing productivity in continuous culture, thereby improving the conversion yield of the nitrogen source. At 0.05 h−1thespollGmutant ofBacillus subtilis DB104(ΔnprΔapr) (Emr)spollG(Bimr)::pMK101(Cmr) showed a subtilisin yield about ten times higher than that from wild‐typeDB104(ΔnprΔapr)::pMK101(Cmr). © 1995 John

ISSN:0006-3592    

DOI:10.1002/bit.260470610

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractA packed bed biofilm reactor inoculated with pure culturePseudomonas aeruginosawas run under high substrate loading and constant flow rate conditions. The 3.1‐cm‐diameter cylindrical reactor was 5 cm in length and packed with 1‐mm glass beads. Daily observations of biofilm thickness, influent and effluent glucose substrate concentration, and effluent dissolved and total organic carbon were made during the 13‐day experiment. Biofilm thickness appeared to rech quasi‐steady‐state condition after 10 days. A published biofilm process simulation program (AQUASIM) was used to analyze experimental data. Comparison of observed and simulated variables revealed three distinct phases of biofilm accumulation during the experiment: an initial phase, a growth phase, and a mature biofilm phase. Different combinations of biofilm and mass transport process variables were found to be important during each phase. Biofilm detachment was highly correlated with shear at the biofilm surface during all three phases of biofilm development. © 1995 John Wil

ISSN:0006-3592    

DOI:10.1002/bit.260470611

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY