ISSN:0006-3592    

DOI:10.1002/bit.260430102

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

年代:1994

数据来源: WILEY

摘要:

AbstractMeasurements provide the basis for process monitoring and control as well as for model development and validation. Systematic approaches to increase the accuracy and credibility of the empirical data set are therefore of great value. In (bio)chemical conversions, linear conservation relations such as the balance equations for charge, enthalpy, and/or chemical elements, can be employed to relate conversion rates. In a pactical situation, some of these rates will be measured (in effect, be calculated directly from primary measurements of, e.g., concentrations and flow rates), as others can or cannot be calculated from the measured ones. When certain measured rates can also be calculated from other measured rates, the set of equations, the accuracy and credibility of the measured rates can indeed be improved by, respectively, balancing and gross error diagnosis. The balanced conversion rates are more accurate, and form a consistent set of data, which is more suitable for further application (e.g., to calculate nonmeasured rates) than the raw measurements. Such an approach has drawn attention in previous studies. The current study deals mainly with the problem of mathematically classifying the conversion rates into balanceable and calculable rates, given the subset of measured rates. The significance of this problem is illustrated with some examples. It is shown that a simple matrix equation can be derived that contains the vector of measured conversion rates and the redundancy matrixR. MatrixRplays a predominant role in the classification problem. In supplementary articles, significance of the redundancy matrixRfor an improved gross error diagnosis approach will be shown. In addition, efficient equations have been derived to calculate the balanceable and/or calculable rates. The method is completely based on matrix algebra (principally different from the graph‐theoretical approach), and it is easily implemented into a computer program. © 1994 John Wiley&Sons, I

ISSN:0006-3592    

DOI:10.1002/bit.260430103

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

年代:1994

数据来源: WILEY

摘要:

AbstractConservation equations derived from elemental balances, heat balances, and metabolic stoichiometry, can be used to constrain the values of conversion rates of relevant components. In the present work, their use will be discussed for detection and localization of significant errors of the following types:1.At least one of the primary measurements has a significant error (gross measurement error).2.The system definition is incorrect: a componenta.is not included in the system description.b.has a composition different from that specified.3.The specified variances are too small, resulting in a too‐sensitive test.The error diagnosis technique presented here, is based on the following: given the conservation equations, for each set of measured rates, a vector of residuals of these equations can be constructed, of which the direction is related to the error source, as its length is a measure of the error size. The similarity of the directions of such a residual vector and certaincompare vectors, each corresponding to a specific error source, is considered in a statistical test. If two compare vectors that result from different error sources have (almost) the same direction, errors of these types cannot be distinguished from each other. For each possible error in the primary measurements of flows and concentrations, the compare vector can be constructed a priori, thus allowing analysis beforehand, which errors can be observed. Therefore, the detectability of certain errors likely to occur can be insured by selecting a proper measurement set. The possibility of performing this analysis before experiments are carried out is an important advantage, providing a profound understanding of the detectability of errors. The characteristics of the method with respect to diagnosis of simultaneous errors and error size estimation are discussed and compared to those of the serial elimination method and the serial compensation strategy, published elsewhere. © 1994 John Wiley&Sons, I

ISSN:0006-3592    

DOI:10.1002/bit.260430104

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

年代:1994

数据来源: WILEY

摘要:

AbstractA new group‐specific affinity membrane using metal chelates as ligands and inorganic glass hollow fiber microfiltration membranes as support matrices is developed and tested. The study focused on developing the optimum activation and coupling procedures to bind the chelating agent (iminodiacetic acid, IDA) to the surface of the microporous glass hollow fiber membrane and testing the resultant affinity membrane. Starting with three different glass surfaces, five modification reactions were evaluated. All the modified “active surfaces” were first tested for their protein adsorptive properties in batch mode with suspended microporous glass grains using model proteins with known binding characteristics with Cu–IDA systems. The metal loading capacities of the surfaces exhibiting favorable fractionation were then measured by atomic absorption spectroscopy.The results were compared with the results obtained with a commercial material used in immobilized metal affinity column chromatography. The protein binding characteristics of the hollow fiber affinity membranes were also evaluated under conditions of convective flow. This was performed by flowing single solute protein solutions through the microporous membrane at different flow rates. These results were then used to estimate the optimum loading and elution times for the process. A mathematical model incorporating radial diffusion was solved using a finite difference discretization method. Comparison between model predictions and experimental results was performed for four different proteins at one flow rate. These results suggested that the kinetics of adsorption was concentration dependent. Finally, the hollow fiber affinity membranes were challenged with two component mixtures to test their ability to fractionate mixed protein solutions. Efficient separation and good purity were obtained.The results presented here represent the development of a new fast flow affinity membrane process–immobilized metal affinity membranes (IMAM). © 1994 John Wiley

ISSN:0006-3592    

DOI:10.1002/bit.260430105

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

年代:1994

数据来源: WILEY

摘要:

AbstractIt is proposed that when cells are either attached to, or very near, a rupturing bubble, the hydrodynamic forces associated with the rupture are sufficient to kill the cells. Four types of experiments were conducted to quantify the number and location of these killed cells. We determined: (1) the number of cells killed as a result of a single, 3.5‐mm bubble rupture; (2) the number and viability of cells in the upward jet that results when a bubble ruptures; (3) the number of cells on the bubble film; and (4) the fate of cells attached to the bubble film after film rupture. All experiments were conducted withSpodoptera frugiperda(SF‐9) insect cells, in TNM‐FH and SFML medium, with and without Pluronic F‐68. Experiments indicate that approximately 1050 cells are killed per single, 3.5‐mm bubble rupture in TNM‐FH medium and approximately the same number of dead cells are present in the upward jet. It was also observed that the concentration of cells in this upward jet is higher than the cell suspension in TNM‐FH medium without Pluronic F‐68 by a factor of two. It is believed that this higher concentration is the result of cells adhering to the bubble interface. These cells are swept up into the upward jet during the bubble rupture process. Finally, it is suggested that a thin layer around the bubble containing these absorbed cells is the “hypothetical killing volume” presented by other researchers. © 1994

ISSN:0006-3592    

DOI:10.1002/bit.260430106

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe enhancement of the overall disruption of a native strain ofCandida utilis(ATCC 9226) was studied using a combination of two methods, namely, pretreatment in the form of partial enzymatic lysis by Zymolyase followed by mechanical disruption in a Microfluidizer high‐pressure homogenizer. The cells were grown in both batch and continuous cultures to examine the effect of specific growth rate on disruption. Cell suspensions ranging in concentration from 7 to 120 g DW/L were disrupted with and without enzymatic pretreatment. For yeast grown in batch culture, final total disruption obtained using the combined protocol approached 95% with four passes at a pressure of 95 MPa, as compared with only 65% disruption using only mechanical homogenization. A modified model was developed to predict the fraction disrupted by the enzymatic pretreatment‐mechanical homogenization two‐stage process. Predicted disruptions agreed favorably with experimental observations (maximum deviation of 20%) over a wide range of operating conditions. © 1994 John Wiley&Son

ISSN:0006-3592    

DOI:10.1002/bit.260430107

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

年代:1994

数据来源: WILEY

摘要:

AbstractA means of rapidly renaturing denatured protein was devised and evaluated. Three liquids were laminarly layered in a centrifuge tube, in which two solutions sandwiched liquid paraffin so as to form a pseudolipid bilayer. Denatured and aggregted protein placed on the upper surface of liquid paraffin was renatured as it passed through liquid‐paraffin layer into the renaturation buffer during the centrifugation. The aggregated and denatured protein selectively passed through the liquid‐paraffin layer, whereas other solutions, such as chaotropic agents or organic solvent, could not. This means that a rapid dilution condition favorable for protein renaturation was realized in a small scale. Aggregated and denatured BSA and ribonuclease A were renatured and resolubilized as they passed through the liquid‐paraffin layer into an appropriate renaturation buffer solution. This method was also applied to the rapid heme reconstitution of myoglobin from Feprotoporphyrin IX to Zn‐protoporphyrin IX. © 1994 John Wiley&S

ISSN:0006-3592    

DOI:10.1002/bit.260430108

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

年代:1994

数据来源: WILEY

摘要:

AbstractImprovement of stereoselective resolution of racemic Naproxen, 2‐(6‐methoxy‐2‐naphthyl)propionic acid, was attempted with esterifcation reaction byCandida cylindracealipase. By carefully selecting the organic medium, a 72‐time enhancement of yield of the desired S‐ester was achieved. The optimal reaction temperature was approximately 53°C, and an alcohol concentration between 20 mMand 40 mMin an 80% (v/v) isooctane and 20% (v/v) toluene mixture was found. © 1994 John Wi

ISSN:0006-3592    

DOI:10.1002/bit.260430109

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

年代:1994

数据来源: WILEY

摘要:

AbstractFermentations of the yeastSaccharomyces cerevisiaewere carried out in a 90 to 250‐L working volume concentric tube airlift fermentor. Measurements of liquid circulation velocity, gas hold‐up, and liquid mixing were made under varying conditions of gas flowrate, vessel height, and top‐section size. Both liquid circulation velocity and mixing time increased with vessel height. Liquid velocity varied approximately in proportion to the square root of column height, supporting a theoretically based relationship. The effect of vessel height on gas hold‐up was negligible. The height of the top‐section had a significant effect on liquid mixing. Mixing time decreased with increasing size of the top‐section up to a critical height. As the top‐section was expanded beyond this height, little improvement in mixing was seen. This indicated the presence of a two‐zone flow pattern in the top‐section. Liquid velocity and gas hold‐up were essentially independent of top‐section height. © 199

ISSN:0006-3592    

DOI:10.1002/bit.260430110

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

年代:1994

数据来源: WILEY

摘要:

AbstractA search was undertaken for osmoprotective compounds for mouse hybridoma cell line 6H11 grown in culture. When the osmolality of the growth medium was increased above the normal osmolality of 330 mOsmol/kg, growth rates were decreased in a dose‐dependent fashion, reaching zero when the osmolality of the medium reached approx. 435 mOsmol/kg through the addition of KCl (60 mM), or 510 mOsmol/kg through the addition of NaCl (100 mM), or sucrose (175 mM). For NaCl or sucrose‐stressed cultures, the inclusion of glycine betaine, sarcosine, proline, glycine, or asparagine in the growth medium gave a moderate to strong osmoprotective effect, measured as the ability of these compounds to enhance cell growth rates under hyperosmotic conditions. Inclusion of dimethylglycine may also give a strong osmoprotective effect under these stress conditions.In KCl‐stressed cell cultures, addition of glycine betaine, sarcosine, or dimethylglycine gave strong osmoprotective effects. Of 38 compounds tested during NaCl stress, 7 gave weak osmoprotective effects and 25 gave no osmoprotective effect. The osmoprotective compounds accumulated inside the stressed cells. Accumulation was completed after 4 to 8 h, reaching intracellular concentrations of approx. 0.27 pmol/cell, or 0.15M, in NaCl stressed cells (100 mMNaCl added).Glycine betaine, dimethylglycine, and sarcosine accumulation was observed only when these protectants were included in the medium. For all osmoprotectants, a growth medium concentration between 5 and 30 mMgave the maximal protective effect, with the exception of dimethylglycine, for which the optimum concentration was approx. 65 mM. Osmoprotective effects obtained with glycine, sarcosine, dimethylglycine, and glycine betaine, indicate that the more methylated compounds are the most effective protectants.The cellular content of glycine betaine and the glycine betaine uptake rate increased with medium osmolality in a linear fashion. Glycine betaine uptake was described by a model comprising a saturable component obeying Michaelis–Menten kinetics and a nonsaturable component.KmandVmaxfor glycine betaine uptake were determined at 420 mOsmol/kg (50 mMNaCl added) and 510 mOsmol/kg (100 mMNaCl added). AKmvalue of approx. 2.5 mMwas obtained at both medium osmolalities, whileVmaxincreased from 0.010 pmol/cell · h to 0.018 pmol/cell · h as the osmolality of the growth medium was increased, indicating an effect of medium osmolality on the maximal rate of transport rather than on the affinity of the transporters for glycine betaine. Hybridoma cells were not able to utilize the glycine betaine precursors choline or glycine betaine aldehyde for osmoprotection, suggesting that the cells lack part, or all, of the choline–glycine betaine pathway or the appropriate uptake mechanism.The uptake rate for glycine in NaCl‐stressed hybridoma cells was approx. four times higher than the uptake rate for glycine betaine. Furthermore, if equimolar amounts of glycine betaine, glycine, sarcosine, and proline were simultaneously added to NaCl‐stressed cell cultures, the intracellular concentrations of glycine, proline, and sarcosine were significantly higher than the concentration of glycine betaine.A 40% increase in hybridoma cell volume was observed when the growth medium osmolality was increased from 300 to 520 mOsmol/kg. © 1994 John

ISSN:0006-3592    

DOI:10.1002/bit.260430111

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

年代:1994

数据来源: WILEY