摘要:

AbstractProcess scaleup for stirred‐tank animal cell cultures such as suspension and microcarrier cultures often begins at the bench scale in small spinner vessels. In order to initiate process development under the proper conditions, it is essential to know the physical conditions under which the cells are grown. In this article, power inputs and surface oxygen transfer rates to culture medium in 500‐mL Corning spinner vessels were determined as a function of the impeller geometry, impeller height, and agitation speed. The results obtained indicate that power dissipation dependency differs from literature correlations and may compromise scale up at constant power input from these vessels. These results are of general utility to researchers using small‐scale ve

ISSN:0006-3592    

DOI:10.1002/bit.260340902

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

年代:1989

数据来源: WILEY

摘要:

AbstractProtein localization inSaccharomyces cerevisiaewas studied with two plasmid systems used as a model: one containing theSUC2structural gene fused with theMFα1 (α‐factor) promoter and signal‐sequence, the other containing the entireSUC2gene. Special emphasis was placed on the effect of promoter/signal‐sequence (SUC2vs.MFα1) on the efficiency of invertase transport. TheMFα 1 andSUC2signal sequences were capable of transporting, respectively, 83% and 77% of cloned invertase out of the cytoplasm. However, theSUC2promoter was easier to control since a six‐fold enhancement of the transported invertase activity associated with derepression was achieved in response to a glucose concentration change from 10 to 2 g/L Cloning on a multicopy plasmid resulted in a four‐fold increase in total specific invertase activity over the wild type yeast strain (which harbors a single copy of theSUC2gene on the chromosome), whereas the chromosomal site was more efficient for invertase localization yielding over 90% of the invertase transported out of the cytoplasm. Transient experiments done with theSUC2signal‐sequence‐containing plasmid showed that the specific invertase activity in the periplasmic space reached a maximum three hours after derepression, then decreased very slowly with an accompanying gradual increase in invertase activity in

ISSN:0006-3592    

DOI:10.1002/bit.260340903

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

年代:1989

数据来源: WILEY

摘要:

AbstractA method for the simultaneous extraction of oil and proteins from vegetable meals is presented. The method uses hydrocarbon reverse micelles, so that the oil is extracted directly into the hydrocarbon phase and the proteins are solubilized in the water pools of the reverse micelles. The surfactant used is bis (2‐ethylhexyl) sodium sulfosuccinate (AOT) in isooctane at variablew0values (w0measures the amount of water in the system, wherew0= [H2O]/[AOT]). A comparison with the usual extraction methods is offered. It is shown that with the micelle system the extraction of oil is as large as with the usual methods, and it is independent ofw0. However the amount and type of proteins extracted depends strongly onw0. Atw0values below 6, no protein and only low molecular weight compounds (i.e. chlorogenic acid) are extracted, at larger water content (i.e. by increasing the dimension of the micelle water pool), also proteins are solubilized in a significant amount and with a molecular weight which increases by increasingW0. The protein solubilized in the microemulsion system can be recovered into an aqueous phase with a back‐transfer s

ISSN:0006-3592    

DOI:10.1002/bit.260340904

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe dynamic gassing‐out method using nitrogen for gas–liquidKLameasurements has been modified so that gassing‐out is performed with air and gassing‐in with oxygen‐enriched air. This new method was proven theoretically valid for use in inert model systems and in actual fermentation systems. TheKLavalues were measured in a 1‐m‐high bubble column and compared with those obtained from the traditional gassing‐in method for three different mixing models in batchwise contacting: mixed gas and liquid (MMB); plug‐flow gas and mixed liquid (PMB); and plug‐flow gas and plug‐flow liquid (PPB). TheKLavalues obtained from the new method were consistent with those of the method of Bartholomew et al. Discrimination between the models appeared to be not important for the 1‐m‐high column, but the theoretical analysis revealed that it would become necessary for colu

ISSN:0006-3592    

DOI:10.1002/bit.260340905

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

年代:1989

数据来源: WILEY

摘要:

AbstractAcetone–butanol–ethanol (ABE) production by immobilizedC. acetobutylicumcells is studied in a novel microporous hollow fiber based tubular fermentor–extractor. The solvent 2‐ethyl‐l‐hexanol is used for in situ dispersion‐free extraction of products. A mathematical model for simultaneous fermentation and extraction of the products has been investigated. The predicted as well as experimental data follow the same trend. The experimentally observed value of total solvent productivity increased by more than 40% as a result of in situ solve

ISSN:0006-3592    

DOI:10.1002/bit.260340906

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

年代:1989

数据来源: WILEY

摘要:

AbstractOptimal operating conditions have been determined for recombinantEscherichia colicells in a fed‐batch and two‐stage continuous fermentors. The model expression system used in this article was theE. coli trppromoter cloned on plasmids. Model equations for cell growth and cloned‐gene expression have been formulated and used to evaluate process performances under different operating modes. The operating variables manipulated for maximum performance include the timing of IAA addition to derepress transcription from thetrppromoter. The total operating period and the nutrient concentration profile during fermentations. For a fed‐batch mode, the performance was significantly improved by adjusting the IAA addition (environmental switch) time relative to the total operation period. It was found that the optimal switching time exists for a given total operation period. For a two‐stage continuous fermentation system, the productivity is more sensitive to the combination of the dilution rates than to the volume ratio of two reactors. In general, as long as the down time is less than the total operation time in the fed‐batch mode, the fed‐batch mode gives higher productivity than the two‐stage co

ISSN:0006-3592    

DOI:10.1002/bit.260340907

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe enzymatic conversion of gaseous substrates represents a novel concept in bioprocessing. A critical parameter in such systems is the water activity,AwThe present article reports the effect ofAwon the catalytic performance of alcohol oxidase acting on ethanol vapors. Enzyme activity in the gas‐phase reaction increases several orders of magnitude, whereas the thermostability decreases drastically whenAwis increased from 0.11 to 0.97. The enzyme is active on gaseous substrates even at hydration levels below the monolayer coverage. Enhanced thermostability at lower hydrations results in an increase in the optimum temperature of the gas‐phase reaction catalyzed by alcohol oxidase. The apparent activation energy decreases asAwincreases, approaching the value obtained for the enzyme in aqueous solution. The formation of a pread‐sorbed ethanol phase on the surface of the support is not a prerequisite for the reaction, suggesting that the reaction occurs by direct interaction of the gaseous substrate with the enzyme. The gas‐phase reaction follows Michaelis–Menten kinetics, with aKmvalue almost 100 times lower than that in aqueous solution. Based on vapor–liquid equilibrium data and observedKmvalues, it is postulated that during the gas‐phase reaction the ethanol on the enzyme establishes an equilibrium with the ethanol vapor similar to that between ethanol in water and ethanol in

ISSN:0006-3592    

DOI:10.1002/bit.260340908

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

年代:1989

数据来源: WILEY

摘要:

AbstractReactive polymers have been prepared by copolymeriz‐ingN‐isopropyl acrylamide (NIPAM) withN‐acryloxy‐succinimide (NASI) or glycidyl methacrylate (GMA). The amino groups of ligands could react with the residues of NASI or GMA and the polymers could be precipitated by temperature and/or salinity variation, since they contained the NIPAM residues. As a model,p‐aminobenza‐midine, a trypsin inhibitor, was attached to the polymers to form water‐soluble macroligands, capable of selectively binding trypsin from a trypsin–chymotrypsin solution. After precipitation of the macroligand–trypsin complex, followed by dissociation, approximately 82% trypsin was isolated. The NIPAM‐GMA copolymer was also reacted with immunogammaglobulin (IgG) and alkaline phosphatase (AP). It was demonstrated that the IgG bearing polymer was able to bind protein A and the whole complex was precipitable. The reactive polymer was also used for direct immobilization of AP which was active in

ISSN:0006-3592    

DOI:10.1002/bit.260340909

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

年代:1989

数据来源: WILEY

摘要:

AbstractPhotomixotrophic suspensions ofGlycine max(soybean) andPinus elliottii(slash pine) have been successfully cultured in a hybrid stirred tank photobioreactor using a novel cell‐lift impeller. A cell‐lift impeller exhibited cell viabilities over 90% and an average cell aggregate size of 1.0 mm or less. Flat‐bladed turbines produced equivalent biomass to the cell‐lift impeller, but cell viability was reduced (85%) and cell aggregate size increased (3–5 mm diameter). Maximum fresh weights of 82 g L−1(soybean) and 52 g L−1(slash pine) were achieved in 15 days using continuous lighting (90–100 μE m−2s−1) and supplemental 2% CO2inlet gas. Maximum biomass was achieved using an impeller speed of 60 rpm with air‐flow rate of 0.2 vvm for the cell‐lift impeller and the pair of flat bladed turbines. The lag and early exponential phases were characterized by (1) rapid hydrolysis of sucrose followed by preferential use of glucose and (2) a reduction in chlorophyll levels. Carbon dioxide (2%–5%) was an essential nutrient for photomixotrophic cell

ISSN:0006-3592    

DOI:10.1002/bit.260340910

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe bulk theological properties of exopolymers produced by three species of microalgae are destroyed by shear stress. The properties are drag reduction in capillary pressure flow and low shear rate viscosity. As such, shear stress constitutes an experimental probe into the macromolecular structure which effects bulk Theological properties. Native and sheared exopolymer solutions were subjected to analysis by electrophoresis, size exclusion chromatography, hydrolysis, dialysis, and reducing end‐group analysis. The evidence indicates that shearing did not break the glycoside backbone of these exopolymers, rather shearing disrupted subtle interactions between copolymers. The interactions necessary for bulk rheological properties are likely at the quaternary level of macromolecular organization, specifically weak aggregation

ISSN:0006-3592    

DOI:10.1002/bit.260340911

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

年代:1989

数据来源: WILEY