摘要:

AbstractThe mechanism of extraction of rat cytochrome b5from water into a sodium dioctylsulfosuccinate (AOT) micellar organic phase was studied using protein engineering of surface charged residues. The extraction behavior of native cytochrome b5and modified proteins with substitutions of the type glutamic acid → lysine at positions 44 (E44K), 56 (E56K), and 92 (E92K), was studied as a function of pH. The results indicate that an important mechanism of extraction is an electrostatic interaction of this protein with the negatively charged surfactant. We demonstrate that it is possible to improve extraction by engineering the protein surface charge, increasing the driving force responsible for the protein transfer to the micellar phase. © 1994 John Wiley&Sons, I

ISSN:0006-3592    

DOI:10.1002/bit.260440702

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

年代:1994

数据来源: WILEY

摘要:

AbstractThis article presents a method to test the presence of relatively small systematic measurement errors; e.g., those caused by inaccurate calibration or sensor drift. To do this, primary measurements—flow rates and concentrations—are first translated into observed conversions, which should satisfy several constraints, like the laws of conservation of chemical elements. This study considers three objectives:1.Modification of the commonly used balancing technique to improve error sensitivity to be able to detect small systematic errors. To this end, the balancing technique is applied sequentially in time.2.Extension of the method to enable direct diagnosis of errors in the primary measurements instead of diagnosing errors in the observed conversions. This was achieved by analyzing how individual errors in the primary measurements are expressed in the residual vector.3.Derivation of a new systematic method toquantitativelydetermine the sensitivity of the error, is that error size at which the expected value of the chisquare test function equals its critical value.The method is applied to industrial data demonstrating the effectiveness of the approach. It was shown that, for most possible error sources, a systematic errors of 2% to 5% could be detected. In given application, the variation of the N‐content of biomass was appointed to be the cause of errors. © 1994 John Wiley&Son

ISSN:0006-3592    

DOI:10.1002/bit.260440703

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

年代:1994

数据来源: WILEY

摘要:

AbstractHydrolysis reactions of homopolysaccharides, which differ in their degree of branching, and mixtures of linear and branched polymers were carried out with α‐amylase. The branching structures of both the original amylopectin substrate and the cluster domains of amylopectin, obtained by ethanol precipitation of the products of the action of α‐amylase, were characterized via enzymatic digestion with debranching enzyme (i.e., isoamylase), followed by the fractions of the resulting products using gel filtration chromatography. The structural properties (i.e., molecular weight, molecular weight distribution, and branching characteristics) of the resulting products during depolymerization of amylose, amylopectin and their mixtures via α‐amylase were characterized by size exclusion chromatography coupled with a low angle laser right scattering (SEC/LALLS) technique. It was determined that substrate branching characteristics strongly influence both the observed enzymatic activity as well as the enzyme's action pattern. A simplified kinetic model that represents the hydrolysis reactions of amylose and amylopectin mixtures via endo‐acting α‐amylase is proposed. We found that that reaction kinetics (i.e., enzyme affinity) was also governed by the substrate's conformation in solution. The relationships between the mass fraction of branched polymers and the kinetic parameters during α‐amylolysis were compared with those predicted by the kinetic model. Excellent agreement was found between the model predictions and the experimental observations. The results reported here imply and interrelationship between enzyme action and polymeric substrate structural properties. © 1994 Joh

ISSN:0006-3592    

DOI:10.1002/bit.260440704

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

年代:1994

数据来源: WILEY

摘要:

AbstractA detailed physico‐chemical analysis of two foaming fungal fermentations was carried out to identify that key groups of compounds responsible for foam formation. Fermentations were carried out on a 20‐L scale in a stirred aerated tank, over 7 days, using a commercial, defined medium. The organisms investigated werePenicillium herqueii, a hyphomycete, and an unidentified Ingoldian fungus. Samples of broth and, where possible, foam were analyzed to determine which groups of compounds were concentrated into generated foams. Surface tension, bulk viscosity, and antifoam A concentration were additionally determined in broth samples. To date the cause of foaming in fermentations has been attributed to the surfactant properties of extracellular proteins. This assumption was tested and found to be incomplete as many additional groups of biochemicals were found to be enriched into the foam. The results of the investigation revealed the presence of proteins, carbohydrates, α‐keto acids, and lipophilic biosurfactants, particularly extracellular pigments, enriched within stable foams. © 1994 John Wiley&So

ISSN:0006-3592    

DOI:10.1002/bit.260440705

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

年代:1994

数据来源: WILEY

摘要:

AbstractSubstrate limited fed batch cultures were used to study growth and overflow metabolism in hybridoma cells. A glucose limited fed batch, a glutamine limited fed batch, and a combined glucose and glutamine limited red batch culture were compared with batch cultures. In all cultures μ reaches its maximum early during growth and decreases thereafter so that no exponential growth and decreases thereafter so that no exponential growth rate limiting, although the glutamine concentration (>0.085mM) was lower than reported Ksvales and glucose was below 0.9mM; but some other nutrients (s) was the cause as verified by simulations. Slightly more cells and antibodies were produced in the combined fed batch compared with the batch culture. The specific rates for consumption of glucose and glutamine were dramatically influenced in fed batch cultures resulting in major metabolic changes. Glucose limitation decreased lactate formation, but increased glutamine consumption and ammonium formation. Glutamine limitation decreased ammonium and alanine formation of lactate, alanine, and ammonium was negligible in the dual‐substrate limited fed batch culture. The efficiency of the energy metabolism increased, as judged by the increase in the cellular yield coefficient for glucose by 100% and for glutamine by 150% and by the change in the metabolic ratios lac/glc, ala/ln, and NHx/ln, in the combined fed culture. The data indicate that a larger proportion of consumed glutamine enters the TCA cycle through the glutamate dehydrogenase pathway, which releases more energy from glutamine than the transamination pathway. We suggest that the main reasons for these changes are decreased uptake rates of glucose and glutamine, which in turn lead to a reduction of the pyruvate pool and a restriction of the flux through glutaminase and lactate dehydrogenase. There appears to be potential for further cell growth in the dual‐substrate‐limited fed batch culture as judged by a comparison of μ in the different cultures. © 1994 John Wiley&S

ISSN:0006-3592    

DOI:10.1002/bit.260440706

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

年代:1994

数据来源: WILEY

摘要:

AbstractThis article describes a fully automated system for the on‐line monitoring and closed‐loop control of a fed‐batch fermentation of recombinantEscherichia coli, and presents two case studies of its used in limiting production of unwanted byproducts such as acetic in fed‐batch fermentations. The system had two components. The first components, on‐line monitoring, comprised an aseptic sampling device, a microcentrifuge, and HPLC System. These instruments removed a Sample from a fermentor, spun it at high speed to separate solid and liquid components, and then automatically injected the supernatant onto an HPLC column for analysis. The second component consisted of control algorithms programmed using the LabView visual programming environment in a control computer that was linked via a remote components were linked so that results from the on‐line HPLC were captured and used by the control algorithm was designed to demonstrate coarse feedback control to confirm the operability of the controller. The second case study showed how the system could be used in a more sophisticated feedings strategy providing fine control and limiting acetate concentration to a low level throughout the fermentation. © 1994 John Wil

ISSN:0006-3592    

DOI:10.1002/bit.260440707

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

年代:1994

数据来源: WILEY

摘要:

AbstractA new method is presented to precipitate proteins and amino acids from reverse micelles by dehydrating the micelles with molecular sieves. Nearly complete precipitation is demonstrated for α‐chymotrypsin, cytochromec, and trytophan from 2‐ethylhexyl sodium sulfosuccinate (AOT)/isooctane/water reverse micelle solutions. The products precipitate as a solid powder, which is relatively free of surfactant. The method does not require any manipulation of pH, ionic strength, temperature, pressure, or solvent composition, and is applicable over a broad range of these properties. This general approach is compared with other techniques. This general approach is compared with other techniques for the recovery of biomolecules from reverse micelles. © 1994 John Wiley&Sons

ISSN:0006-3592    

DOI:10.1002/bit.260440708

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

年代:1994

数据来源: WILEY

摘要:

AbstractIn the aerobic phase of the biological phosphorus removal process, poly‐β‐hydroxybutyrate, produced during anaerobic conditions, is used for cell growth, phosphate uptake, and glycogen formation. A metabolic model of this process has been developed. The yields for growth, polyphosphate and glycogen formation are quantified using the coupling of all these conversions to the oxygen consumption. The uptake of phosphate and storage as polyphosphate is shown to have a direct effect on the observed oxygen consumption in the aerobic phase. The overall energy requirements for the P‐metabolism are substantial: 25% of the acetate consumed during anaerobic conditions and 60% of the oxygen consumptions is used for the synthesis of polyphosphate and glycogen. © 1994 John Wiley&So

ISSN:0006-3592    

DOI:10.1002/bit.260440709

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

年代:1994

数据来源: WILEY

摘要:

AbstractLangmuir‐Blodgett (LB) films of monoamine oxidase (MAO) have been formed on the surface f a polypropylene membrane using amphiphilic polyelectrolytes. The enzyme activity of such protein‐polyelectrolyte films was measured by a Clark electrodes. It was shown that in LB films thus formed the use of amphiphilc polyelectrolytes, MAO activity was higher than in polyelectrolyte‐free LB films. Immobilization of MAO with branched polyethylenimine modified on 12% by laurylchain led to pronounced changes in its catalytic properties. The dependence of the enzyme's kinetic parameters on amphiphilic polyelectrolyte structures was discussed. © 1994 John Wiley&Son

ISSN:0006-3592    

DOI:10.1002/bit.260440710

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe capability of hydrogen photoproduction under high cell density conditions was examined using synchronously grown cells of nitrogen‐fixingSynechococcussp. Miami BG 043511. Optimum hydrogen yield was obtained when vessels (25 ml) contained 0.2 to 0.3 mg chlorophyllain 3‐mL cell suspension. During a 24‐h incubation period, an initial phase of hydrogen and carbon dioxide production and a subsequent phase of carbon dioxide uptake and oxygen accumulated as major products after 24 h. after the initial 24‐h. After the initial 24‐h incubation, as high as 7.4 and 3.7 L (at standard condition) of hydrogen and oxygen, respectively, accumulated in vessels with 22‐ml gas phase. This indicated that the pressure in the flask increased to 1.5 atmosphere. Energy conversion efficiency based on photosynthetically active radiation (25 W/m2) was about 2.6%. However, increased pressure somehow reduced the duration of hydrogen production. Duration of hydrogen and oxygen production was prolonged by periodical (24‐h interval) gas replacement during incubation. © 1994 John W

ISSN:0006-3592    

DOI:10.1002/bit.260440711

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

年代:1994

数据来源: WILEY