摘要:

AbstractThe effects of NH4Cl addition on batch hybridoma cell growth at different external pH values (pHe) were investigated in a bioreactor at constant pH and dissolved oxygen concentration. In agreement with measurements in flasks, changes in pHeover the range 6.8–7.6 had minor effects on growth. Addition of 3 mMNH4Cl had little effect on cell growth while 10 mMNH4Cl caused a substantial growth inhibition, Measurements of the effects of pHeand NH4Cl concentration on cell metabolism gave similar results for cells grown in flasks in an incubator and in the bioreactor. As pHedecreases, the integral cell yield on glucose increases. There is a correlation between the effects of pHeon glycolysis and previous measurements of its effects on intracellular pH (pHi). Increases in NH4Cl concentration were previously determined to decrease pHiand are shown here to decrease the integral cell yield on glucose. At all pHevalues in the absence of NH4Cl, glutamine is depleted at the time the maximum cell density is reached. Both pHedecreases and NH4Cl concentration increases lead to decreases in the integral cell yield on glutamine. Changes in pHeand in the NH4Cl concentration that cause growth inhibition have no effect on the specific antibody production rate for cells grown in flasks in an incubator or in the bioreactor. Changes in the NH4Cl concentration have no effect on the quality of the antibody produced, to a first level of characterizatio

ISSN:0006-3592    

DOI:10.1002/bit.260351102

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

年代:1990

数据来源: WILEY

摘要:

AbstractAn oxygen microsensor was used to measure internal oxygen profiles in biocatalyst particles of different diameter and activity. The particles were made of agarose gel and contained an oxygen reducing enzyme,L‐lactate mono‐oxygenase. The kinetics of the enzyme could be well described by the Michaelis–Menten equation. From the internal substrate concentration profile the intrinsic kinetic parameters were determined by means of fitting a simulated profile to the measurements, using Marquardt's algorithm. The intrinsic kinetic parameters found following this procedure appeared to be independent of particle radius or enzyme loading used, proving the method to be reliable. These parameters were also compared with the kinetic parameters of the free enzyme which were determined in a biological oxygen monitoring system. The intrinsic kinetic parameters showed a decrease with a factor 2.3 forVmvalue and with a factor 2.7 for theKmvalue compared to the parameters for the free enzyme. From this the conclusion can be drawn that the immobilization as such or the carrier material not only can have an effect on the maximum intrinsic conversion rate (Vm) but also on the affinity of the enzyme (Km) for o

ISSN:0006-3592    

DOI:10.1002/bit.260351103

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

年代:1990

数据来源: WILEY

摘要:

AbstractTo examine the effects of volatile components on plant cell growth, a bioreactor control system was developed to simultaneously control the dissolved concentrations of both oxygen and carbon dioxide. The first step in this work was to develop a mathematical model to account for gas–liquid mass transfer; biological utilization and production of O2and CO2; and the series of chemical reactions of CO2in water. Using this model and dynamic measurements for dissolved O2and CO2, it was observed that (1) both absorption and desorption of a volatile component could be described by a single mass transfer coefficient,Kla, and (2)Klavalues for oxygen and carbon dioxide transfer were directly proportional. The second step of this work was to employ the mathematical model in an adaptive feed‐forward strategy to control the dissolved O2and CO2concentrations by manipulating the inlet gas composition to the bioreactor. This strategy allowed dissolved concentrations to be controlled without the need for changing either the total gas flow rate or agitator speed. Adaptive control was required because the volumetric rates of O2and CO2consumption and production vary with time during long term operation and therefore these rates must be continually updated. As the final step, we demonstrated that this control strategy was capable of controlling the dissolved gas concentrations in both short‐ and long‐term studies involving the cultivation ofCatharanthus roseusplan

ISSN:0006-3592    

DOI:10.1002/bit.260351104

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

年代:1990

数据来源: WILEY

摘要:

AbstractSubcellular compartments, such as the vacuole in yeast, play important roles in cell metabolism and in cell response to external conditions. Concentrations of inorganic phosphate and pH values of the vacuole and cytoplasm were determined for anaerobicSaccharomyces cerevisiaecells based upon31P NMR spectroscopy. A new approach allows the determination of these values for the vacuole in cases when the resonance for inorganic phosphate in the cytoplasm overlaps with the resonance for inorganic phosphate in the vacuole. The intracellular inorganic phosphate resonance was first decomposed into two components by computer analysis. The assignments of the components were determined from in vivo correlations of Pichemical shift and the chemical shifts of the cytoplasmic sugar phosphates, and the pH dependency of the resonance of pyrophosphate and the terminal phosphate of poly‐phosphate (PP1) which reside in the vacuole. An in vivo correlation relating PP1and P ivacchemical shifts was established from numerous evaluations of intracellular compositions for several strains ofS. cerevisiae. This correlation will aid future analysis of31P NMR spectra of yeast and will extend NMR studies of compartmentation to cellular suspensions in phosphate‐containing medium. Application of this method shows that both vacuolar and extracellular Piwere phosphate reserves during glycolysis in anaerobicS. cerevisiae. Net transport of inorganic phosphate across the vacuolar membrane was not correlated with the pH gradient across the mem

ISSN:0006-3592    

DOI:10.1002/bit.260351105

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

年代:1990

数据来源: WILEY

摘要:

AbstractMass transfers of O2, CO2, and water vapor are among the key processes in the aerobic, autotrophic cultivation of moderate and extreme thermophiles. The dynamics and kinetics of these processes are, in addition to the obvious microbial kinetics, of crucial importance for the industrial desulfurization of high‐pyritic coal by such thermophiles. To evaluate the role of the temperature on the gas mass transfer,kLameasurements have been used to supplement the existing published data. Oxygen mass transfer from gas (air) to liquid (5 mMH2SO4in water) phase as a function of the temperature has been studied in a laboratory‐scale fermentor. At 15, 30, 45, and 70°C, (kLa)ovalues (for oxygen) were determined under three different energy input conditions by the dynamic gassing in/out method. The (kLa)owas shown to increase under these conditions with increasing temperature, and straight lines were obtained when the logarithm of (kLa)owas plotted against the temperature. By multiplying the equilibrium concentration of O2in water with (kLa)omaximal, O2transfer capacities were calculated. It appeared that in finite of a decreased solubility of O2at elevated temperature in mechanically mixed fermentors the calculated transfer capacities showed only minor changes for the range between 15 and 70°C. However, in an air‐mixed fermentor the transfer capacity of O2decreased slowly but steadily.Carbon dioxide mass transfer was predicted by calculations on the basis of the data for oxygen transfer. The maximal CO2transfer capacity, calculated as the product of the equilibrium CO2concentration times (kLa)c, decreased slowly as the temperature increased over the range 15–70°C under all three energy input conditions. Subsequent process design calculations showed that for aerobic, autotrophic cultures, CO2limitation is more likely to occur than O2

ISSN:0006-3592    

DOI:10.1002/bit.260351106

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

年代:1990

数据来源: WILEY

摘要:

AbstractA gene for ethionine resistance isolated from the yeastSaccharomyces cerevisiaeDKD‐5D‐H conferred on the yeast cells resistance to seleno‐L‐methionine and capability to produceS‐adenosyl‐L‐methionine in the cells. An enzymatic study of theL‐methionine synthetic pathway ofL‐methionine proto‐ and auxotrophs and in dried yeast cells with or without the gene suggested that the cloned gene for ethionine resistance is responsible for the activity ofS‐adenosyl‐L‐methionine synthase. To produceS‐adenosyl‐L‐methionine by yeast cells transformed with the ethionine resistance gene, some cultu

ISSN:0006-3592    

DOI:10.1002/bit.260351107

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe extracellular enzymes and cell mass from the pregrownPhanerochaete chrysosporiumcultures were used for the degradation of PCP. The use of both extracellular enzymes and cell mass resulted in extensive mineralization of PCP, while the action of only the crude extracellular enzymes led to the formation of a degradation intermediate (TCHD). A kinetic model, which describes the relationship among PCP degradation, initial PCP concentration, dosage of extracellular enzymes, and cell mass concentration, was developed. Based on this model, various effects of initial PCP concentration, dosage of extracellular enzymes, and cell mass concentration were evaluated experimentally. It was found that when initial PCP concentration is lower than 12 μmol/L, the model of a parallel‐series first‐order reaction is sufficient to describe the degradation process. PCP disappearance and mineralization were enhanced by increasing either the extracellular enzyme concentration or the cell mass concentration. As high as 70% of PCP mineralization could be obtained by using a higher dosage of extracellular enzymes and cell mass. Various parameters of the kinetic model were determined and the model was verified experimentally. Simulation using this model provided the criteria needed to choose rational dosages of extracellular enzymes and cell mass for the degradation of PCP. Data reported allow some insight into the function of the extracellular enzymes and cell mass ofP. chrysosporiumin degradation processes of toxic pollutants and assist in the design and evaluation of practical bioremediation met

ISSN:0006-3592    

DOI:10.1002/bit.260351108

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe effect of fluid flow and laminar shear on bacterial uptake was examined under conditions representative of the fluid environment of unattached and attached cells in wastewater treatment bioreactors. Laminar shear rates below 50 s−1did not increase leucine uptake by suspended cultures ofZoogloea ramigera. However, leucine uptake by cells fixed in a flow field of ∼ 1 mm s−1was 55–65% greater than uptake by suspended cells. Enhanced microbial uptake with advective motion is consistent with mass transfer rates calculated using Sherwood number correlations. Advective flow increases microbial uptake by increasing collisions between substrate molecules and cells through compression of the concentration boundary layer surrounding a cell. The rate of leucine uptake suggests that binding proteins used to transport leucine into the cell can occupy approximately 1% of the cell surfa

ISSN:0006-3592    

DOI:10.1002/bit.260351109

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe results of experiments in a fixed‐bed reactor and a CSTR containing urease immobilized on a nonporous support and conducted in the absence of diffusional limitations are reported. Kinetic parameters were established by separate batch experiments. The key observation was that the product ammonia attacked thefreeform of the enzyme and thereby illustrates the importance of mechanism in determining deactivation kinetic

ISSN:0006-3592    

DOI:10.1002/bit.260351110

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

年代:1990

数据来源: WILEY

摘要:

AbstractIt has been previously demonstrated that the chemoautotroph and facultative anaerobe,Thiobacillus denitrificans, may be cultured aerobically or anaerobically in batch and continuous reactors on H2S(g) under sulfide‐limiting conditions. A process has been proposed for the removal of H2S from gases based on oxidation of H2S byT. denitrificans. Described here is a study of H2S oxidation by otherThiobacilli, the purpose of which has been to determine whether otherThiobacillioffer any advantages overT. denitrificansin the aerobic oxidation of H2S. Although four other species ofThiobacilluswere found to grow on H2S as an energy source, none offer a clear advantage overT. denitrifican

ISSN:0006-3592    

DOI:10.1002/bit.260351111

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

年代:1990

数据来源: WILEY