摘要:

AbstractAn adaptive steady‐state optimization algorithm is presented and applied to the problem of optimizing the production of biomass in continuous fermentation processes. The algorithm requires no modeling information but is based on an on‐line identified linear model, locates the optimum dilution rate, and maintains the chemostat at its optimum operating condition at all times. The behavior of the algorithm is tested against a dynamic model of a chemostat that incorporates metabolic time delay, and it is shown that large disturbances in the subtrate feed concentration and the specific growth rate, causing a shift in the optimum, are handled well. The developed algorithm is also used to drive a methylotroph single‐cell production process to its op

ISSN:0006-3592    

DOI:10.1002/bit.260300302

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

年代:1987

数据来源: WILEY

摘要:

AbstractIn gas–liquid dispersions based on viscous non‐Newtonian fluids, numerous very small bubbles are formed due to their high residence times in contacting devices such as bubble columns. The influence of these small bubbles on the measurement of the volumetric mass transfer coefficient in the contactor by the dynamic CO2gas analysis method is discussed. It is found that their effect on this measuring technique is insignificant compared to that when using the conventional dissolved‐oxygen tech

ISSN:0006-3592    

DOI:10.1002/bit.260300303

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

年代:1987

数据来源: WILEY

摘要:

AbstractDistribution coefficients and selectivities of a number of mixed solvent systems have been determined in order to assess their suitability in preferentially extracting ethanol from aqueous solution. The measured values of distribution coefficients and selectivities differ substantially from the values estimated by interpolating between the pure solvents.

ISSN:0006-3592    

DOI:10.1002/bit.260300304

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe changes in growth kinetics in aerobic batch cultures ofKlebsiella pneumoniaewere followed by measurements of extracellular metabolites, rates of gas exchange, dissolved oxygen tension, pH, and carbon balance at all stages of growth. When the initial growth‐limiting glucose concentration in media without pH control was increased from 1.0 g carbon L−1to 2.2 g carbon L−1, the number of different, mainly acidic, extracellular metabolites of glucose at the end of exponential growth increased, while the proportion of acetate decreased. During the postexponential growth phase, the extracellular metabolites were oxidized, resulting in an increasing complexity of changes in pH, gas exchange, and dissolved oxygen tension with increasing initial substrate concentration. All these parameters showed concomitant stepwise changes. This pattern was independent of the dissolved oxygen tension in the range 30–200 μM. When pH was kept constant, the number, slope, and relative magnitude of the steps in gas exchange and dissolved oxygen tension were pH‐dependent, being most complex at low pH. Detailed carbon balances showed that 20% of the initial glucose was converted into extracellular metabolites at the end of exponential growth at neutral pH. In the postexponential phase, pyruvate (2%) was reoxidized first followed by acetate (13%). The observed molar growth yield coefficient (YATP) was 8.4 if the transitory occurrence of pyruvate and acetate was accounted for, and 6.4 if it was neglected. The corrected observed molar growth yield coefficient (Y′ATP) was 9.4 and compared well with the true molar growth yield coefficient (Y MaxATP), which was found to be 11.0. Specificin siturespiration rates of the exponential growth phase of cultures grown at different controlled pH values compared well within situvalues for energy‐limited chemostat grown cells at the same growth rates, suggesting that growth in the batch culture was energy‐limited throughout the exponential growth phase. This view was supported by low levels of intracellular glycogen and exopolysaccharides of all cultures, by the value ofY′ATPof 9.4, and by a constant specific production rate of the extracellular metabolites throughout exponential growth. It was concluded that even under strictly aerobic conditions, control of pH is as important as control of dissolved oxygen tension during growth of enterobacteriace

ISSN:0006-3592    

DOI:10.1002/bit.260300305

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

年代:1987

数据来源: WILEY

摘要:

AbstractAmylase synthesis by the yeastsSaccharomycopsis fibuligeraandSchwanniomyces castelliiandalluviusis repressed by glucose. Steady state continuous culture data for amylase activity,E, biomass concentration,X, and reducing sugar concentration,S, were fitted to the three‐parameter catabolite repression model\documentclass{article}\pagestyle{empty}\begin{document}$ \frac{E}{X} = \frac{{[1 + a(S/X)]}}{{[1 + b(S/X)]}}, $\end{document}and biomass productivity,DX, and amylase productivity,DE, were determined forS. castelliiandS. alluviu

ISSN:0006-3592    

DOI:10.1002/bit.260300306

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

年代:1987

数据来源: WILEY

摘要:

AbstractBothkLaandkLmeasurements were carried out by an unsteady state technique at impeller speeds ranging from 1.6 to 5.8 s−1in a mechanically agitated animal cell culture vessel of working volume 1.5 L. Checks were made that the time constant of the oxygen electrode was negligible compared to the time for aeration and that the oxygen electrode reading was not a function of agitator speed in the range employed. ThekLvalues by surface aeration of (1.18–3.54) × 10−5m/s andkLavalues by sparged aeration of (2.8–8.5) × 10−4s−1were found. The former are in reasonable agreement with published experimental values and the latter in accord with values estimated from published correlations based on agitator power input and aeration rate. The fluids used were water, basal medium, and basal medium supplemented with 5% (v/v) foetal calf serum; for each of these,kLandkLavalues were similar. However, the addition of silicone antifoam (6 PPM) reduced thekLaval

ISSN:0006-3592    

DOI:10.1002/bit.260300307

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe kinetics of the hydrolysis of soluble starch by simultaneous use of β‐amylase and either isoamylase or pullulanse was studied experimentally for a wide range of subtrate and enzyme concentrations. A kinetic expression was constituted for maltose production by β‐armylase, which was stimulated by an increase in linear linkage portions due to the debranching enzyme on amylopectin molecules. As a result, calculations by the kinetic expression agreed with time course data under various condi

ISSN:0006-3592    

DOI:10.1002/bit.260300308

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe effect of water on equilibria for hydrolytic reaction in reversed micelles has been investigated using lipase as a model enzyme. The effect of water on equilibria has been ignored for hydrolase reactions in an aqueous phase. In a reversed micellar system, however, the equilibrium of the lipase reaction was changed when water was added during the hydrolytic reaction. Furthermore, equilibrium fractional conversion is affected by the initial water concentration, being shifted to higher values with higher water concentrations, with other reaction conditions being held constant, indicating that the reaction should be regarded as a two‐substrate process. Equations corresponding to a two‐substrate, second‐order reversible model are derived and used for further analysis. The progress curves predicted from the rate equations agree very well with the experimental results under various reaction conditions. The values of the molar ratio of water to surfactant (R) which maximize the initial reaction rate and maximum fractional conversion is predictable from the derived rate equations and the resulting relationship betweenRand the kinetic cons

ISSN:0006-3592    

DOI:10.1002/bit.260300309

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe design of bioreactors for genetically modified bacterial cultures would benefit from predictive models. Of particular importance is the interaction of the external environment, cell physiology, and control of plasmid copy number. We have recently developed a model based on the molecular mechanisms for control of replication of Co1E1 type plasmids. The inclusion of the plasmid model into a single‐cellE. colimodel allows the explicit prediction of the interaction of cell physiology and plasmid‐encoded functions. The model predictions of the copy number of plasmids with the Co1E1 origin of replication carrying a variety of regulatory mutations is very close to that observed experimentally.All of the model parameters for plasmid replication control can be obtained independently and no adjustable parameters are needed for the plasmid model. In this article we discuss the model's use in predicting the effect of operating conditions on production of a protein from a plasmid encoded gene and the stability of the recombinant cells in a continuous cult

ISSN:0006-3592    

DOI:10.1002/bit.260300310

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

年代:1987

数据来源: WILEY

摘要:

AbstractExperimental and modeling studies were conducted to analyze the dynamic response behavior of a phenol‐oxidizing fixed film using a differential, fluidized‐bed bioreactor in a recycle loop with a well‐mixed reservoir. With the bioreactor at steady state, a pulse of phenol was added to perturb the system, and the phenol concentration was monitored continuously until steady state was again achieved.The experimental dynamics were compared with a dynamic mathematical model based on diffusion and reaction within the biofilm, liquid mixing, and biofilm growth. Constant‐pH experiments could be adequately described using an unstructured, double‐Monod kinetic expression with substrate inhibition by phenol.However, in dynamic experiments without pH control, the pH of the liquid phase dropped, and damped oscillations were observed in the phenol concentration and reaction rate trajectories. Oscillatory solutions could not be induced in the model, even when product inhibition was included, and a linear stability analysis did not reveal tendencies toward instability. The cause of the experimental oscillations remain

ISSN:0006-3592    

DOI:10.1002/bit.260300311

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

年代:1987

数据来源: WILEY