ISSN:0006-3592    

DOI:10.1002/bit.260120502

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

年代:1970

数据来源: WILEY

摘要:

AbstractThe utilization of an exogenous substrate by enzyme inside a bacterial cell can be limited by diffusion up to the cell, penetration of the cell, diffusion within the cell, and/or attack by internal enzyme. For small molecular weight substrates such as galactosides, and for bacteria such asEscherichia colithe diffusion steps are not rate limiting even with the permeases fully induced and the external concentration of substrate low. In permeaseless organisms with more than about 20 enzyme molecules per cell, permeation ofO‐nitrophenyl‐β‐D‐galactoside through the membrane is limiting. Thus, a single initiation of transcription of a lactose message suffices to yield enough enzyme molecules to switch an uninduced cell from enzyme limitation to permeability limitation. Subsequent initiations change the cellular activity very little. This transition can be followed by assaying enzyme activity of both intact and lysed cell suspensions. In this way the induction response amongst cells in growing populations at high inducer concentrations has been found to be uniform. It was found that nearly all of the cells from balanced growing culture are immediately inducible even with doubling times as short as 7.6 hrs. At 24 hrs about 1/3 of the cells are inert at any time, but all cells synthesize enzyme within a 3‐hour period. At low inducer concentration or in the present of catabolite repressor the rate of initiation is greatly decreased; this leads to a non uniform distribution of enzyme within the cells, which is readily detected by the experimental technique. In addition to developing the kinetics for enzyme contained in cells, the distribution of the enzyme among uninduced bacteria is

ISSN:0006-3592    

DOI:10.1002/bit.260120503

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

年代:1970

数据来源: WILEY

摘要:

AbstractHigh substrate concentrations inhibit growth and may distort the metabolism of microorganisms. Mechanisms causing substrate inhibition are discussed and used to derive several mathematical models representative of the entire concentration range, including stimulation of growth by low substrate concentrations. These kinetic models are tested with a variety of batch culture measurements of specific growth rate and respiration rate at widely‐ranging substrate concentrations. Using one of the kinetic models, equations are developed for batch, continuous, and exponential‐feed reactors. Comparison of results obtained in continuous culture with results from exponential‐feed culture systems is shown to offer a novel experimental method for evaluating the effect of the cell age distribution on the properties and metabolic activity of a cu

ISSN:0006-3592    

DOI:10.1002/bit.260120504

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

年代:1970

数据来源: WILEY

摘要:

AbstractIn this work, a mathematical model which can be used to describe butch growth in fermentations with two liquid phases present is developed for systems in which the growth limiting substrate is dissolved in the dispersed phase. The model takes into account the drop size distribution, the rate of adsorption of cells on the drop surface, the rate of desorption of cells from the drop surface, substrate transport between phases, phase equilibrium, and growth kinetics. The model also considers the effect, of coalescence and redispersion of oil drops in the system. It is assumed that the composition of the dispersed phase is such that substrate utilization from it causes little or no change in the interfacial area. A discrete uniform distribution and a discrete normal distribution which is obtained from an experimental distribution curve are used as drop size distributions. Simulation results are obtained for a wide range of parameter values using the IBM S/360 Continuous System Modeling Program.

ISSN:0006-3592    

DOI:10.1002/bit.260120505

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

年代:1970

数据来源: WILEY

摘要:

AbstractA number of experimental studies on the dynamic, behavior of the chemostat have shown that the specific growth rate does not, instantaneously adjust to changes in the concentration of limiting substrate in the chemostat following disturbances in the steady state input limiting substrate concentration or in the steady state dilution rate. Instead of an instantaneous response, as would be predicted by the Monod equation, experimental studies have shown that the specific growth rate experiences a dynamic lag in responding to the changes in the concentration of limiting substrate in the culture vessel. The observed dynamic lag has been recognized by researchers in such terms asan inertial phenomenonand asa hysteresis effect, but as yet a systems engineering approach has not been applied to the observed data. The present paper criticizes the use of the Monod equation as a dynamic relationship and offers as an alternative a dynamic equation relating specific growth rate to the limiting substrate concentration in the chemostat. Following the development of equations, experimental methods of evaluating parameters are discussed. Dynamic responses of analog simulations (incorporating the newly derived equations) are compared with the dynamic responses predicted by the Monod equation and with the dynamic responses of experimental chemostats.

ISSN:0006-3592    

DOI:10.1002/bit.260120506

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

年代:1970

数据来源: WILEY

ISSN:0006-3592    

DOI:10.1002/bit.260120507

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

年代:1970

数据来源: WILEY

摘要:

AbstractTwo kinds of mathematical models have been developed for batch penicillin fermentations: (1) general models, based on averaged, nondimensionalized cell and penicillin synthesis curves from plant, scale fermentors and (2) particular models developed from specific sets of experimental data from two sources. Parameter‐temperature functions used with the general models were assumed to have general shapes which could apply to many fermentations, i.e., they were based on the familiar temperature response of enzyme‐catalyzed reactions. Parameter‐temperature functions for the particular models were determined from experimental data for batch runs at various tempera

ISSN:0006-3592    

DOI:10.1002/bit.260120508

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

年代:1970

数据来源: WILEY

摘要:

AbstractAn enzyme kinetic model has been proposed to describe fermentation processes. This type of model was chosen because it is biologically sound, can incorporate all of the important engineering control variables, and can draw upon, in its development, the extensive kinetic literature. An intial qualitative test for this model was made on the gluconic acid fermentation. A necessary check of the model was that Monod's empirical cell growth and yield equations were derived as a special case. The model also offered an explanation for the hysteresis behavior of the gluconic acid production rate as a function of gluconolactone.

ISSN:0006-3592    

DOI:10.1002/bit.260120509

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

年代:1970

数据来源: WILEY

ISSN:0006-3592    

DOI:10.1002/bit.260120510

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

年代:1970

数据来源: WILEY

ISSN:0006-3592    

DOI:10.1002/bit.260120501

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

年代:1970

数据来源: WILEY