摘要:

AbstractSustained oscillations have been observed in continuous cultures ofSaccharomyces cerevisiae. These oscillations appear spontaneously under aerobic conditions and may constitute a severe limitation for process control. We have found that oscillations arise only in a well defined range of dilution rates and dissolved oxygen values. The period of the oscillations is related, but not equal, to the mass doubling time, and shows a relation ship with both the parent cells and daughter cells generation times. At high dilution rates two oscillatory regimens, with different periods, are observed. The analysis of the budding index shows a marked degree of synchronization of the culture, however significant differences, both in phase and in amplitude, are ob served if the budding index of parent cells and of daughter cells are considered separately. The complex changes of the cell population are clearly demonstrated by the continuous and periodic modification of both cell volume distributions and protein distributions. Ethanol is always accumulated before the drop of dissolved oxygen concentration and one of the peaks of budding index. We propose a model that explains the insurgence of these oscillation as a consequence of changes in cell cycle parameters due to alternate growth in glucose and in ethanol.

ISSN:0006-3592    

DOI:10.1002/bit.260320402

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

年代:1988

数据来源: WILEY

摘要:

AbstractAn asynchronous bacterial population has been approximated using a finite number of “computer” cells, each based on a complex single‐cell model forEscherichia coli.This formulation correctly simulates the transient responses of protein and total cell mass synthesis rate to the sudden increase in the concentration of limiting energy source in the growth medium. Experimentally observed responses of rRNA and mRNA synthesis rates to growth rate shifts are qualitatively mirrored by the model. Simulation trends following those of arel−mutant suggest that model modifications are needed to describe the dynamics of the stringent response. Simulations of the responses of recombinant populations to plasmid amplification or plasmid promoter induction also result in behavior similar to that determined experimentally. The calculated responses for recombinant populations subjected to constant promoter induction or cyclic induction‐noninduction lead to the conclusion that inducible systems give greater productivity than those with fixed promoter strength. This formulation may be utilized as a basis for exploring other aspects of recombinant population

ISSN:0006-3592    

DOI:10.1002/bit.260320403

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

年代:1988

数据来源: WILEY

摘要:

AbstractA generalized form of Monod kinetics is proposed to account for all kinds of product, cell, and substrate inhibition. This model assumes that there exists a critical inhibitor concentration above which cells cannot grow, and that the constants of the Monod equation are functions of this limiting inhibitor concentration. Methods for evaluating the constants of this rate form are presented. Finally the proposed kinetic form is compared with the available data in the literature, which unfortunately is very sparse. In all cases, this equation form fitted the data very well.

ISSN:0006-3592    

DOI:10.1002/bit.260320404

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe effect of hydrogen and carbon dioxide partial pressure on the growth of the extremely thermophilic archaebacteriumPyrodictium brockiiat 98°C was investigated. Previous work with this bacterium has been done using an 80:20 hydrogen‐carbon dioxide gas phase with a total pressure of 4 atm; no attempt has been made to determine if this mixture is optimal. It was found in this study that reduced hydrogen partial pressures affected cell yield, growth rate, and sulfide production. The effect of hydrogen partial pressure on cell yield and growth rate was less dramatic when compared to the effect on sulfide production, which was not found to be growth‐associated. Carbon dioxide was also found to affect growth but only at very low partial pressures. The relationship between growth rate and substrate concentration could be correlated with a Monod‐type expression for either carbon dioxide or hydrogen as the limiting substrate. The results from this study indicate that a balance must be struck between cell yields and sulfide production in choosing an optimal hydrogen partial pressure for the growth ofP. b

ISSN:0006-3592    

DOI:10.1002/bit.260320405

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

年代:1988

数据来源: WILEY

摘要:

AbstractGrowth of the parent and acid‐tolerant mutant strains ofClostridiurn thermoaceticumwas examined on a variety of substrates and mixtures of substrates. Nondiauxic growth was noted for both strains on combinations of carbohydrates, organic acids, or a carbohydrate and an organic acid. The mutant strain was able to grow onDL‐lactate as sole energy source. The parent strain would not grow on lactate as sole energy source but consumed lactate when presented with a second fermentable substrate. Neither strain would grow on formate as sole energy source, but both consumed formate when presented with a second fermentable substr

ISSN:0006-3592    

DOI:10.1002/bit.260320406

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

年代:1988

数据来源: WILEY

摘要:

AbstractAn affinity ultrafiltration process has been developed by exploiting affinity binding in conjunction with cross‐flow filtration. The process was proven to possess high resolution, high recovery yield, and ease of scale‐up. The process could purify trypsin from a trypsin‐chymotrypsin mixture batchwise or continuously. Essential for applying this concept was the synthesis of a water‐soluble high‐molecular‐weight polymer bearingm‐aminobenzamidine, a strong and specific trypsin in hibitor. A mathematical model was also developed to describe the dynamic behavior of the newly developed purification process. The model was able to predict the profiles of enzyme concentrations in the process with

ISSN:0006-3592    

DOI:10.1002/bit.260320407

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

年代:1988

数据来源: WILEY

摘要:

AbstractExperimental data from the enzymatic hydrolysis of phenol‐pretreated Swedish wheat straw have been used to evaluate the cost fractions of capital and utility, enzyme, and raw material. Two different raw material prices and varying enzyme prices have been used. The evaluation is based on an empirical model for the enzymatic hydrolysis and a computer program where utility and equipment, enzyme, and raw material prices can be varied. The optimal residence time for the enzymatic hydrolysis is in the range of 70–110 h. A fed‐batch procedure with substrate concentrations higher than 10% oven‐dried material (ODM) and enzyme concentrations in the range (6–10) · 106FPU/ton ODM shou

ISSN:0006-3592    

DOI:10.1002/bit.260320408

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

年代:1988

数据来源: WILEY

摘要:

AbstractAntisera against charged (p‐azobenzoate andp‐azoben zenesulfonate) and uncharged (dinitrophenyl) haptenic groups were produced in rabbits, and the equilibrium characteristics of hapten‐antibody were measured by use of immunoadsorbents. The antibody to the uncharged hapten formed a stable binding with the hapten to the changes in ionic strength and pH. On the other hand, the antibodies to the charged haptens showed affinities sensitive to the changes in pH and ionic strength. Therefore, the effect of the pKaof ionizable haptens on the pH dependence of the hapten‐antibody binding was studied by comparing the interactions between a series of para‐substituted benzoic acids and the anti‐p‐azobenzoate antibody. The pH dependence of the interactions was strongly affected by the pKaof ionizable groups in haptens. Furthermore, the equilibrium characteristics of anti‐p‐aminobenzoyl dipeptides were compared. The characteristics of interactions were affected by the features of am

ISSN:0006-3592    

DOI:10.1002/bit.260320409

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

年代:1988

数据来源: WILEY

摘要:

AbstractA comparison of different immobilized enzyme reactors has been made for the limited modification of soya storage proteins and the products compared with those from action of the soluble enzyme. Clarified total water extracts of soya protein were subjected to the action of subtilisin in a soluble and immobilized form. The sodium dodecyl sulfate (SDS) electrophoresis patterns of soya proteins modified by enzyme in the two forms differed for unbuffered soya protein at the same pH of 8.0. However, identical patterns could be obtained by a downward adjustment of the pH of soya protein treated with immobilized enzyme. The same SDS electrophoresis pattern could be obtained for a packed column of immobilized enzyme and a well‐mixed vessel by buffering. Operation of the column reactor at higher superficial linear velocities (above 1.47 cm/min), higher protein concentrations (8.8% w/v), and prolonged periods (24 h) led to a bed compression attributed to the protein coating of the suppor

ISSN:0006-3592    

DOI:10.1002/bit.260320410

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

年代:1988

数据来源: WILEY

摘要:

AbstractEmpirical equations used so for for computingklain mechanically agitated aerated vessels agree well with the measured dependence ofKlaon the power input of the stirrer and the superficial velocity of the gas. However, they do not fit the dependence ofKlaon the physical properties of the liquid batch. From the data published so far it can be deduced that the equations suitable for the description of the dependence ofkmolaon the liquid physical properties must include some independent variable, which characterizes the rate of coalescence of the bubbles. About 400 experimental values ofKlawere compared with those calculated from different relations. This comparison shows that the rate of coalescence for the aqueous electrolyte solutions is well described on the basis of the Gibbs theory of adsorption of the solute in the surface layer of the solution.

ISSN:0006-3592    

DOI:10.1002/bit.260320411

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

年代:1988

数据来源: WILEY