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Showing papers by "Douglas B. Kell published in 1986"


01 Jan 1986
TL;DR: The metabolic control theory developed by Kacser, Burns, Heinrich and Rapoport can provide a rational and quantitative basis for the description and improvement of such processes.
Abstract: 1. SUMMARY Many areas of microbiology and biotechnology are directly concerned with the isolation, study or engineering of cells capable of (over)producing metabolites of commercial significance. Yet the study, production or improvement of such strains has often been at best semi-empirical. The metabolic control theory developed by Kacser, Burns, Heinrich and Rapoport can provide a rational and quantitative basis for the description and improvement of such processes.

171 citations


Journal ArticleDOI
TL;DR: The metabolic control theory developed by Kacser, Burns, Heinrich and Rapoport can provide a rational and quantitative basis for the description and improvement of such processes as discussed by the authors. But the study, production or improvement of these strains has often been at best semi-empirical.
Abstract: Many areas of microbiology and biotechnology are directly concerned with the isolation, study or engineering of cells capable of (over)producing metabolites of commercial significance. Yet the study, production or improvement of such strains has often been at best semi-empirical. The metabolic control theory developed by Kacser, Burns, Heinrich and Rapoport can provide a rational and quantitative basis for the description and improvement of such processes.

170 citations


Journal ArticleDOI
TL;DR: An extension of the metabolic control theory of Kaeser, Burns, Heinrich and Rapoport allows one rationally to identify optimal strategies for the improvement of microbial processes.

49 citations


Journal ArticleDOI
TL;DR: The reduction of proline by Clostridium sporogenes NCIB8053 is coupled to transmembrane proton translocation in an uncoupler-sensitive fashion (and might therefore conserve free energy).
Abstract: The reduction of proline by Clostridium sporogenes NCIB8053 is coupled to transmembrane proton translocation in an uncoupler-sensitive fashion (and might therefore conserve free energy). This finding serves to explain the increase in the growth yield of this organism when proline is added to a defined growth medium containing glucose as the catabolic substrate.

38 citations


Journal ArticleDOI
TL;DR: The fermentation end products of Clostridiumpasteurianum ATCC 6013 are normally acetic and butyric acids as discussed by the authors, however, when grown in media of high sugar content, significant quantities of solvents (acetone, butanol and ethanol) were produced.
Abstract: The fermentation end products ofClostridiumpasteurianum ATCC 6013 are normally acetic and butyric acids. When grown in media of high sugar content however, significant quantities of solvents (acetone, butanol and ethanol) were produced. Solvent production was not stimulated by added acetic and butyric acids, nor was the effect due to a low water activity of the mediumperse.

23 citations


Book ChapterDOI
TL;DR: An overview and critical evaluation of the techniques of localized protonic coupling and the harmonization of double inhibitor-titration protocols within the framework of metabolic control theory might constitute a particularly rigorous and rewarding approach to this problem.
Abstract: Publisher Summary This chapter provides an overview and critical evaluation of the techniques of localized protonic coupling. The double inhibitor-titration approach provides strong evidence for localized coupling or energy transfer domains. The experiments involved are technically relatively straightforward, requiring only the measurement of the rates of phosphorylation. The uncoupler/energy transfer inhibitor experiments in which the observation that one ionophore per thylakoid or per chromatophore cause a certain amount of uncoupling is used in support of the delocalized chemiosmotic coupling concept. The harmonization of double inhibitor-titration protocols within the framework of metabolic control theory might constitute a particularly rigorous and rewarding approach to this problem. Respiration-driven H + translocation method is described in the chapter. The translocation of protons and sometimes of other ions is measured with ion-selective electrodes and calibrated with anaerobic standard solutions. Ion-distribution methods are widely used to measure the chemiosmotic membrane potential, which dominates the protonmotive force (pmf). The rate of transmembrane field-driven secondary ion transport is a function of both any transmembrane potential and the native permeability coefficient.

22 citations


Journal ArticleDOI
TL;DR: The ratio of the conductivity of a suspension of gel-immobilised cells to that of the suspending medium can be used to give a rapid and convenient assessment of the amount of microbial biomass present.
Abstract: The problem of obtaining a rapid estimate of the microbial content of an immobilised cell suspension is addressed. The “low-frequency” conductivity of free-living cell suspensions of Clostridium pasteurianum is lower than that of the medium in which they are suspended, by an amount conforming to the Bruggeman relation. The conductivity of the cell wall makes a negligible contribution to the measured conductivity under the conditions used. Calcium alginate beads (lacking microbial cells) lower the conductivity of a solution with which they have been equilibrated by an extent which is a function of the concentration of alginate gel used in forming the beads. When this is taken into account, the ratio of the conductivity of a suspension of gel-immobilised cells to that of the suspending medium can be used to give a rapid and convenient assessment of the amount of microbial biomass present.

19 citations


Journal ArticleDOI
TL;DR: In this paper, the dielectric properties of chloroplast thylakoids have been determined in the range 10 Hz to 13 MHz and it was shown that the α-dispersion is not caused solely by the unrestricted tangential relaxation of the ions of the diffuse double layer.

9 citations


Journal ArticleDOI
01 Jan 1986
TL;DR: In this article, the first stage of the two-stage cell electrofusion technique involves the dielectrophoretic apposition, in an AC field, of protoplasts suspended in a medium of relatively low specific conductivity.
Abstract: The first stage of the two-stage cell electrofusion technique involves the dielectrophoretic apposition, in an AC field, of protoplasts suspended in a medium of relatively low specific conductivity. A frequency at which the maximum dielectrophoretic force is exerted is given by the characteristic frequency for the dielectric relaxation by a Maxwell-Wagner type of mechanism. We provide a nomograph for the rapid calculation of this frequency.

3 citations



Journal ArticleDOI
TL;DR: The eubacterial plasma membrane, in common with other biological membranes, is now thought generally to be organized as a 'fluid mosaic' of proteins and protein complexes, dispersed in, on and through a 'sea· of phospholipid molecules arranged as a bilayer.
Abstract: The eubacterial plasma membrane, in common with other biological membranes, is now thought generally to be organized as a 'fluid mosaic' of proteins and protein complexes, dispersed in, on and through a 'sea· of phospholipid molecules arranged as a bilayer. Our attention is therefore directed to more quantitative questions, of the form "How fluid?" and "What sort of a mosaic?". In other words, how fast are the hydrodynamically constrained lateral mobilities of prokaryotic membrane proteins. and to what extent is their 'instantaneous' distribution random (Kell, 1984a)? As a first approach, and from a biophysical standpoint. it is simplest to consider a 'model' system (Saffman & Delbriick. 1975; Kell & Harris. 1985a,h) consisting of a spherical shell (radius r) of phospholipid bilayer, of thickness hand 'average' viscosity II· containing cylindrical membrane protein complexes of radius a, the whole separating aqueous phases of viscosity 11'. If we treat the proteins as 'hard' cylinders (i.e. ignoring 'boundary' lipids and longrange intercomplex forces) which take up a negligible area fraction of the membrane, we may relate the membrane protein translational diffusion coefficient D to the vesicle radius and to the (exponential) relaxation time r that a protein (complex) inserted at a given position takes to adopt a 'random' position on the vesicle surface, according to the equation (Huang. 1973: Sowers & Hackenbrock, 1981):

Book ChapterDOI
01 Jan 1986
TL;DR: A recurrent question, which dates from the very origins of modern biochemistry itself, and which constitutes a major theme of the present conference, concerns the degree of relatedness between the organization and activities of the enzymes of cellular energy metabolism in vivo and their behavior in vitro.
Abstract: A recurrent question, which dates from the very origins of modern biochemistry itself (see Schlenk, 1985), and which constitutes a major theme of the present conference, concerns the degree of relatedness between the organization and activities of the enzymes of cellular energy metabolism in vivo and their behavior in vitro. At one level, two extreme types of viewpoint, which we may refer to as “holistic” and “reductionist”, may be discerned.