Competition in a pHauxostat

Schulthess, R. von; Bungay, Henry R.; Fraleigh, Steven P.

doi:10.1007/bf01022422

Cited by 5 publications

(3 citation statements)

References 3 publications

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“…An important, and now perhaps more popular, alternative to the optical turbidostat is the pHauxostat (Martin & Hempfling, 1976;Stouthamer & Bettenhaussen, 1976;Oltmann et al, 1978;MacBean et al, 1979;Bungay et al, 1981 ;Rice & Hempfling, 1985;Minkevich et al, 1989;Fraleigh et al, 1989Fraleigh et al, , 1990von Schulthess et al, 1990), in which the growth-associated microbial production of acid (or, in principle, base) causes a change in pH which is returned to its set-point not by the addition of alkali per se but by the addition of a more alkaline nutrient medium; the biomass level in the steady state is then determined by the buffering power of the medium (whilst the dilution rate again corresponds to a value approaching pmax for the medium and conditions employed). The pHauxostat is relatively straightforward to implement, but has the disadvantages that (i) the biomass level is still set indirectly, (ii) there is a limit to the range of buffering powers which can be provided, and (iii) the cells must actually change the external pH by a substantial amount as a result of their catabolic activities [which is not always the case (Watson, 1972;Firstenberg-Eden & Eden, 1984)l.…”

Section: Aberystwythmentioning

confidence: 99%

The permittistat: a novel type of turbidostat

Markx

Davey

Kell

1991

Journal of General Microbiology

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Baker's yeast was grown in a novel type of turbidostat in which the steady-state biomass level was controlled not by the optical turbidity but by the dielectric permittivity of the suspension at appropriate radio frequencies. Dry weight, fresh weight, the optical density at 600 nm, percentage viability (from methylene blue staining), bud count and ethanol concentration were measured off-line and the cell size distribution was recorded using flow cytometry. Any changes in the physiological properties of the yeast had a negligible effect on the ratio between the permittivity set (and measured) and the steady-state dry weight, fresh weight or optical density of the cultures. The permittistat was found to provide an extremely convenient means for carrying out turbidostatic culture.

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Section: Aberystwythmentioning

confidence: 99%

The permittistat: a novel type of turbidostat

Markx

Davey

Kell

1991

Journal of General Microbiology

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“…The implementation shown in Figure 5 is more complicated than BOICS in that it requires the control of two pumps, but it may turn out to have other advantages. In view of the above discussion, the CO 2 -stat could be replaced by a turbidostat, pHauxostat (Martin and Hempfling, 1976;Schulthess et al, 1990), permittistat (Markx et al, 1991), or nutristat (Kleman et al, 1991;Mori et al, 1983). In the latter case, a nutrient concentration is directly measured and controlled.…”

Section: Interpretation Of Boicsmentioning

confidence: 97%

Analysis of a continuous-culture technique for the selection of mutants tolerant to extreme environmental stress

Lane

Oliver

Butler

1999

Biotechnol. Bioeng.

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“…Continuing the theme of comparative 'growth-omics', the growth rates of yeasts are significantly slower than those of bacteria, the record (in terms of rate of biomass doubling) apparently being Kluyveromyces marxianus with a doubling time of some 52 min [498] (a growth rate approximately twice that of S. cerevisiae [541,[545][546][547]). This was achieved [498] via a different kind of growth rate selection in a kind of 'turbidostat' called a pHauxostat [548][549][550]).…”

Section: Growth Rate Engineeringmentioning

confidence: 99%

Intelligent host engineering for metabolic flux optimisation in biotechnology

Munro

Kell

2021

Biochemical Journal

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Optimising the function of a protein of length N amino acids by directed evolution involves navigating a ‘search space’ of possible sequences of some 20N. Optimising the expression levels of P proteins that materially affect host performance, each of which might also take 20 (logarithmically spaced) values, implies a similar search space of 20P. In this combinatorial sense, then, the problems of directed protein evolution and of host engineering are broadly equivalent. In practice, however, they have different means for avoiding the inevitable difficulties of implementation. The spare capacity exhibited in metabolic networks implies that host engineering may admit substantial increases in flux to targets of interest. Thus, we rehearse the relevant issues for those wishing to understand and exploit those modern genome-wide host engineering tools and thinking that have been designed and developed to optimise fluxes towards desirable products in biotechnological processes, with a focus on microbial systems. The aim throughput is ‘making such biology predictable’. Strategies have been aimed at both transcription and translation, especially for regulatory processes that can affect multiple targets. However, because there is a limit on how much protein a cell can produce, increasing kcat in selected targets may be a better strategy than increasing protein expression levels for optimal host engineering.

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Competition in a pHauxostat

Cited by 5 publications

References 3 publications

The permittistat: a novel type of turbidostat

The permittistat: a novel type of turbidostat

Analysis of a continuous-culture technique for the selection of mutants tolerant to extreme environmental stress

Intelligent host engineering for metabolic flux optimisation in biotechnology

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