Aerobic formation of ethanol by Saccharomyces cerevisiae in a computerized pHauxostat

Fraleigh, Steven P.; Bungay, Henry R.; Clesceri, Lenore S.

doi:10.1016/0168-1656(90)90131-t

Cited by 10 publications

(10 citation statements)

References 12 publications

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“…The relationships between the growth parameters in a pH-auxostat have been repeatedly formulated (Martin and Hempfling 1976;Biittner et al 1986;Fraleigh et al 1990). While the growth rate under steady-state conditions is normally near its maximum, the cell density can be determined by the buffering capacity of the medium.…”

Section: Methodsmentioning

confidence: 99%

Glycerol fermentation of 1,3-propanediol by Clostridium butyricum. Measurement of product inhibition by use of a pH-auxostat

Biebl¹

1991

Appl Microbiol Biotechnol

135

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The fermentation of glycerol to 1,3-propanediol, acetate, and butyrate by Clostridium butyricum was studied with respect to growth inhibition by the accumulating products. The clostridia were grown in a pHauxostat culture at low cell density and product concentration and near maximum growth rate. The products were then added individually to the medium in increasing concentrations and the resulting depression of growth rate was used as a quantitative estimate of product inhibition. Under these conditions growth was totally inhibited at concentrations of 60 g/l for 1,3-propanediol, 27 g/1 for acetic acid and 19 g/1 for butyric acid at pH 6.5. Appreciable inhibition by glycerol was found only above a concentration of 80 g/l. In a pH-auxostat without added products but with high cell density as well as in batch cultures the product proportions were different. The 1,3-propanediol concentration may approach the value of complete inhibition while the concentrations of acetic and butyric acids remained below these values by at least one order of magnitude. It was therefore concluded that 1,3-propanediol is the first range inhibitor in this fermentation.

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Section: Methodsmentioning

confidence: 99%

Glycerol fermentation of 1,3-propanediol by Clostridium butyricum. Measurement of product inhibition by use of a pH-auxostat

Biebl¹

1991

Appl Microbiol Biotechnol

135

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“…Northrop & Kunitz, 1957;Bryson, 1958;Munson & Bridges, 1964;Munson, 1970;Kubitschek, 1974;Harder et al, 1977, James, 1978Brown & Oliver, 1982;Dykhuizen & Hartl, 1983;Fraleigh et al, 1989). Turbidostats and chemostats put selection pressures on the organism that is under study, thus selecting for those best adapted to the (artificial) environment.…”

Section: Discussionmentioning

confidence: 99%

“…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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“…During several decades, the major ®eld for the applications of the pHauxostat technique has been related to dairy industry [3,12,21,22]. Then, it has been used to investigate population selection [5,7,11], growth and physiology of bacteria [9], yeasts [6], and ®lamentous fungi [24] at l max , aerobic ethanol production [6], production of acetone and butanol [26], and product inhibition [1,6], etc. The principle of a pH-auxostat is that the pH-change caused by cell growth is used to control the medium in¯ow so that it brings the pH back to the setpoint.…”

Section: Introductionmentioning

confidence: 99%

Modelling of aerobic growth of Saccharomyces cerevisiae in a pH-auxostat

Pham

Larsson

Enfors

1999

Bioprocess Engineering

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A model for growth and over¯ow metabolism of Saccharomyces cerevisiae was applied to simulate continuous cultivations in a pH-auxostat. The concentrations of glucose, biomass and ethanol are controlled by the¯ow ratio r between fresh medium and titrant solution, both of which are pH-regulated. A critical value of r could be derived, below which the culture becomes substrate depleted, resulting in a stop-¯ow condition with retained biomass but without growth. At r-values slightly above the critical value the pH-auxostat is substrate limited and unstable. Further increase of the r value results in a stable continuous culture growing at l max . Thus, the pH-auxostat complements the chemostat in the growth range at or close to l max . Even at l max conditions, the ethanol concentration can be controlled at a low level.

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Aerobic formation of ethanol by Saccharomyces cerevisiae in a computerized pHauxostat

Cited by 10 publications

References 12 publications

Glycerol fermentation of 1,3-propanediol by Clostridium butyricum. Measurement of product inhibition by use of a pH-auxostat

Glycerol fermentation of 1,3-propanediol by Clostridium butyricum. Measurement of product inhibition by use of a pH-auxostat

The permittistat: a novel type of turbidostat

Modelling of aerobic growth of Saccharomyces cerevisiae in a pH-auxostat

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