Continuous culture, feedback control and auxostats

Fraleigh, Steven P.

doi:10.1016/0167-7799(89)90027-9

Cited by 32 publications

(11 citation statements)

References 8 publications

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“…A number of factors including nutrient contents, product and by-product concentration, osmotic pressure, pH, dissolved oxygen, viscosity and antimicrobial constituents affect the growth and the survival of microorganisms in a culture [19]. Continuous cultivation of microorganisms, compared to batch operation, offers the advantages of constant environmental conditions for biological systems, which can be highly sensitive to process variations [9].…”

Section: Introductionmentioning

confidence: 99%

Application of an improved continuous parallel shaken bioreactor system for three microbial model systems

Akgün

Müller

Engmann

et al. 2008

Bioprocess Biosyst Eng

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A continuous parallel shaken bioreactor system, combining the advantages of shaken bioreactors with the advantages of continuous fermentation, was specifically manufactured from quartz glass and provides a geometric accuracy of <1 mm. Two different model systems (facultative anaerobic bacterium C. glutamicum, and Crabtree-negative yeast P. stipitis), whose growth behaviour and metabolite formation are affected by dilution rate and oxygen availability, were studied. The transition from non-oxygen to limited conditions as function of the dilution rate could precisely be predicted applying the approach described by Maier et al. (Biochem Eng J 17:155-167, 2004). In addition, the Crabtree-positive yeast S. cerevisiae was simultaneously studied in the continuous parallel shaken bioreactor system and in a conventional 1-L bioreactor, for comparison. Essentially the same results were obtained in both types of bioreactors. However, many more reading points were obtained with the parallel shaken bioreactor system in the same time at much lower consumption of culture media.

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Section: Introductionmentioning

confidence: 99%

Application of an improved continuous parallel shaken bioreactor system for three microbial model systems

Akgün

Müller

Engmann

et al. 2008

Bioprocess Biosyst Eng

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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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“…The pH-auxostat as a nutrient-sufficient continuous culture (Martin and Hempfling 1976;Fraleigh et al 1989) allows measurement of the influence of added substances directly by a change in the dilution rate ( = growth rate) in a similar way to the above simpler method, but with better accuracy and reproducibility (Larsson and Enfors 1990). In the present paper the action of the three products of clostridial glycerol fermentation is analysed by adding them separately to a culture that grows near its maximal specific rate.…”

Section: Introductionmentioning

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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Continuous culture, feedback control and auxostats

Cited by 32 publications

References 8 publications

Application of an improved continuous parallel shaken bioreactor system for three microbial model systems

Application of an improved continuous parallel shaken bioreactor system for three microbial model systems

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

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

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