Structured modeling of a microbial system: III. Growth on mixed substrates

Nikolajsen, K.; Nielsen, Jens; Villadsen, John

doi:10.1002/bit.260380104

Cited by 42 publications

(21 citation statements)

References 6 publications

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“…This allows testing the model on experiments with transient operating conditions. 21 The model structure is open ended and it can rather easily be extended to describe more complex systems.…”

Section: Discussionmentioning

confidence: 99%

Structured modeling of a microbial system: I. A theoretical study of lactic acid fermentation

Nielsen

Nikolajsen

Villadsen

1991

Biotech & Bioengineering

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Most fermentation models presented in the literature are unstructured, i.e., the biomass composition is assumed constant during all operating conditions. These models are unable to simulate experiments carried out at widely different operating conditions. It is therefore interesting to examine simple structured models where knowledge of the cell physiology is taken into account in the modeling phase. In this article, a simple structured model is presented. The model is based on experimental work with the lactic acid bacteria Streptococcus cremoris, but due to the similarities in basic metabolism for many microorganisms it is applicable also for other fermentation system. The basic assumption in the model is that the biomass can be divided into two parts (compartments)-an active part and a mainly inactive structural part. The size of the active part has a pivotal role in the model.

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Section: Discussionmentioning

confidence: 99%

Structured modeling of a microbial system: I. A theoretical study of lactic acid fermentation

Nielsen

Nikolajsen

Villadsen

1991

Biotech & Bioengineering

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“…While this is obviously true of natural substrates, often synthetic media also contain complementary substrates to achieve good growth and productivity. 10,11 However, no investigation has yet been reported on the effect of mixing in a bioreactor on the simultaneous rates of consumption of two or more substrates. The present communication analyses this problem for two substrates through a cybernetic approach.…”

Section: Notationmentioning

confidence: 98%

On the improvement of bacterial growth on complementary substrates by partial segregration in the broth

Patnaik

2000

J. Chem. Technol. Biotechnol.

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Previous studies have shown that when two species compete for the same substrate, a controlled degree of segregation in a bioreactor favours growth of the desired species. That concept has been extended to the growth of bacteria on a mixture of two substrates for one of which the organism has a natural preference. However, using the example of Escherichia coli cultivated in a medium containing glucose and fumarate, it has been shown that, while the physiological preference for glucose is maintained, incomplete macromixing promotes growth and enables better utilisation of both substrates. While the preferred substrate (glucose) is consumed ®rst in a perfectly mixed reactor, imperfect mixing allows both substrates to be utilised simultaneously, at different rates. By dividing the broth conceptually into an inoculated region and a non-inoculated region, it is seen that cell growth is favoured by an initial period of good mixing followed by poor mixing in the non-inoculated region.

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“…Models for the sequential uptake of different substrates, known as diauxic or triauxic growth, have been proposed since last decade (Nielsen and Villadsen, 1992) in which compartment models (Nikolajsen et al, 1991) or a cybernetic view of the cell for optimizing biomass production (Dhurjati et al, 1985) were used. These models were based on the calculation of enzyme levels, of which each level is specific for a certain substrates.…”

Section: Modelling Of Mixed Substrate Kinetics Of Crabtree-positive Ymentioning

confidence: 99%

Quantitative analysis of the regulation scheme of invertase expression in Saccharomyces cerevisiae

Herwig

Doerries

Marison

et al. 2001

Biotech & Bioengineering

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In Saccharomyces cerevisiae, the expression of invertase, which is the hydrolyzing enzyme of sucrose, is controlled by the presence of monosaccharides, such as glucose and fructose, and referred to as carbon catabolite repression. To date, efforts have been made to identify the mechanism by which cells sense extracellular monosaccharide concentrations and trigger the genes involved in the repression pathway. The aim of the present work was to quantitatively investigate the cellular regulation of invertase expression in the wild-type strain S. cerevisiae CEN.PK113-7D during batch growth containing mixed sugar substrates under different initial conditions. Because of the high frequency and accurate online analysis of multiple components, a tight control of invertase expression could be observed, and threshold concentrations of the monosaccharides for derepression could be determined to 0.5 gl(-1) for glucose and 2 gl(-1) for fructose. Also, the existence of a hitherto undescribed regulatory state, in which cells regulate invertase expression very precisely and operate over long periods at monosaccharide concentrations lower than the above thresholds, could be demonstrated. All experimental observations could be summarized in a formulation of the cellular regulation scheme of invertase expression. A simple kinetic model could show that the regulation scheme explains the observed behavior very well. Additionally, the model was able to explain consequences of the regulation on the global metabolism.

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Structured modeling of a microbial system: III. Growth on mixed substrates

Cited by 42 publications

References 6 publications

Structured modeling of a microbial system: I. A theoretical study of lactic acid fermentation

Structured modeling of a microbial system: I. A theoretical study of lactic acid fermentation

On the improvement of bacterial growth on complementary substrates by partial segregration in the broth

Quantitative analysis of the regulation scheme of invertase expression in Saccharomyces cerevisiae

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