Morphologically Structured Models
In Chapters 2 and 4, we specified the stoichiometry and kinetics for the metabolism of individual cells, and it was assumed that all the cells in a culture have the same metabolism; i.e., the cell population was assumed to be completely homogeneous. This assumption is reasonable for most unicellular bacterial cultures (see also the discussion in Chapter 6), but for yeasts and filamentous microorganisms cellular segregation in the culture may have a serious impact on the overall performance of the culture. Thus in yeast cultures there is a difference in the cellular metabolism of mother and daughter cells (see Section 5.2), and in filamentous microorganisms there is a significant variation in the metabolism of the individual cells in the multicellular structures that make up the filaments (see Section 5.3). To describe these cultures correctly it is necessary to consider a morphological variation of the individual cells. Therefore a metabolic model for each individual morphological form is combined with a model for the population of morphological forms, i.e., a morphologically structured model. The theoretical concepts governing the interactions among different morphological forms of the same strain of a given microorganism can also be used to determine the behavior of so-called mixed populations. A mixed cell population could consist of the wild-type strain and several genetically engineered variants of the microorganism, but heterogeneous cultures of very different microorganisms are also included in the discussion of mixed populations in Section 5.4. In the first section of the chapter, a framework for morphologically structured models will be introduced.
KeywordsSpecific Growth Rate Dilution Rate Morphological Form Apical Compartment Spontaneous Oscillation
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- Bailey, J. E. and Ollis, D. F. (1986). Biochemical Engineering Fundamentals, 2d. ed., McGraw-Hill, New York.Google Scholar
- Bartnicki-Garcia, S. (1973). “Fundamental aspects of hyphal morphogenesis,” Svmp. Soc. Gen. Microbiol. 23, 245–267.Google Scholar
- Bartnicki-Garcia, S. (1990). “Role of vesicles in apical growth and a new mathematical model of hypha morphogenesis,” In Tip Growth in Plant and Fungal Cells, I.B. Heath ed., Academic Press, San Diego.Google Scholar
- Cazzador, L. (1991). “Analysis of oscillations in yeast continuous cultures by a new simplified model,” Bull. Math. Biol. 5, 685–700.Google Scholar
- Cazzador, L. and Mariani, L. (1990). “A two compartment model for the analysis cf spontaneous oscillations in s. cerevisiae, ” Abstract book (European Congress on Biotechnology, Copenhagen) 5, 342.Google Scholar
- Frandsen, S. (1993). Dynamics of Saccharomyces Cerevisiae in Continuous culture, Ph.D. thesis, Technical University of Denmark, Lyngby.Google Scholar
- Matsumura, M., Imanaka, T., Yoshida, T., and Tagushi, H. (1981). “Modelling of Cephalosporin C production and application to fed-batch culture,” J. Ferment. Technol. 59, 115–123.Google Scholar
- Munch, T. (1992). Zellzyklusdynamik von Saccharomyces Cerevisiae in Bioprozessen, Ph.D. thesis, ETH, Zürich.Google Scholar
- Trinci, A. P. J. (1984). “Regulation of hyphal branching and hyphal orientation,” in The Ecology and Physiology of the Fungal Mycelium, D. H. Jennings and A. D. M. Rayner, eds., Cambridge University Press, Cambridge, UK.Google Scholar