Structured segregated models and analysis of self-oscillating yeast continuous cultures

A structured segregated model of budding yeast (Saccharomyces cerevisiae) populations is analysed in order to verify its ability to predict the spontaneous oscillations arising in continuous cultures. To obtain tractable and useful information about the relationships among the metabolic modifications during the cell cycle, the control over division and the occurrence of oscillations, very simple assumptions are considered and added to the model. The cell metabolism has been taken into account by assuming a diversification in the yield coefficient during the cell cycle. Moreover, in the oscillatory range, the cell mass is assumed to be constant at budding and to depend on the limiting substrate concentration at division. For a suitable range of parameter values, sustained oscillations are obtained, which can be compared to the experimental ones.List of Symbols D dilution rate - K_h critical substrate for h - K_s saturation constant - h ratio between size at division and size at budding - h_max maximum h value - h_min minimum h value - s substrate concentration - s_in substrate concentration in the input flow - x budded biomass concentration - y unbudded biomass concentration - Y_x yield coefficient for budded biomass - Y_y yield coefficient for unbudded biomass - specific growth rate - _max maximum specific growth rate