Dynamics modeling of nitrogen compounds in microalgae cells. 2. Chemostat

The work focuses on dynamics modeling of nitrogen compounds in microalgae cells under chemostat conditions. The analysis of classical models (Michaelis–Menten, Monod, Droop), which describe the kinetics of substrate-dependent growth of microalgae, was carried out. Classical models are shown to be applicable provided that the physicochemical parameters of the medium such as temperature, cell irradiation, etc are constant. As an alternative approach, the possibility of using linear splines in kinetics modeling of nitrate absorption by microalgae is shown. For the conditions of the chemostat, particular solutions for the generalized model of the dynamics of nitrogen compounds in the cells of microalgae considered in the first part of the work were obtained, and boundary conditions for the culture growth at unlimited nitrogen were determined. For limited growth, the equation for both the dependence of the specific growth rate on the intracellular nitrogen content, which coincides in form with the Droop model and the dependence of the specific growth rate on the extracellular concentration of nitrogen, which coincides in form with the Monod model were obtained. The species-specific coefficients of the equations such as the maximum specific rate of nitrogen absorption, the maximum specific rate of synthesis of structural components, the maximum content of reserve forms of nitrogen, the minimum share of structural forms of nitrogen in the total cell content were determined.