Two-Component Model of Microalgae Growth in the Turbidostat

The paper focuses on the study of light influence mechanisms on microalgae culture growth in the turbidostat. The method of turbidostat culture provides the same light conditions for all cells, stabilization of their biochemical composition, as well as the constancy of all physicochemical factors of the environment. The main approaches and principles of modeling the microalgae culture growth are presented. Modern models are shown to be based on classical concepts of considering cell biomass as the sum of two or more compounds. The use of two-component models for microalgae is due to both photochemical and enzymatic processes of biosynthesis of cell structures from mineral substances due to the energy of high-potential forms of macroergs. The proposed mathematical model is represented by a system of two differential equations describing the synthesis of reserve biomass compounds at the expense of light and biosynthesis of structural components from reserve ones. The model takes into account that a part of the reserve compounds is spent on replenishing the pool of macroergs, and a part of the structural component can be converted into a reserve one. The rates of synthesis of structural and reserve forms of biomass are given by linear splines and expressed in terms of the reduced fluxes of the energy or plastic substrate. The model was verified on the experimental data of the chlorophyllostat culture Tetraselmis viridis. It is shown that the light curve of T. viridis is characterized by a double change in the limiting factor and can be divided into a region of metabolic, light limiting and a region of saturation. A decrease in the specific growth rate is related to a decrease in the efficiency of light energy conversion.