Microalgae Growth and Lipid Production in a Vertical Flat-Plate Photobioreactor: Mechanistic Model Development

Abstract

Energy production via extracted lipids from microalgae has emerged as a promising alternative to fossil fuels. To optimize microalgae biomass production in photobioreactors, identification of optimal operating conditions, optimization of the microalgae production processes, and quantification of fundamental biochemical responses to the environmental factors are the most significant challenges. These need to be addressed for microalgae biomass productions to become economically feasible. For that, this study developed a mechanistic model of microalgal lipid production with respect to environmental and growth conditions, such as photosynthetic photon flux density (PPFFD), essential nutrients, temperature, and CO₂ availability. The main objective of this mechanistic model was to identify nutrient and light conditions that optimize the lipid synthesis in flat-plate photobioreactors with metal halide lamps. In this model, mass balance, quantum mechanics, and soichiometry were taken into account to simulate microalgae biomass production and chemical conversion of light energy into lipids. Mathematical expressions of various fundamental biological and physiological processes governing lipid productivity were determined and integrated into the model to study their complex interactions and to predict biomass, protein, carbohydrate, and lipid productivities. Simulations were compared with actual data for Nannochloropsis salina culture grown the four automated and controlled environment photobioreactors (FACE 4) located at Texas Agrilife Research Center for model calibration and validation.