Effective scale-up of microalgae cultures in photobioreactors is often limited by low biomass productivity. Even though mixotrophic cultivation may be an effective solution, oxygen balance and concentration gradients are crucial aspects for optimization which have scarcely been investigated. Thus, this Thesis describes the improvement of a model that predicts concentration profiles of substrate, oxygen, carbon dioxide and inert gases in a biphasic tubular photobioreactor for Galdieria sulphuraria. The model can be effectively employed to simulate the reactor with constant light input or real daylight irradiance data. Three different control strategies have been integrated into the model for comparisons. All the Proportional-Integral-Derivative (PID) control logics, that have been designed and tested in silico, resulted in a favorable response of the system in both constant and real light regime, also preventing anoxic conditions in the reactor.