In order to viably scale up the microalgae based technology for CO2 capture and biofuels production, suitable mathematical models should be developed. In particular, since the potential exploitation of flue gases as carbon source is one of the main targets of this technology, the effects resulting from such operating mode on microalgae growth, i.e. low pH values and high dissolved concentration of CO2, should be properly simulated. Along these lines, this work addresses a novel mathematical model of the growth of Chlorella vulgaris in semi-batch photobioreactors fed with pure CO2 (100% v/v). In particular, the proposed model simulates temporal evolution of cells, light intensity and nutrients concentration within the growth medium as well as carbon dioxide and oxygen concentration in the liquid and gas phase. Moreover, by taking advantage of comprehensive kinetics and considering the ion speciation phenomena taking place, the model is able to quantitatively describe the dynamics of pH evolution and its effect on microalgae growth. The adjustable parameters of the proposed model are fitted against experimental data obtained when starting from a specific set of initial concentration of nutrients in the growth medium. Then, the reliability of the mathematical model is successfully tested through the prediction of the temporal evolution of microalgae concentration and pH when using different initial concentrations of nutrients. Thus, the proposed model might represent a useful tool to develop suitable control and optimization strategies to improve microalgal cultures fed with high concentration of CO2. (C) 2012 Elsevier B.V. All rights reserved.