Carbon fixation using fast-growing autotrophic microorganisms, such as microalgae, provides a very promising strategy for CO2 mitigation, producing high-value products. However, despite being CO2-dependent, high concentrations of CO2 may inhibit microalgae development, which encourages the search for high CO2-tolerant microalgae. Here, screening methods were developed to isolate microalgae from mangroves in Cubatão (SP,Brazil) area. Samples were cultured in photoincubator and microalgae were isolated using plating and successive dilution techniques. The focus of the work is to design an efficient system to select high CO2-tolerant microalgae, provided by gas streams of CO2/N2 with different CO2 compositions (up to 30%), as well as to obtain quantitative physiological parameters by measuring growth kinetics. Preliminary tests, using a commercial microalgae Desmodesmus sp., have validated the system and further tests will be proceeded.