CO 2 utilization in the production of biomass and biocompounds by three different microalgae.

The atmospheric CO ₂ increase is considered the main cause of global warming. Microalgae are photosynthetic microorganisms that can help in CO ₂ mitigation and at the same time produce value-added compounds. In this study, Scenedesmus obliquus , Chlorella vulgaris , and Chlorella protothecoides were cultivated under 0.035 (air), 5 and 10% (v/v) of CO ₂ concentrations in air to evaluate the performance of the microalgae in terms of kinetic growth parameters, theoretical CO ₂ biofixation rate, and biomass composition. Among the microalgae studied, S. obliquus presented the highest values of specific growth rate ( μ = 1.28 d ^-1 ), maximum productivities ( P _max = 0.28 g L ^-1 d ^-1 ), and theoretical CO ₂ biofixation rates (0.56 g L ^-1 d ^-1 ) at 10% CO ₂ . The highest oil content was found at 5% CO ₂ , and the fatty acid profile was not influenced by the concentration of CO ₂ in the inflow gas mixture and was in compliance with EN 14214, being suitable for biodiesel purposes. The impact of the CO ₂ on S. obliquus cells' viability/cell membrane integrity evaluated by the in-line flow cytometry is quite innovative and fast, and revealed that 86.4% of the cells were damaged/permeabilized in cultures without the addition of CO ₂ .
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