Screening of efficient microalgae strains isolated from Tunisian ecosystems: Assessment of algal growth rate and added-value bioproducts for biorefinery applications

Microalgae are highly diverse organisms with significant applications in the production of high-value molecules and biodiesel from microalgae rich in oils. In this study, our main objectives were to evaluate the potential applications of four isolated microalgae strains, namely Scenedesmus sp., Nannochloris sp.sp., Oscillatoria sp.sp., and Amphora sp.sp., which were selected from the natural environment. These strains were batch cultured, and their growth was monitored. We determined the content of chlorophyll a, carotenoids, and lipids, and analyzed the fatty acid profile of each cultivated strain to assess their lipid potential for biodiesel production. Our findings revealed that these strains exhibited high biomass production, ranging from 3000 mg. L−1 for Amphora sp.sp. to 3800 mg. L−1 for Oscillatoria sp.sp. Notably, Oscillatoria sp.sp. and Scenedesmus sp.sp. were found to be the richest in saturated fatty acids, with 10.68% and 9.36% of dry cell weight, respectively, suggesting their potential use in the production of biodiesel from microalgal oils with possibility of blending with other oils feedstock to improve biodiesel final quality. Furthermore, our results showed that the Nannochloris sp.sp. strain could be cultivated to extract pigments for various applications, as it exhibited high levels of chlorophyll a (38.43 mg. L−1) and carotenoids (4.153 μg. mL−1).