Isolation and identification by 18S rDNA sequence of high lipid potential microalgal species for fuel production in Hainan Dao

To exploit indigenous microalgal species with the potential for biodiesel production, 101 algal cultures were isolated from partial waters in Hainan province. Eight cultures were selected based on their high biomass, high lipid content and ease of cultivation, then identified based on morphology and 18S rDNA sequence analysis. These isolates were identified as Tetranephris brasiliensis DL12, Ankistrodesmus gracilis DL25, Ankistrodesmus sp. CJ02, Desmodesmus subspicatus WC01, A. gracilis CJ09, Chlorella vulgaris CJ15, Desmodesmus sp. WC08, Chlorella sorokiniana XS04, respectively. Desmodesmus sp. WC08 reached the highest biomass concentration (2.32 g L−1) with the lipid content of 31.30%. Higher lipid content of 47.90% and 47.39% were gained by A. gracilis CJ09 and C. vulgaris CJ15, respectively. However, C. vulgaris CJ15 and Desmodesmus sp. WC08 had higher lipid productivity (117.37 mg L−1 d−1and 115.73 mg L−1 d−1, respectively) in terms of comprehensive consideration. The fatty acid compositions of these microalgal species were mainly palmitic, palmitoleic, stearic, oleic with GC–MS (gas chromatography–mass spectrometer) analysis. A. gracilis CJ09, T. brasiliensis DL12, A. gracilis DL25 and Desmodesmus sp. WC08 had the higher oleic acid content (over 50% of the total fatty acids) than the others. The results suggest that marine microalgae strain Desmodesmus sp. WC08 can be the most appropriate candidate for producing oil for biodiesel, based on its higher biomass productivity, lipid productivity and fatty acid profile.