Growth and Lipid Accumulation in Isolated Microalgae Strains from Vietnamese Waterbodies for Biodiesel Production

Microalgae are promising for biodiesel production due to their lipid content, but research in Vietnam remains limited despite its favourable climate and diverse native strains. This study evaluates the growth, lipid accumulation, and biodiesel potential of seven microalgal strains isolated from various regions in Vietnam. The strains were cultured under controlled conditions (26 ± 1°C, 120 µmol photons m⁻² s⁻¹, 12:12 h light:dark cycle), and total lipids were extracted using a modified Bligh and Dyer method. Fourier-transform infrared (FTIR) spectroscopy was used to identify functional groups in the fatty acid methyl esters (FAME) derived from each strain. High biomass and lipid productivities were observed in Chaetoceros sp. TA24 and Chlorella vulgaris HB, with biomass productivities of 45.19 ± 2.31 and 31.85 ± 0.73 mg L⁻¹ d⁻¹, and lipid productivities of 3.59 ± 0.25 and 3.21 ± 0.01 mg L⁻¹ d⁻¹, respectively. The lipid profiles of the studied strains were dominated by either saturated fatty acids (SFAs) or polyunsaturated fatty acids (PUFAs). Scenedesmus sp. SCE, Scenedesmus sp.SA, and C. vulgaris CNA accumulated PUFAs in the range of 52.78–62.57% of total lipids, equivalent to 3.61–6.20% of dry weight (dw). In contrast, the remaining strains predominantly produced SFAs, accounting for 60.48–95.77% of total lipids or 1.55–6.59% dw. From the obtained lipid composition, different properties of the potential biodiesel products were also estimated and compared with popular standard specifications for biodiesel. The cetane numbers of biodiesels derived from the studied microalgal strains ranged from 51.64 ± 0.08 to 61.51 ± 0.21, while kinematic viscosity values varied between 4.14 ± 0.01 and 5.08 ± 0.02 mm² s⁻¹, meeting all referenced standard requirements. Chaetoceros sp.TA24 and Chlorella vulgaris HB demonstrated strong potential for biodiesel production due to their high biomass productivity, lipid accumulation, and favorable biodiesel properties. These findings provide a basis for the large-scale production of biodiesel from native microalgae in tropical regions such as Vietnam. Further studies should focus on optimization of the culturing conditions, especially at large scale cultivation systems for enhancing biomass growth and lipid productivity or obtaining desired lipid composition or improving the biodiesel properties via blending with other fuels.