Culture of microalgal strains isolated from natural habitats in Thailand in various enriched media

Six freshwater microalgal strains in the class of Chlorophyceae, including Chlorococcum humicola, Didymocystis bicellularis, Monoraphidium contortum, Oocystis parva, Sphaerocystis sp., and Scenedesmus acutus were isolated from natural habitats in Thailand. The six strains were compared for their biomass yield, lipid content, and lipid productivity in four enriched culture media in batch mode. Significant differences were found across algal strains and culture media. The best strain was found to be C. humicola, which had the highest biomass yield of 0.113 g/l/d (in Kuhl medium), the highest lipid content of 45.94% (in BG-11 medium), and the highest lipid yield of 0.033 g/l/d (in 3NBBM medium). The 3NBBM medium, which has the lowest nitrogen concentration among the four culture media, was considered the optimal culture medium for C. humicola for lipid production. The fatty acid profile of C. humicola was also found to be affected by the culture medium. More oleic acid (C18:1) but less linolenic acid (C18:3) was accumulated in BG-11 and 3NBBM than in Kuhl and N-8 media. Lipid profiles of C. humicola were comparable to palm oil in the percentage of palmitic acid and the total amount of saturated fatty acids; however, C. humicola made more poly-unsaturated fatty acids such as linoleic (C18:2) and linolenic (C18:3) acids than oil palms. Lipids from C. humicola were believed to be acceptable for biodiesel production.