Biomass, lipid productivity and fatty acid composition of fresh water microalga Rhopalosolen saccatus cultivated under phosphorous limited conditions

This study reports the bioprospecting of microalgae as a potential feedstock for biomass and lipid production in the Central Queensland region, Australia. During the dry season of 2010, ninety water samples were collected from a range of water bodies across the Central Queensland region of Australia. These water bodies had pH ranging from of 5.8–8.8, electrical conductivity of 184–2351 μS cm−1 and water temperature between 17 and 21 °C. Strains of Rhopalosolen saccatus, Navicula sp. 1, Nitzschia pusilla and Navicula sp. 2 were identified positive for neutral lipid content. Among the strains R. saccatus had significantly high biomass (1.46 g L−1) and lipid content (0.20 g L−1) compared to other strains when cultivated for 22 d under standard nutrient growth media. When grown under limiting P conditions, biomass and total lipid across the treatments did not vary significantly from the control, although a few fatty acids such as C16:0, C16:1 and C18:3 increased significantly (p ≤ 0.05).The prevalent fatty acids in this study included C22:0 followed by C20:0 and C18:3, in decreasing order of concentrations.The pH varied from 6.84 to 9.87 across the growth trials and there was no significant correlation between pH, biomass, total lipid and P concentrations.