Improvement of lipid production in the marine strains Alexandrium minutum and Heterosigma akashiwo by utilizing abiotic parameters

Two diVerent strains of microalgae, one raphidophyte and one dinoXagellate, were tested under diVerent abiotic conditions with the goal of enhancing lipid production. Whereas aeration was crucial for biomass production, nitrogen deWciency and temperature were found to be the main abiotic parameters inducing the high-level cellular accumulation of neutral lipids. Net neutral lipid production and especially triacylglycerol (TAG) per cell were higher in microalgae (>200% in Alexandrium minutum, and 30% in Heterosigma akashiwo) under treatment conditions (25°C; 330 μM NaNO3) than under control conditions (20°C; 880 μM NaNO3). For both algal species, oil production (free fatty acids plus TAG fraction) was also higher under treatment conditions (57 mg L-1 in A. minutum and 323 mg L -1 in H. akashiwo). Despite the increased production and accumulation of lipids in microalgae, the diVerent conditions did not signiWcantly change the fatty acids pro- Wles of the species analyzed. These proWles consisted of saturated fatty acids (SAFA) and polyunsaturated fatty acids (PUFA) in signiWcant proportions. However, during the stationary phase, the concentrations per cell of some PUFAs, especially arachidonic acid (C20:4n6), were higher in treated than in control algae. These results suggest that the adjustment of abiotic parameters is a suitable and one of the cheapest alternatives to obtain suYcient quantities of microalgal biomass, with high oil content and minimal changes in the fatty acid proWle of the strains under consideration. © Society for Industrial Microbiology 2011.