Improvement of lipid production in the marine strains Alexandrium minutum and Heterosigma akashiwo by utilizing abiotic parameters
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Two different strains of microalgae, one raphidophyte and one dinoflagellate, were tested under different abiotic conditions with the goal of enhancing lipid production. Whereas aeration was crucial for biomass production, nitrogen deficiency 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 different conditions did not significantly change the fatty acids profiles of the species analyzed. These profiles consisted of saturated fatty acids (SAFA) and polyunsaturated fatty acids (PUFA) in significant 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 sufficient quantities of microalgal biomass, with high oil content and minimal changes in the fatty acid profile of the strains under consideration.
KeywordsMicroalgae Dinoflagellates Raphidophytes Lipids Biofuel Triacylglycerols
We are grateful to the members of the L′Esfera Ambiental Laboratory, Universitat Autònoma de Barcelona, for their help in gas chromatography analyses. We thank S. Fraga for providing the clonal culture AMP4. We thank L. del Río for help with the experiments, and the Zona Acuarios Experimentales (ZAE) of the ICM-CSIC for the use of their facilities. We gratefully acknowledge the Comisión Nacional de Investigación Ciencia y Tecnología (CONICYT), Chile, for its support of the scholarship “Beca de Gestión Propia,” which finances the PhD studies of C. Fuentes-Grünewald. The work of S. Rossi is supported by the Ramon y Cajal award of the Spanish Ministry of Science and Innovation.
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