Enhanced growth and lipid production in psychrotolerant Acutodesmus by controlling temperature-dependent nitrogen concentration

During the mass production of microalgal biodiesel in temperate countries, one of the major obstacles is the lower growth in winter. Therefore, a domestic psychrotolerant microalga, Acutodesmus obliquus MR, was isolated, and its growth and lipid productivity were characterized. The optimal nitrogen concentration for growth was 50 mg-N L(-1 )at 10 degrees C, but it increased to over 120 mg-N L-1 at 25 degrees C. Lipid productivity was also higher under lower nitrogen concentrations at 10 degrees C but decreased with increasing nitrogen concentrations. Lipid productivity was optimal under lower nutrient concentrations at 10 degrees C but decreased at higher concentrations. Although the growth rate increased under the mixotrophic mode with higher nitrogen concentrations, lipid productivity was not enhanced due to the decreased lipid content. The quality of fatty acid composition (C16:0, C18:1 and C18:2 > 60%) for biodiesel was improved at low temperature. Since optimum nitrogen concentration shifts depending on temperature in Acutodesmus obliquus MR, nitrogen concentration should be adjusted along the seasonal temperature change to maximize biomass production.