Lipid production enhancement in tropically isolated microalgae by azide and its effect on fatty acid composition

Abstract

Microalgae, as photosynthetic microorganisms, have been referred to as the third generation of biodiesel feedstock due to their ability to accumulate high amounts of lipids in their intracellular bodies. However, the commercialization of microalgal biodiesel is currently not economical due to high production cost. Recently, a novel strategy was found to overcome this issue and, at the same time, boost the accumulation of lipids by the addition of azide to the microalgal culture. Azide was added to study its effect on the growth and accumulation of fatty acids in three strains of tropical microalgae, identified as Acutodesmus obliquus, Desmodesmus maximus, and Chlorella pyrenoidosa, which were isolated from the Hulu Langat River, Selangor, Malaysia. Lipid production of A. obliquus and D. maximus after azide treatment increased by 40 and 20%, respectively. In contrast, the induction of azide led to insignificant lipid accumulation in C. pyrenoidosa, likely because azide targeted the respiration system rather than lipid production, which consequently caused a slight growth retardation. There was a great difference in the types of fatty acids found in azide-treated cells and non-treated cells. In A. obliquus, more saturated fatty acids (SFAs) were found in azide-treated cells, while more polyunsaturated fatty acids (PUFAs) were found in non-treated cells. In C. pyrenoidosa, the induction of lipid accumulation by azide led to the formation of more SFAs and PUFAs. For D. maximus, the cells synthesized more monounsaturated fatty acids (MUFAs) in both azide-treated and untreated media but azide treatment increased an insignificant amount of PUFAs.