Investigations on microalgal oil production from Arthrospira platensis: towards more sustainable biodiesel production

Abstract

Microalgae have emerged as one of the most promising sources for biodiesel production. Arthrospira platensis (Spirulina) is known for its nutritional benefits with very low lipid content. However, among all other algae, spirulina is the most easy to cultivate due to its inherent resistance to contamination and environmental changes. The presented work aims to determine the best culture medium to achieve an optimum lipid content for microalgae in view of a subsequent exploration for biodiesel production. This was conducted by means of a two step microalgal oil extraction followed by a conventional acid-catalysed esterification of the released fatty acids. Algal growth, biomass and lipid content were compared for Spirulina grown under six different culture media. 1) culture medium of complete nutrition (CONTROL); 2) nitrogen and phosphorus-deprived [NP(-)]; 3) nitrogen-deprived [N(-)]; 4) phosphorus-deprived [P(-)]; 5) nitrogen and phosphorus-limited [NPL] and; 6) nitrogen-deprived and phosphorus-limited [N(-)PL]. With the minimum possible dried biomass (0.4780 g L⁻¹), the largest lipid content (ca. 20%) was achieved in spirulina grown under nitrogen-deprived and phosporous-limited conditions [N(-)PL]. Dried biomass from Spirulina grown under two opposite culture media: complete nutrition [CONTROL]; and nitrogen and phosphorous deprived [NP(-)], were utilised for biodiesel preparation after oil extraction. A crude biodiesel yield of 40% and 42%, with a FAME content of 69% and 55% were obtained for CONTROL and NP(-) samples, respectively. Interestingly, the nutrient condition of Spirulina did influence biodiesel yields but not significantly their FAME compositions, which comprised of mostly C16:0 and C18:2, similar to that of conventional biodiesel.