Enhancement effects of ferric ion concentrations on growth and lipid characteristics of freshwater microalga Chlorococcum oleofaciens KF584224.1 for biodiesel production

To elucidate the potential of Chlorococcum oleofaciens KF584224.1, the effects of different ferric ion concentrations (0, 10−7, 10−6, 10−5, 10−4 mol L−1) on growth, lipid accumulation, and fatty acid profile has been studied. The quantity and quality of extracted lipid was also analyzed by gravimetric and gas chromatographic methods, respectively, to evaluate their suitability according to the international standards for biodiesel (ASTM D6751 and EN 14214). An increase in ferric ion concentration up to 10−6 mol L−1 was associated with an increased specific growth rate by 1.83 folds and expanded exponential growth rate by 10 days compared with that in 0 mol L−1 ferric ion concentration. The highest biomass productivity (310.17 ± 2.19 mg L−1 d−1) and lipid productivity (138.81 ± 3.57 mg L−1 d−1) were achieved in culture medium supplemented with 10−6 and 10−5 mol L−1 ferric ion. The proportion of PUFAs and SFAs tends to decrease and increase by enhancing the ferric ion concentration, respectively. Although the quality of biodiesel produced form C. oleofaciens was found to be in accordance with the specifications in the American (ASTM D6751) and European (EN 14214) biodiesel standards, ferric ion supplementation enhanced the lipid characteristics obtained from C. oleofaciens for biodiesel production.