Growth and Lipid Production of Ankistrodesmus Sp. IFRPD 1061 Under Mixotrophic Culture Condition: Effect of Sodium Acetate Concentration and Period Addition of Sodium Acetate in an Open Pond

Microalgae with increased amount of biomass and lipid yield are crucial for biodiesel production. Mixotrophic cultivation has prominence for increasing the micro-algal cell concentration and hence the volumetric productivity owing to independent utilization of both the photo-assimilation of CO₂ and oxidative assimilation of organic carbon sources. In this study, Ankistrodesmus sp. IFRPD 1061 was examined under various concentrations of sodium acetate for concentration and productivity of biomass and lipid, lipid contents (LCs), and fatty acid profiles. The optimum condition was obtained at Day 21 with 10 mM sodium acetate, which gave 6.940 ± 0.057 g L⁻¹ biomass concentration, 327.619 ± 2.020 mg L⁻¹ day⁻¹ biomass productivity, 2.795 ± 0.191 g L⁻¹ lipid concentration, 131.955 ± 9.275 mg L⁻¹ day⁻¹ lipid productivity, and 40.286 % ± 3.079 % w/w LC. The optimum condition (10 mM sodium acetate) in an open pond cultivation attained maximum values at Day 14, that is, 0.575 ± 0.004 g L⁻¹ biomass concentration, 38.161 ± 0.076 mg L⁻¹ day⁻¹ biomass productivity, 0.203 ± 0.002 g L⁻¹ lipid concentration, 13.440 ± 0.197 mg L⁻¹ day⁻¹ lipid productivity, and 35.219 % ± 0.585 % w/w LC. The lipids recovered from mixotrophic micro-algae were primarily unsaturated fatty acids, which are appropriate to produce biodiesel. The results revealed that a 10 mM sodium acetate concentration can enhance lipid accumulation within algal cells.