Mass cultivation of Dunaliella salina in a flat plate photobioreactor and its effective harvesting

Abstract

Mass cultivation of Dunaliella salina was standardized in a flat plate photobioreactor followed by a vertical flat plate photobioreactor. Maximum biomass productivity (14.95 ± 0.43 mgL^-1d^-1 dry cell weight) was achieved in the latter at inoculum concentration of OD_680nm = 0.1, 100 µmolm^-2s^-1 light illumination and 1.0 L min^-1 aeration. Semicontinuous operation with varying KNO₃ and NaHCO₃ concentrations resulted highest biomass productivity (17.85 ± 0.55 mgL^-1d^-1) at 0.50 mM NaHCO₃ and 15 mM KNO₃. However, maximum lipid (16.36 ± 1.18% dry cell weight) was achieved at 0.75 mM NaHCO₃ and 10 mM KNO₃. Flocculation studies employing potash alum, FeCl₃·6H₂O or pH showed harvesting efficiencies exceeding 90% in 0.75 mM potash alum or FeCl₃·6H₂O or pH 11, but they yielded low concentration factor (<5) and were detrimental (Fv/Fm < 0.50). A combination of 0.50 mM FeCl₃·6H₂O and pH 9 was found as most suitable flocculating strategy with maximum concentration factor (>14) and least damaging (Fv/Fm > 0.54).

Keywords: Dunaliella salina; Flocculation; Photobioreactor.