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

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 OD680nm = 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).