Temperature and salinity effects on growth and fatty acid composition of a halophilic diatom, Amphora sp. MUR258 (Bacillariophyceae)

Abstract

Diatoms are of great interest for large-scale cultivation due to their high lipid content. The ability to grow over a wide range of salinities is also of great advantage. We studied the effect of temperature and salinity on the growth, lipids and fatty acid profiles of a newly isolated halophilic diatom Amphora sp. MUR 258. Amphora sp. MUR 258 is unusual in that it grows over a wide range of temperatures (24–35 °C) and salinities (7–12% (w/v) NaCl). The highest specific growth rate (SGR; 0.607 ± 0.017 day−1) was achieved at 7% NaCl at 35 °C, and the lowest SGR (0.433 ± 0.087 day−1) was obtained at 9% NaCl at 25 °C. The cells contained more lipids in the exponential phase, except when grown at 12% NaCl where the lipid content was higher in the stationary phase. The alga achieved its highest lipid content (57.69 ± 2.039% ash-free dry weight (AFDW) when grown at 7% NaCl at 25 °C and the lowest (34.43 ± 3.955% AFDW) obtained at 12% NaCl at 35 °C. The highest biomass productivity (0.171 ± 0.017 gAFDW L−1 day−1) and the lipid productivity (0.062 ± 0.017 gAFDW L−1 day−1) were achieved when the Amphora were grown at 9% NaCl at 35 °C and 7% at 25 °C, respectively. Irrespective of the growth conditions, the predominant fatty acids of Amphora sp. MUR 258 were palmitic acid (C16:0), stearic acid (C18:0), palmitoleic acid (C16:1) and oleic acid (C18:1), as well as low quantities of eicosapentaenoic acid (C20:5).