Heterotrophic production of eicosapentaenoid acid by the diatom Nitzschia laevis:: effects of silicate and glucose

The effects of silicate and glucose on growth and eicosapentaenoic acid (EPA) production by the diatom Nitzschia laevis were studied. By alternately altering the concentrations of silicate (2.7-64 mg l(-1)) and glucose (1-40 g l(-1)) in the medium, the highest cell dry weight (ca. 5.5 g l(-1)) was obtained at 20 g l(-1) glucose and 32 mg l(-1) silicate, while the highest specific growth rate (ca. 0.65 day(-1)) was obtained at a relatively low glucose concentration (5 g l(-1)) and high silicate concentrations (32-64 mg l(-1)). At glucose levels of 5 and 20 g l(-1), EPA content was higher with lower silicate concentrations (2.7 and 16 mg l(-1) silicate, respectively), while at a silicate level of 16 mg l(-1), higher glucose concentrations (20-40 g l(-1)) facilitated EPA formation. The highest EPA yield (131 mg l(-1)) was obtained at 20 g l(-1) glucose and 32 mg l(-1) silicate, while the highest EPA productivity (15.1 mg l(-1) day(-1)) was obtained at 20 g l(-1) glucose and 64 mg l(-1) silicate.