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 (EP A) production by the diatom Nitzschia laevis were studied. By alternately a ltering 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 o btained at 20 g l(-1) glucose and 32 mg l(-1) silicate, while the highest s pecific growth rate (ca. 0.65 day(-1)) was obtained at a relatively low glu cose 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 l ower 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 hi ghest EPA productivity (15.1 mg l(-1) day(-1)) was obtained at 20 g l(-1) g lucose and 64 mg l(-1) silicate.