Enhancement of growth and gymnodimine production by the marine dinoflagellate, Karenia selliformis

Because of its novel bioactive properties the production of gymnodimine for use as a pharmaceutical precursor has aroused interest. The dinoflagellate, Karenia selliformis produces gymnodimine when grown in bulk culture using GP + selenium medium but the growth rates (μ) and levels of gymnodimine are low (μ, 0.05 days^?1; gymnodimine 250 μg L^?1 max). We describe the effects of organic acid additions (acetate, glycolate, alanine and glutamate additions and combinations of these) in enhancing growth and gymnodimine production in axenic cultures. The most effective organic acid combinations in decreasing order were: glycolate/alanine > acetate > glycolate. Glycolate/alanine optimised gymnodimine production by prolonging growth (maximum cell yield, 1.76 × 10⁵ cells mL^?1; gymnodimine, 1260 μg L^?1; growth rate (μ), 0.2 days^?1) compared to the control (growth maximum cell yield, 7.8 × 10⁴ cells mL^?1; gymnodimine, 780 μg L^?1; μ, 0.17 days^?1). Acetate enhanced gymnodimine by stimulating growth rate (μ, 0.23 days^?1) and the large concentration of gymnodimine per cell (16 pg cell^?1 cf. 9.8 pg cell^?1 for the control) suggests a role for this compound in gymnodimine biosynthesis. Amending culture media with Mn²⁺ additions resulted in slightly decreased growth in control cultures and increased the gymnodimine while in glycolate/alanine cultures growth was stimulated but gymnodimine production decreased. The results suggest that the organic acid can enhance gymnodimine production by either enhancing growth maximum or the biosynthetic pathway.