Application of statistically-based experimental designs for the optimization of eicosapentaenoic acid production by the diatom Nitzschia laevis

Statistically based experimental designs were applied to the optimization o f medium components and environmental factors for eicosapentaenoic acid (EP A production by the diatom Nitzschia laevis in heterotrophic conditions. Fi rst, the Plackett-Burman design was used to evaluate the effects of variabl es including medium components and environmental factors on cell growth and EPA production. Among these variables, NaCl, CaCl2, PI metal solution, pH, and temperature were identified to have the significant effects (with conf idence level > 90 %). Subsequently, the concentrations of NaCl, CaCl2, Pl m etal solution as well as the values of pH and temperature were optimized us ing central composite design. The cell growth and EPA production were found to respectively correlate to NaCl, CaCl2, pH, and temperature that could b e represented by second-order polynomial models. The optimal values of the four parameters were determined by response surface and numerical analyses as 8 g/L NaCl, 0.10 g/L CaCl2, pH 8.5 and 19.8 degreesC for cell dry weight (DW), and 14 g/L NaCl, 0.10 g/L CaCl2, pH 8.5 and 18 degreesC for EPA prod uction, respectively. The subsequent verification experiments confirmed the validity of the models. This optimization strategy led to a DW of 9 g/L, a n EPA yield of 280 mg/L and an EPA productivity of 28 mg/L/d, respectively, which were considerably higher than those obtained in the previous studies . (C) 2001 John Wiley & Sons, Inc.