Abstract

Effects of media compositions on biomass and lipid accumulation of the isolate Chlorella sp. TISTR 8990 were investigated under a Plackett-Burman experimental design with mixotrophic cultivation conditions. Under this experimental design there were 15 different runs with ten factors-yeast extract, KH<inf>2</inf>PO<inf>4</inf>, MgSO<inf>4</inf>, FeSO<inf>4</inf>, MnCl<inf>2</inf>, CuSO<inf>4</inf>, Na<inf>2</inf>MoO<inf>4</inf>, H3BO<inf>3</inf>, ZnSO<inf>4</inf> and pH. Cultures were grown mixotrophically under 16 h light and 8 h dark regime at 30°C for a period of 7 days. During the light regime, the light intensity at the surface of the vessels and agitation speed were set to 67.5 μmol photons m^-2s^-1 and 150 rpm, respectively. Initial cell concentration was set to an absorbance (A<inf>540</inf>) of 0.5. For high biomass production (2.2 g/L, run no. 6), the most effective and significant factors were yeast extract, KH2PO<inf>4</inf>, FeSO<inf>4</inf> and ZnSO<inf>4</inf> at concentrations 0.3 g/L, 0.3 g/L, 3 mg/L and 0.3 mg/L, respectively. Whereas for high lipid accumulation (19.59 %DCW, run no. 2), these were KH2PO<inf>4</inf>, pH and yeast extract, at a level of 1.7 g/L, 6.0 and 0.1 g/L, respectively. No significant factors were obtained for higher lipid content. The best treatment for biomass and lipid content was run no. 6, whose medium formula consisted of 0.3 g/L yeast extract, 1.7 g/L KH<inf>2</inf>PO<inf>4</inf>, 1.7 g/L MgSO<inf>4</inf>, 1 mg/L FeSO<inf>4</inf>, 0.9 mg/L MnCl<inf>2</inf>, and pH 7.0, together with fixed concentrations of glucose, NaHCO<inf>3</inf> and KNO<inf>3</inf> at 5 g/L, 0.05 g/L and 0.5 g/L, respectively.