Factors Affecting the Biomass and Lipid Production from Chlorella sp. TISTR 8990 under Mixotrophic Culture

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, KH₂PO₄, MgSO₄, FeSO₄, MnCl₂, CuSO₄, Na₂MoO₄, H₃BO₃, ZnSO₄ and pH. Cultures were grown mixotrophically under 16 h light and 8 h dark regime at 30 ºC 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 (A₅₄₀) of 0.5. For high biomass production (2.2 g/L, run no. 6), the most effective and significant factors were yeast extract, KH₂PO₄, FeSO₄ and ZnSO₄ 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 KH₂PO₄, 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 KH₂PO₄, 1.7 g/L MgSO₄, 1 mg/L FeSO₄, 0.9 mg/L MnCl₂, and pH 7.0, together with fixed concentrations of glucose, NaHCO₃ and KNO₃ at 5 g/L, 0.05 g/L and 0.5 g/L, respectively.