earticle

영어

Chlorella sp. was grown to produce biodiesel under mixotrophic condition in a recycling culture system (3 ℓ working volume) at 0.03 (ℓ/day) of recycling rate for 90days. Optimal culture conditions of mixotrophic growth were decided to be 25-30℃, 180 rpm and 3%(v/v) of CO2 supply. The effect of acetate as an organic carbon source was observed by adding various acetate concentrations: 5, 10, 15, 20 (g/L), respectively, and methanol, 0%, 0.05%, 0.1%, 0.5%, 1.0% and 3.0% (v/v), respectively. 10 (g/L) of acetate showed the maximum cell concentration as 4.8 (g-dry wt./L) with 19.8 (%, w/w) of total lipid production. While, at 5 (g/L) of acetate concentration, after 50 days the cell concentration showed relatively constant values as 2.9 (g-dry wt./L) of cell concentration. The optimal concentration of methanol was also determined as 1.0% (v/v), maintaining 4.2 (g-dry wt./L) of maximum cell concentration and 17.5% (w/w) of the total lipid production.
Particularly, there was almost no cell growth and total lipid production in adding 3.0% (v/v) of methanol because of highly toxicity. In observing residual concentrations of 10 (g/L) of acetate or 1.0(% (v/v)) of methanol, it was shown that the organic carbon source consumption rate was fast during the first period of cultivation and CO2 consumption rate was increased more during the last period of cultivation. This study confirmed that optimal concentrations of acetate or methanol as an organic substrate would be a important factor to maintain high the cell concentration and total lipid production.