Chiang Mai Journal of Science

 Chlorella sp. is a green microalga and well-known for its ability to accumulate high amount of lipid in the cells. This alga was considered to be a potential energy source for biodiesel production. The objectives of this study were to re-mutate the Chlorella sorokiniana DMKU5202-31 which was the UV mutant strain by using Ethyl methanesulfonate (EMS), a chemical mutagen and optimization of culture condition of the double mutant strain for oil production. After treatment with 0.5 M EMS for 1 h 40,323 colonies was obtained and subjected to screening. The double mutant strain C. sorokiniana DMKU5202-D223 was selected due to its high lipid production. For optimization of culture condition, the Central Composite Design (CCD) and Response surface methodology (RSM) were employed. The experiment model concluded that glucose concentration of 10 g/L, pH 8, 3% CO₂ and light intensity 3,000 lux were suitable to enhance oil production. The optimization of oil production conditions of C. sorokiniana DMKU5202-D223 showed from the RSM and CCD as followed: 6.32 g/L of biomass production, 0.65 g/L of lipid production, and 10.45% of lipid content within 5 days. Comparison of oil production by the double mutant strain under these optimum conditions to the UV mutant strain and the wild type strain revealed that the double mutant strain had oil production higher than UV mutant strain and wild type strain. The UV mutant strain and wild type strain had lipid production 0.54 g/L and 0.22 g/L while lipid content were 8.38% and 4.96%. In conclusion, the double mutant strain showed relatively high oil production and could be used as the raw material for biodiesel production.