optimization of Lipid Accumulation by Starchless Mutant Chlorella sorokiniana for Biodiesel Production

Abstract

Improvement of oil accumulation in Chlorella sorokiniana was conducted by ultraviolet mutagenesis. In total, 63 starchless mutants from over 40,000 colonies were screened using an iodine fumigation technique. Eight starchless mutants had relatively high levels of oil accumulation compared to wild type strains. The lipid content of starchless C. sorokiniana DMKU5202-31 increased from 15% to 21.16%. Therefore, this strain was selected for further optimization using a statistical experimental design. Seven factors were screened using a Plackett-Burman design and further optimized using a central composite design (CCD). The Plackett-Burman design presented three significant factors—KNO3, pH and light intensity—that affected biomass and lipid accumulation significantly. CCD was used to optimize the significant factors and indicated that the optimal values for KNO3, pH and light intensity were 0.9 g.L-1, 6.2 and 4,000 lux, respectively. The response surface plots revealed that the maxima for biomass, lipid production and lipid content were 2.58 g.L-1, 1.40 g.L-1 and 54.49%, respectively. Thus, it could be concluded that ultraviolet mutation and the statistical experimental design can be used to improve oil accumulation in C. sorokiniana. After mutation and optimization, strain DMKU5202 had a lipid content increase from 15% to 54.49%. Therefore, these techniques were very efficient for the development of an upstream process for biodiesel production.