EMS-induced mutation followed by quizalofop-screening increased lipid productivity in Chlorella sp.

The objective of this study was to enhance biomass and lipid productivity in Chlorella sp. isolate 6-4 by inducing mutagenesis with two growth inhibitors: the herbicide quizalofop-P-ethyl, a known inhibitor of acetyl-CoA carboxylase (ACCase) activity, and chemical mutagen, ethyl methanesulfonate (EMS), at different concentrations and length of times. The induced-mutagenized microalgae were screened on selective medium containing 10-100 µM quizalofop. The biomass yield, biomass productivity, lipid content, and lipid productivity of mutagenized microalgae were determined. The result showed that 100-200 mM EMS concentrations and 30 min incubation time were the most effective. Biomass yield and biomass productivity of the mutagenized microalgae E50-30-40, E100-60-40, and E100-30-60 were statistically significant higher than those of the wild type. The mutagenized microalgae E100-30-60 showed that the highest biomass yield and biomass productivity were 111 and 110% higher than the wild type, respectively (p < 0.01). Lipid content and lipid productivity of the mutagenized microalgae E200-30-40 were 59 and 53% significantly higher than the wild type, respectively. It should be noted that biomass productivity of the mutagenized microalgae E200-30-40 was not significantly different from E100-30-60, meaning that this microalga strain exhibited highest both biomass and lipid productivity. These results indicated that inducing mutagenesis by EMS subsequently screening by herbicide could lead to enhance biomass and lipid accumulation. Therefore, this methodology could be used for improvement microalgae for biofuel production.