Repeated mutagenic effects of 60Co-γ irradiation coupled with high-throughput screening improves lipid accumulation in mutant strains of the microalgae Chlorella pyrenoidosa as a feedstock for bioenergy

In this study, the repeated mutagenic effects of 60Co-γ irradiation combined with an optimized high-throughput screening method was applied to Chlorella pyrenoidosa to improve lipid productivity and characteristics for biodiesel. Two mutants of Chlorella pyrenoidosa, CP-232 and CP-269, were obtained. The lipid contents obtained from CP-232 and CP-269 were respectively increased by 20.8% and 20% under heterotrophic seed-photoautotrophic culture (HS-PC) model, and by 15% and 20.8% under photoautotrophic seed-photoautotrophic culture (PS-PC) model compared with the wild type strain in 1 L bubble column reactor. In addition, 60Co-γ irradiation mutagenesis increased the proportion of saturated fatty acids in lipids accumulated in CP-232 and CP-269 compared to the wild type strain. In 3 L and 15 L bioreactor scale-up, lipid productivity was equally significantly increased in both CP-232 and CP-269 mutant strains. Our findings indicated that 60Co-γ irradiation mutagenesis improves the accumulation of lipids with potential for industrial biodiesel production in mutant C. pyrenoidosa strains.