Plasma Mutagenesis of Haematococcus lacustris and Optimization of Culture Conditions for High-yield Astaxanthin Algae Strains

To further enhance the industrial utilization value of Haematococcus lacustris, the plasma mutagenesis of Haematococcus lacustris was carried out by an atmospheric and room temperature plasma (ARTP) mutagenesis equipment. The optimum input power and mutagenesis time for plasma mutagenesis were determined with lethal rate of algal cells as the index. After mutagenesis, high-yield astaxanthin mutant algae strains were obtained through primary screening of solid plate culture and secondary screening of liquid culture. Then, the culture conditions of high yield algal plants at vegetative growth stage were optimized by single-factor and orthogonal experiment with algae cell density as the index, and the suitable high light conditions for astaxanthin accumulation during astaxanthin induction stage were selected. The genetic stability of the high yielding mutant algae strains was observed after multiple subcultures under the optimized culture conditions. The results showed that the optimum conditions for plasma mutagenesis of Haematococcus lacustris were 240 W for 150 s or 400 W for 120 s. 11 Mutant alga strains with fast growth and high astaxanthin yield were obtained through primary screening and rescreening, wherein the strain HP3 grew fastest and had the highest astaxanthin yield. After culture, its cell density and astaxanthin yield were increased by 25.5% and 61.6% respectively compared with the original strain. After two-stage optimization, the cell density and astaxanthin yield of HP3 increased by 14.3% and 19.3% respectively, reaching 7.2×10⁵ cell/mL and 31.264 mg/L. HP3 showed good growth and stable heredity. Its cell density and astaxanthin yield were similar to those of primary culture. The results have practical significance for the breeding of industrial algal strains producing astaxanthin from Haematococcus lacustris.