Gradient domestication of Haematococcus pluvialis mutant with 15% CO2 to promote biomass growth and astaxanthin yield

•15% CO2-tolerant Haematococcus pluvialis mutant was obtained with domestication.•The biomass yield with 15% CO2 increased by 30% than that with air.•The astaxanthin yield with 15% CO2 were 6 times higher than that with air. In order to increase biomass yield and reduce culture cost of Haematococcus pluvialis with flue gas from coal-fired power plants, a screened mutant by nuclear irradiation was gradually domesticated with 15% CO2 to promote biomass dry weight and astaxanthin yield. The biomass yield of mutant after 10 generations of 15% CO2 domestication increased to 1.3 times as that with air. With the optimization of nitrogen and phosphorus concentration, the biomass dry weight was further increased by 62%. The astaxanthin yield induced with 15% CO2 and high light of 135 μmol photons m−2 s−1 increased to 87.4mg/L, which was 6 times higher than that induced with high light in air.