Nuclear mutagenesis and adaptive evolution improved photoautotrophic growth of Euglena gracilis with flue-gas CO2 fixation.

[Display omitted] • E. gracilis was modified with 60Co γ-ray and PEG adaptive to obtain strain M800. • Biomass and maximum CO 2 fixation rate of M800 were both 47% higher than wild strain. • Biomass of M800 with 1 mM PEG was 2.31 g/L, which was 79.1 % higher than wild strain. • M800 alleviate lipid peroxidation damage due to their higher antioxidant activities. • Cell proliferation of M800 was promoted, the apoptosis and necrosis rates decreased. To effectively improve biomass growth and flue-gas CO 2 fixation of microalgae, acid-tolerant Euglena gracilis was modified with cobalt-60 γ-ray irradiation and polyethylene glycol (PEG) adaptive screening to obtain the mutant strain M800. The biomass dry weight and maximum CO 2 fixation rate of M800 were both 1.47 times higher than that of wild strain, which was attributed to a substantial increase in key carbon fixation enzyme RuBisCO activity and photosynthetic pigment content. The high charge separation quantum efficiency in PSII reaction center, efficient light utilization and energy regulation that favors light conversion, were the underlying drivers of efficient photosynthetic carbon fixation in M800. M800 had stronger antioxidant capacity in sufficient high-carbon environment, alleviating lipid peroxidation damage. After adding 1 mM PEG, biomass dry weight of M800 reached 2.31 g/L, which was 79.1 % higher than that of wild strain. Cell proliferation of M800 was promoted, the apoptosis and necrosis rates decreased. [ABSTRACT FROM AUTHOR]