Enhanced potential of a Selenastrum capricornutum mutant for CO2 fixation and biofuels production

There is an urgent need to screen candidates for CO2 fixation and biofuels production from more taxonomic species. A Selenastrum capricornutum mutant, whose wild types were not considered as candidates for CO2 fixation and biofuels production, with genetic stability under high-level CO2, here, was screened by 96-well microplates-UV mutagenesis and named as SDEC-2M. To evaluate the potential for CO2 fixation and biofuels production, SDEC-2M was cultivated under air and 15% CO2 (v/v), and its wild type (WT) as control. SDEC-2M got better growth performance under high-level CO2. It implies that SDEC-2M had high tolerance under high-level CO2. Under high-level CO2, not only that, SDEC-2M tended to synthesize energy storage compounds than its wild type, with a total carbohydrate content of up to 37.45%. Meanwhile, the highest overall biomass productivities were obtained in SDEC-2M under 15% CO2. Benefiting from these results, the highest productivities of carbohydrate, lipid and protein were obtained, among which carbohydrate productivity of 11.22 mg L-1 d(-1) was highest. Based on higher light conversion efficiency (14.81%) and maximal PSII quantum yields (70.14%), the highest photosynthetic efficiency of SDEC-2M was also evaluated under 15% CO2. Compared with Selenastrum wild types, the mutant SDEC-2M with excellent CO2 tolerance and photosynthetic efficiency is better. The results provided a new idea for further enriching the energy microalgal pool.