Reduced chlorophyll antenna mutants of Chlorella saccharophila for higher photosynthetic efficiency and biomass productivity under high light intensities

The efficiency of light utilisation through photosynthesis is the most critical factor for microalgal growth. Microalgae face photo-damage at higher light irradiance due to over absorption of light energy. Photosynthesis becomes light-saturated with the increase in light intensity, primarily due to larger antenna size. The strain improvement with reduced antenna size is thus desirable for the optimum conversion of sunlight to algal biomass. The present work describes the generation of reduced chlorophyll antenna mutants of Chlorella saccharophila by EMS mutagenesis. A high light–acclimated mutant exhibited a 21% reduction in total chlorophyll fluorescence, 37% and 15% reduction in PSII and PSI antenna size respectively, with increased biomass productivity and non-photochemical quenching. All these improved photosynthetic parameters led to a 27% increase in biomass productivity under ≥ 1200 μmol photons m −2 s −1 light irradiance. The high light tolerance and biomass productivity establish the Chlorella saccharophila as promising algal species to be grown at large scale for biofuels.