In the present contribution, the differentiation in the molecular structure and function of the photosynthetic apparatus of the unicellular green alga Chlorella vulgaris was studied at several light intensities (0–400 μmol m−2 s−1) and various CO2 concentrations (0.04–60% CO2), in completely autotrophic conditions. Asymmetries that occur by different light intensities and CO2 concentrations induce metabolic and functional changes. Using chlorophyll fluorescence induction techniques (OJIP test), we showed that Chlorella vulgaris tolerates extremely high CO2 levels and converts them photosynthetically into valuable products, including O2 and biomass rich in carbohydrates and lipids. Interestingly, the microalga Chlorella vulgaris under extremely high CO2 concentrations induces a new metabolic state intensifying its photosynthetic activity. This leads to a new functional symmetry. The results highlight a potent CO2 bio-fixation mechanism of Chlorella vulgaris that captures up to 288 L CO2 L PCV−1 day−1 under optimal conditions, therefore, this microalga can be used for direct biological CO2-reducing strategies and other green biotechnological applications. All of the above suggest that Chlorella vulgaris is one of the most prominent competitors for a closed algae-powered bioreactor that is able to consume huge amounts of CO2. Thus, it is a sustainable and natural bioenergetic system with perspectives in dealing with major environmental issues such as global warming. In addition, Chlorella vulgaris cultures could also be used as bioregeneration systems in extraterrestrial missions for continuous atmospheric recycling of the human settlements, paving the way for astrobiological applications.
Regulation of Energy Balance in Photosystems in Response to Changes in CO2 Concentrations and Light Intensities during Growth in Extremely-High-CO2-Tolerant Green Microalgae
