Abstract
The rising concentration of global atmospheric carbon dioxide (CO2) has severely affected our planet’s homeostasis. Efforts are being made worldwide to curb carbon dioxide emissions, but there is still no strategy or technology available to date that is widely accepted. Two basic strategies are employed for reducing CO2 emissions, viz. (i) a decrease in fossil fuel use, and increased use of renewable energy sources; and (ii) carbon sequestration by various biological, chemical, or physical methods. This review has explored microalgae’s role in carbon sequestration, the physiological apparatus, with special emphasis on the carbon concentration mechanism (CCM). A CCM is a specialized mechanism of microalgae. In this process, a sub-cellular organelle known as pyrenoid, containing a high concentration of Ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco), helps in the fixation of CO2. One type of carbon concentration mechanism in Chlamydomonas reinhardtii and the association of pyrenoid tubules with thylakoids membrane is represented through a typical graphical model. Various environmental factors influencing carbon sequestration in microalgae and associated techno-economic challenges are analyzed critically.
Highlights
Climate change is a major threat that severely hampers the survival of various plant and animal species as well as humans
Microalgae take up inorganic carbon in three different ways: (i) The transformation of bicarbonates into CO2 by extracellular carbonic anhydrase that readily diffuses inside the cells without any hindrance; (ii) straight absorption of CO2 via the plasma membrane; and (iii) direct intake of bicarbonates by resolute carriers in the membrane, known as dissolved inorganic carbon (DIC) pumps (Figure 1A) [44]
It has been determined throughout the study that microalgae have a higher CO2 tolerance, carbon assimilation efficiency, photosynthetic efficiency, and growth rate than terrestrial plants
Summary
Climate change is a major threat that severely hampers the survival of various plant and animal species as well as humans. The increased concentration of carbon dioxide around the thylakoid membrane enhances the efficiency of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), an important photosynthetic enzyme for carbon assimilation or sequestration. Rubisco has a low affinity for carbon dioxide as it has been evolved in high CO2 and low O2 environments, so the pyrenoid constantly provides an environment for enhanced CO2 fixation [18,19]. The review provides the current global CO2 emission status and scenarios
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