Recent advances in CO₂ uptake and fixation mechanism of cyanobacteria and microalgae

ABSTRACT

Aquatic photosynthetic microorganisms, cyanobacteria and microalgae, account for almost half of the world's photosynthesis. They absorb carbon di oxide (CO₂) as the major substrate to support photosynthesis, the beginning of energy flow into living organisms and one of the primary processes comprising the global carbon cycle. Among all photosynthetic mechanisms, inorganic carbon transport into ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) is one of the major limiting steps in photosynthetic carbon fixation which involves active transport of HCO₃⁻, CO₂ and/or H⁺, or an energized biochemical mechanism. In fact, a unique system “carbon concentrating mechanism (CCM)” manages the inorganic carbon assimilation, accumulation of CO₂ around RuBisCO, and utilization in algal cells. However, the information on mechanism of CO₂ uptake and fixation inside the algal cells is limited. In order to make strategies for enhancement of CO₂ fixation, understanding of CCM is crucial. Thus, this review provides an overview of advances in CCM research, the comparative state of the art and reports on the CO₂ uptake model in cyanobacteria and microalgae. The review also discusses the challenges and future perspectives associated with algal CCM research.

KEYWORDS:

• Carbon concentrating mechanism
• CO₂ uptake and fixation
• cyanobacteria
• microalgae

Funding

Authors are thankful to the Science & Engineering Research Board (SERB) and the Department of Science and Technology (DST), India, for their continued financial support and encouragement through the DST-Young Scientist grant for our research on CO₂ mitigation using cyanobacteria and microalgae.