The catalytic role of carbonic anhydrase in optimizing carbon fixation in microalgal cultures

Carbonic anhydrases (CAs) are metallo-enzymes that catalyze the hydration of carbon dioxide and are essential in physiological processes such as cellular growth, respiration, and pH homeostasis. In algae, CA facilitates photosynthesis, enabling efficient CO₂ assimilation. Microalgae, as photosynthetic microorganisms, offer significant potential for sustainable biomass production. However, large-scale cultivation is limited by the challenge of supplying CO₂. Atmospheric CO₂ diffuses too slowly to support rapid growth, and CO₂ sparging is both impractical and costly. An underexplored solution is the use of CA to enhance the direct capture of atmospheric CO₂, improving algae cultivation efficiency. While CA has been studied for CO₂ capture, its application in microalgae remains largely unexplored. This review provides a comprehensive understanding of CA, its diverse forms, and its roles in the carbon concentrating mechanism (CCM) of microalgae. The review focuses on CA's mechanism of action and its integration into algal cultivation systems, particularly its capacity to accelerate the dissolution of atmospheric CO₂. It also highlights the novel immobilization strategies for stabilizing CA at the air-water interface of algae cultivation systems. Positioning CA directly at the air-water interface significantly enhances CO₂ solubilization, leading to improved CO₂ uptake, more efficient carbon fixation, and the development of scalable, high-performance, and climate-resilient algae production systems.