Carbonic Anhydrase-Integrated Silk Hydrogels for Efficient Microalgae Growth and Carbon Fixation

Microalgae can capture CO₂ from the air and convert it into biomass and valuable byproducts, positioning these organisms as the key in terms of sustainable carbon fixation technologies. However, cultivating microalgae efficiently and cost-effectively remains a significant challenge. In this study, we enhanced the cultivation of microalgal cells within a silk/alginate hydrogel, shielded by CO₂ adsorption/desorption functional fabrics, to generate an innovative sandwich-structured composite system. Additionally, carbonic anhydrase-encapsulated silk fibroin nanoparticles were synthesized and co-embedded with the microalgae in the hydrogel. This silk-based microencapsulation sustained enzymatic activity, improving the conversion of CO₂ to bicarbonate and providing vital inorganic carbon for microalgal growth. The integration of microchannels within the gel facilitated continuous flow of culture medium via a microinjection pump, addressing nutrient deficiencies during prolonged exposure to air. Our findings indicate that microalgae cultivated in this system exhibit a significantly higher growth rate and carbon fixation rate compared to control setups, highlighting their potential as a carbon fixation system.