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.