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Sustainable bioproduction requires improved carbon fixation in phototrophic microorganisms. Cyanobacteria such as Arthrospira platensis and Synechocystis sp. PCC 6803 convert CO 2 into biomass using sunlight, yet their growth under ambient conditions is often limited by low CO 2 solubility. Here, we report the development of self-assembling all-enzyme nanogels composed of carbonic anhydrase (CA) to enhance CO 2 bioavailability in cyanobacterial cultures. These carrier-free nanogels were formed through covalent self-assembly of CA variants fused to SpyTag or SpyCatcher domains and characterized using electrophoresis, dynamic light scattering, atomic force, environmental scanning electron, and confocal laser scanning microscopy. A custom pH-based CO 2 hydration assay showed that the nanogels retained high catalytic activity and stability for several weeks, and systematic analyses of buffer capacity revealed CA-dependent changes in the extracellular environment. Although CA supplementation had only minor effects on A. platensis , Synechocystis cultures exhibited a clear increase in biomass and chlorophyll content. Overall, CA nanogels represent a robust, carrier-free platform for enhancing CO 2 utilization and hold promise for applications in carbon capture, biomass production, and multi-enzyme cascade systems. • Carbonic anhydrase (CA) nanogels were synthesized through covalent self-assembly • Nanogels were characterized and their effect on culture pH and buffering assessed • Nanogels stayed active for weeks in cyanobacterial cultures • Nanogels boosted biomass and chlorophyll levels
Stoeckle et al. (Mon,) studied this question.