Boosting Arthrospira platensis metabolism during biogas upgrading via carbon coated iron-based nanoparticle addition

Carbon-coated iron-based nanoparticles have demonstrated a significant potential to enhance the performance of biological processes, particularly microalgal cultivation. In this study, the effect of two types of commercially available iron-based nanoparticles, namely CALPECH and SMALLOPS, was evaluated on Arthrospira platensis metabolism during biogas upgrading in batch cultures. Both nanoparticles enhanced CO 2 capture, O 2 production, cyanobacterial growth and phycocyanin synthesis across all tested concentrations. However, the highest phycocyanin content (180 mg·g -1 ) was reached by the addition of CALPECH nanoparticles at 100 mg·L -1 . Further experiments under stress conditions, including increased light intensity (300 and 600 μmol·m -2 ·s -1 ) and salinity (0.1-0.5 M NaCl) confirmed the beneficial effects of CALPECH. At 600 μmol·m -2 ·s -1 CALPECH nanoparticles enhanced biomass productivity and increased CO 2 capture by 33% while maintaining phycocyanin content at 178 mg·g -1 . Moreover, the addition of 100 mg·L -1 of CALPECH nanoparticles at 0.1 M NaCl slightly improved biogas upgrading performance and increased phycocyanin content to 192.7 mg·g -1 . In this context, increasing salinity to 0.5 M caused stress in Arthrospira platensis cells, reducing photosynthetic efficiency regardless of nanoparticle addition. These outcomes highlight the potential of carbon-coated iron-based nanoparticles to improve Arthrospira platensis growth and pigment production, which would ultimately increase the techno-economic feasibility of photosynthetic biogas upgrading. • Nanoparticle supplementation improved A. platensis growth and phycocyanin content. • CALPECH nanoparticles at 100 mg·L -1 improved phycocyanin content by 59%. • CALPECH nanoparticles lessened A. platensis photoinhibition at 600 μmol·m -2 ·s -1 . • Nanoparticle addition and 0.1 M NaCl enhanced phycocyanin content to 192.7 mg·g -1 .