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

Abstract

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 CO2 capture, O2 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 nano- particles enhanced biomass productivity and increased CO2 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 nano- particles to improve Arthrospira platensis growth and pigment production, which would ultimately increase the techno-economic feasibility of photosynthetic biogas upgrading