Continuous cultivation of Arthrospira platensis using exhausted medium treated with granular activated carbon

Abstract

• Reusing Arthrospira platensis medium is important due to both its salinity and cost. • Granular activated carbon removes organic matter and pigments from the exhausted medium. • A. platensis continuous cultivation was carried out at different proportions of treated medium. • A. platensis growth was influenced by the different treated medium proportions. • Proteins content in dry biomass was high with up to 75% treated medium. Reusing culture medium of Arthrospira platensis is quite important in large scale production because its inappropriate disposal could exacerbate problems of environmental pollution. This study evaluates the suitability of using different quantities of exhausted Schlösser medium after continuous treatment using granular activated carbon (GAC) with a residence time ( T ) of 2 h for A. platensis growth in continuous cultivation. A tubular photobioreactor (PBR) and urea as cheap nitrogen source were used, taking as response variables kinetic parameters and biomass composition. The removal of both organic matter and pigment ( OMR and PgR , respectively) was measured to evaluate the efficiency of the treatment process. This treatment process yielded high values of OMR (73.7 ± 0.1%) and PgR (52.4 ± 0.4%) using 75% treated medium, thereby A. platensis biomass with high protein content (42.0 ± 0.6%), 1568 ± 15 mg/L cell concentration under steady-state conditions and 941 mg/L d cell productivity. This alternative to simultaneous treatment with GAC for reuse of Schlösser medium in continuous cultivation could ensure no diminution in either cell productivity or protein content in A. platensis cultivation using tubular PBR with 65% reduction in medium culture costs.