Spirulina (Arthrospira platensis) immobilization in calcium-alginate beads can provide a way to produce food-grade C-phycocyanin following a biorefinery perspective

Abstract

C-phycocyanin (C-PC), a water-soluble blue pigment, is the primary phycobiliprotein in Spirulina. In this study, Spirulina was immobilized in calcium-alginate (SAC) beads as an innovative method to recover C-PC in the crosslinking bath while retaining the biomass within the beads. This approach simplifies the separation process and reduces costs. SAC beads were prepared via ionic gelation with alginate and CaCl₂ at 2 % (PC2) and 4 % (PC4) concentrations. Different Spirulina to CaCl₂ (S:CA) ratios (1:33, 1:42, 1:83, 1:125 w:v) were tested. PC4 extracts surpassed the food-grade purity threshold (≥ 0.7), achieving the highest purity of 0.83 at a 1:42 S:CA ratio. For PC2, the highest purity was 0.68, observed at a 1:83 S:CA ratio. Overall, this method effectively releases C-PC into the CaCl₂ bath, attaining food-grade purity with significant extraction yields (> 50 mg/g biomass). Additionally, the SAC beads exhibited high protein levels (> 25 g/100 g d.w.) and can be further utilized within a biorefinery framework, either directly as a food supplement or for cascade extractions to recover the remaining lipid and protein fractions.