Intensified Phycobiliprotein Extraction from Spirulina Platensis by Freezing and Ultrasound Methods

In this study, the extraction of phycobiliprotein pigments from Spirulina Platensis dried powder was optimized using ultrasound-assisted extraction (ultrasonic water bath) combined with the freezing-thawing method. Response surface methodology (RSM) using Central Composite Designs (CCD) was employed to investigate the combined effect of two process variables of ultrasound time (30-90 min) and freezing-thawing time (5-12 h) on the amount of allophycocyanin (A-PC), C-phycocyanin (C-PC), phycoerythrin (PE), C-PC purity (EP), and the yield of C-PC. The purification of C-PC extracted from optimal and control conditions (extracted via freeze-thawing method without ultrasound) was performed, and the C-PC powder was evaluated by FT-IR spectroscopy and XRD. Results showed that at the optimal conditions of sonication time (55.5 min) and freezing time (5h), the average values of PE, A-PC, C-PC concentration, C-PC purity, and C-PC yield were (0.095±0.009), (0.051mg/g), (0.109±0.051mg/g), (0.498±0.25), and (2.32±0.21 %), respectively. The comparison of scanning electron microscopy images of algae biomass indicated that freezing alone and for a long time had caused more destruction of cells. The damage caused by ice crystals and large pores led to the production of extract with low purity. The ultrasonic pretreatment (5.5 min) for extracting the C-PC pigment from Spirulina Platensis compared to the control sample (12 h freezing without ultrasound) did not destroy the functional groups in the pigments.