Phycocyanin from Arthrospira platensis M2: mixotrophic production, extraction, partial purification, and investigation of some biochemical properties

In this study, to optimize the production conditions for obtaining maximum phycocyanin (PC) from Arthrospira platensis-M2, carbon (crude/technical glycerol) sources were examined in mixotrophic cultivation. The best production of PC was determined on the 15th day in mixotrophic cultivation (1 mM crude glycerol) as 3.75 ± 0.12 mg/g. The levels of bioactive components like total-protein, -carbohydrate, -lipid, and -carotenoid, chlorophyll-a, b, total-phenolic, -flavonoid and -tannin, lipid peroxidation, pyruvate, and proline were also investigated under optimal conditions. Then wet, lyophilized, oven-dried, and frozen samples were mixed with ultrapure water/buffer at four-different concentrations and mixer mill, freeze–thaw, homogenization, and ultrasound-assisted extraction (UAE) were applied to optimize PC extraction. PC extraction conditions were determined as 30 min at 80 kHz in the simple and environmentally/friendly UAE of a 5% ultrapure water-sample. Subsequently, ammonium sulphate (AS), organic solvent, and polyethylene glycol precipitation methods were applied. The best result was determined as AS precipitation at 50% saturation. After the sample was applied to DEAE-Sepharose column chromatography, the best fractions collected were combined and passed through the ultrafiltrate. Thus, PC with 2.30-reagent purity was obtained. Then, antioxidant (DPPH·, HO·, NO·, ABTS^·+, O₂^·−, metal chelating, total reducing power, and FRAP) and cytotoxic (OE-33 and HeLa cancer cells) properties of PC were detected. Additionally, UV–Vis spectrum, FT-IR, and TGA characterizations of PC were performed. To the results, it appears that partially purified PC, with its economical production in the presence of crude glycerol, can be considered a value-added bioactive product with potential for use in various industrial fields.