Cell disruption and value-added substances extraction from Arthrospira platensis using subcritical water

As a ?green? solvent, subcritical water was applied to obtain valuable substances from Arthrospira platensis (A. platensis) in a semi-batch reactor at temperatures 180, 210, and 230 ?C with water residence time ranged from 12 to 17 s. Soluble protein and carbohydrates were major products. The maximum protein yields (55?60 wt %) were achieved at 180 ?C. The protein was found partially hydrolyzed to peptides and amino acids, which are potential emulsifier. The condition 210 ?C, 5 mL/min, was found optimal for carbohydrates extraction, and the extraction yield indicated that the structured carbohydrates were depolymerized and deaminated. The microscopy images of the solid residue clearly showed cells broken down. The C/N ratio of the aqueous extracts during extraction indicated that protein was released rapidly after cell disruption. An in-situ separation of protein from other extracted byproducts is proposed. The study demonstrates the feasibility of subcritical water extraction in the algal biorefinery.