Aqueous two-phase based simultaneous extraction and purification of cephalopod melanin

The cephalopod processing industry generates large quantities of ink sacs, an underutilized yet valuable source of eumelanin. Conventional extraction of melanin, relying on acid or alkali treatments, often leaves residual proteins and carbohydrates, requires multiple purification steps, and risks pigment integrity. This study investigated a polymer-salt-based aqueous two-phase system (ATPS) as an eco-friendly alternative for the selective extraction and purification of melanin. Screening of polyethylene glycols of varying molecular weights with inorganic salts identified the PEG 6000-K₂HPO₄ system as the most effective. The equilibrium characteristic of the system was assessed using Othmer-Tobias and Bancroft correlations, while the partitioning behavior of melanin was evaluated by considering the process parameters, including polymer and salt concentrations, tie-line length, volume ratio, and sample loading. Under optimal conditions (tie-line length of 53.23% (w/w), a volume ratio of 0.14, and a sample loading of 15% (w/w)), melanin recovery reached 99.1% with 95% purity in the PEG-rich phase. These results outperform conventional methods in both yield and product quality, highlighting ATPS as a sustainable and scalable strategy for valorizing cephalopod waste, with promising applications in food, pharmaceutical, and biomedicine.