Enzyme-assisted extraction and characterization of protein from red seaweed Palmaria palmata

This investigation aimed at protein extraction from red seaweed Palmaria palmata, by application of an optimized enzyme-assisted extraction consisting of an aqueous/enzymatic treatment followed by alkaline extraction. Accordingly, the protein extraction efficiency of four enzymes was evaluated including Celluclast® 1.5 L, Shearzyme® 500 L, Alcalase® 2.4 L FG and Viscozyme® L at 0.0, 0.2 and 0.4% (w/w), at different pHs and temperatures. The protein content of the raw material and the fractions from the extraction were analyzed by using the Dumas method and multiplying with the nitrogen to protein factor 5.0. The results showed that the enzyme combinations containing Alcalase® and either Celluclast® or Shearzyme® achieved the highest (>90%) protein extraction efficiencies (p < .05). The amino acid content and composition in the raw material and in the fractions obtained from the treatment using each enzyme individually and also with the combination of Alcalase® plus Celluclast® as an optimum extraction were determined by LC-MS. The results showed that the total amount of essential amino acids (EAA) were higher in the solid fractions (post extraction solid residue and pellet) after all enzymatic treatments compared with the raw material (untreated seaweed). The EAA accounted for approximately 50% of total amino acids (AA) found in the solid samples with the EAA/AA ratio ranging from 0.47 to 0.55. In comparison, in the liquid fraction, the EAA/AA ratio varied from 0.2 to 0.44. The maximum EAA/AA ratio was found when Alcalase® alone were employed (0.44).