COMPARISON OF DIFFERENT EXTRACTIVE PROCEDURES FOR PROTEINS FROM THE EDIBLE SEAWEEDS ULVA-RIGIDA AND ULVA-ROTUNDATA

Proteins have been extracted from the edible seaweeds Ulva rigida Agar dh and Ulva rotundata Bliding using classical or enzymatic procedures. The protocols using NaOH under reductive conditions or a two-phase sy stem (PEG/K2CO3) produced the best protein yields. The cleavage or the limitation of the linkages between proteins and polysaccharides cause d by these experimental conditions probably explains the efficiency of these protocols. In SDS PAGE, the protein fraction obtained after NaO H extraction from U. rotundata is characterised by the presence of thr ee major bands with apparent molecular weights of 45 600, 31 800 and 1 8 600. The protein fraction from U. rigida presents two specific bands with apparent molecular weights of about 27 000 and 12 000. These fra ctions are mainly rich in aspartic and glutamic acids, alanine, glycin e and contain few hydroxyproline residues (0.91-2.44% total amino acid content). The use of cellulase does not significantly improve the ext raction of algal proteins in comparison with the blank procedure (with out enzymes). The weak accessibility of the substrates in the intact c ell wall could explain these experimental data. The improvement of pro tein yield after the use of the polysaccharidase mixture (beta-glucana se, hemicellulase, cellulase) partially confirms this hypothesis.