Algal proteins may play both structural and nutritional roles, so their extraction from spent biomass is of potentially commercial interest. One application is for animal feed due their richness in essential amino acids (Williams and Laurens, 2010). The nonprotein nitrogen consists of amino acids, peptides, amines, and nucleotides and accounts for 10-20% of the total nitrogen in algae (Arasaki and Arasaki, 1983).

Recently, a few studies have been reported with respect to the organic solvent extractions due to the experience of remaining toxic residues with the target compounds, so enzyme — assisted extractions have attracted particular interest. Mechanical techniques such as ultra­sound sonication and pulverizing the lyophilized materials by grinding might also be helpful. Namely, bioactive peptides can be obtained in three ways: (1) hydrolysis by digestive enzymes from animals; (2) hydrolysis by proteolytic enzymes, harvested by microorganisms or plants; and (3) hydrolysis by proteolytic microorganisms during fermentation (Samarakoon and Jeon, 2012).