Nutritional, Bio-Functional, and Antioxidant Properties of Enzymatic Hydrolysates Derived from Spirulina platensis Proteins

Spirulina (Arthrospira platensis) is recognized as a high-protein microalga with potential for bioactive peptide production. In this study, S. platensis protein extract (~45% protein) was subjected to enzymatic hydrolysis using pepsin, trypsin, and chymotrypsin. A ~75% reduction in Bradford values indicated extensive protein breakdown, with degrees of hydrolysis of 15.6%, 21.4%, and 33.7% for pepsin-, trypsin-, and chymotrypsin-treated samples, respectively. SDS-PAGE confirmed the generation of low-molecular-weight peptides (<10 kDa). Hydrolysis caused only minor changes in amino acid composition, maintaining protein quality, with trypsin-hydrolysates showing the highest protein efficiency ratio (1.12) and biological value (78.83%). Antioxidant capacity increased significantly, with hydrolysates displaying a 33–68% rise in DPPH and 30–54% in FRAP activity, alongside a 33–44% reduction in lipid peroxidation. Furthermore, phytochemical content was markedly enhanced in hydrolysates compared to intact protein, with increases in total phenolic content (38–118%), total flavonoid content (59–78%), and terpenoids (24–37%). Among treatments, trypsin-SPPH (Spirulina platensis protein hydrolysate) consistently exhibited the most pronounced improvements. Collectively, these findings demonstrate that proteolysis of S. platensis proteins not only enhances antioxidant activity but also liberates bound phytochemicals, establishing S. platensis hydrolysates as promising functional food and nutraceutical ingredients.