Abstract
High-value products from microalgae, which can be used in various applications (nutritional, pharmaceuticals and cosmetic) can considerably increase the commercial value of microalgal biomass. This research focuses on the following: - Green extraction of proteins from the marine diatom Nitzschia laevis (N. laevis) and comparing them with those obtained from well-studied species such as Spirulina (Arthrospira) platensis (S. platensis) and Chlorella vulgaris (C.vulgaris). - Protein extracts obtained were subjected to three different protease enzymes including Trypsin, AlcalaseCLEA and Flavourzyme to produce bioactive hydrolysates. - Screening of anti-oxidative, anti-hypertension, anti-inflammatory and antimicrobial activities in vitro. - Fractionation and characterization of bioactive proteins and hydrolysates produced from the microalgal extracts using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Soluble proteins and other major constituents (lipids and carbohydrates) from N. laevis were extracted using ultrasound, then compared to other well-investigated microalgae (Spirulina and Chlorella). Protein extracts and hydrolysates did not show antibacterial or bactericidal activities against the tested organisms with the used range of concentrations. Aqueous protein extracts and hydrolysates from Nitzschia, Spirulina and Chlorella have shown in vitro antioxidant, anti-angiotensin I-converting enzyme and anti-acetylcholinesterase activities, suggesting potential new sources of bioactive proteins and peptides of different phyla with nutraceutical and pharmaceutical potentials. Until now, most of the biological activities of microalgal-derived bioactive proteins and hydrolysates have been observed in vitro. Therefore, further ex vivo research studies are needed in order to investigate their potential market as nutraceuticals and pharmaceuticals based on their therapeutic potential shown in this study.