Chemical characterization and nutritional evaluation of microalgal biomass from large-scale production: a comparative study of five species

Biomass from five microalgal species, Porphyridium cruentum, Isochrysis galbana, Phaeodactylum tricornutum, Tetraselmis suecica and Nannochloropsis gaditana, produced at an industrial plant in outdoor photobioreactors, was studied with the aim to evaluate their suitability to the food and nutraceutical sectors. Microalgal biomass was analyzed for proximates, nonprotein nitrogen, energy, fatty acids, minerals, trace elements and mercury contents. Proximate analyses showed wide differences among microalgal species, in accordance with their different taxonomic position, especially as regards protein (19.6-33.2% dry mass), carbohydrate (15.9-42.2% dry mass) and lipid (5.7-31.1% dry mass) contents. All species proved to be a good source of minerals and trace elements and of polyunsaturated fatty acids (47.4-59.1% of total fatty acids) with varying profiles. N-3 fatty acids were prevalent in P. tricornutum, N. gaditana, I. galbana and T. suecica (32.6-36.4% of total fatty acids), whereas n-6 fatty acids, mainly arachidonic (C20:4) and linoleic (C18:2) acids, were prevalent in P. cruentum (43.3% of total fatty acids). N. gaditana, P. tricornutum, and P. cruentum were rich in eicosapentaenoic acid (36.0, 29.3%, and 15.9% of total fatty acids, respectively), while I. galbana was a good source of stearidonic (C18:4, 12.2% of total fatty acids) and docosahexaenoic (9.0% of total fatty acids) acids, undetectable or present at low levels in the other species. I galbana and T. suecica showed also high percentages of alpha-linolenic acid (C18:3, 12.2%-15.7% of total fatty acids). All microalgae were characterized by good nutrient contents and confirmed to be potentially valuable ingredients for nutritional or nutraceutical purposes.