Microalgae of interest as food source: Biochemical composition and digestibility

Microalgae are considered a very interesting source for the development of new food products and can be used to enhance the nutritional value of conventional foods, due to their valuable biochemical composition. The aim of this study was to investigate the biochemical composition, the fatty acid profile and the in vitro digestibility of twelve microalgal biomasses (Arthrospira platensis F & M-C256; a bloom mainly composed of Aphanizomenon flos-aquae from Klamath Lake; Nostoc sphaeroides F & M-C117; Chlorella sorokiniana F & M-M49; Chlorella sorokiniana IAM C-212; Chlorella vulgaris Allma; Tetraselmis suecica F&M-M33, in nutrient replete medium and starved; Porphyridium purpureum F & M-M46; Phaeodactylum tricornutum F & M-M40; Tisochrysis lutea F & M-M36; Nannochloropsis oceanica F&M-M24) of interest as food source. The three cyanobacteria and the Chlorella species presented high protein (50-65%) and low lipid (5-20%) content. A high fiber content (14-17%) was found in T. suecica grown in nutrient replete medium, P. purpureum and P. tricornutum. Biomasses of marine species contained high concentrations of polyunsaturated fatty acids, mainly C20:5 omega 3 and C22:6 omega 3, along with substantial amounts of C16:1 omega 7, C18:1 omega 9 and C16:0. The freshwater algae contained high amounts of C18:3 omega 3 and an even higher amount of C16:0. A. platensis, C. sorokiniana IAM-C212 and C. vulgaris showed the highest digestibility, while T. suecica, P. tricornutum, and P. purpureum were the least digestible, likely because of the presence of robust cell walls or of exopolysaccharides that might have limited the action of digestive enzymes.