A systematic analysis and evaluation of nutritional composition of 23 strains of marine microalgae commonly used in aquaculture

To better understand and compare the nutritional compositions of marine microalgae, 23 strains from four phyla (Haptophyta, Chlorophyta, Ochrophyta, and Bacillariophyta) belonging to eight classes were cultivated under same conditions and their proximate (protein, carbohydrate, and lipid), amino acid, fatty acid, vitamin, and pigment compositions were investigated. Moreover, the principal component analysis (PCA) and grey relational analysis (GRA) were performed to distinguish and evaluate their nutritional values. Results showed that the protein, carbohydrate, and lipid contents in those microalgae varied from 214.80 to 644.30 mg·g−1 dry weight (DW), 22.64 to 196.23 mg·g−1 DW, and 73.33 to 367.87 mg·g−1 DW, respectively. Arginine, tyrosine, and glutamic acid were the dominants in most species. All species could be distinguished by representative fatty acids, and were rich in 20:5n-3 or 22:6n-3 except for chlorophytes. Vitamin B2 and B3 were relatively high in most species examined while vitamin A and B6 were relatively low. Specifically, the chlorophytes were characterized by abundant vitamin C, while the prymnesiophytes and Auxenochlorella pyrenoidosa were characterized by abundant vitamin E. A total of 14 kinds of pigments were identified, and chlorophyll-a was abundant in green algae while carotenoids (especially fucoxanthin) were abundant in brown/golden algae. The PCA result showed that the nutritional characteristics of prymnesiophytes, pavlovophytes, and dictyochophyte were well distinguished from the other strains. The GRA result ranked Isochrysis galbana as the highest nutritional value (0.782) while Navicula pelliculosa as the lowest value (0.605). Collectively, the present study showed that the marine microalgae derived from different phyla or even the same class had obviously different nutritional compositions, especially represented by fatty acids, vitamins, and pigments. These results would be greatly beneficial to the utilization of the nutrients of marine microalgae in aquaculture and other industries.