Abstract: Four strains of Chlorella pyrenoidosa and 2 strains of Chlorella ellipsoidea under heterotrophic culture were analyzed for nutritional components and amino acid composition. Cluster analysis and principle component analysis were conducted to distinguish the differences among the heterotrophic strains of Chlorella sp.. The results showed that the contents of main nutritional components of the heterotrophic strains of Chlorella sp. were lower than previously reported results for autotrophic Chlorella sp.. The ratios of essential to total amino acids of the strains of Chlorella pyrenoidosa and Chlorella ellipsoidea were 34.94%－37.45% and 37.70%－38.32%, and the essential amino acid indexes 37.50－49.52 and 131.89－135.77, respectively. The limiting amino acids affecting the nutritional quality of 4 strains of Chlorella pyrenoidosa were Trp, Thr and Ile. The results of cluster analysis indicated that 4 strains of Chlorella pyrenoidosa and 2 strains of Chlorella ellipsoidea could be assigned to two different clusters according to the contents of nutritional components and amino acids. Two principal components were extracted to reveal a contribution rate of 76.23% for the first principle component and 17.80% for the second principle component. The cumulative contribution rate of the principal components was up to 94.03%.

Key words: heterotrophic Chlorella sp, nutritional components, amino acid, cluster analysis, principal component analysis