Abstract:A Chlorella strain 2003ZGH023 was cultured at modes of photoautotrophic (light, basic nutrient formula), mixotrophic with high carbon level (light, basic nutrient formula, 8 gram organic carbon per liter), mixotrophic with low carbon level (4 gram organic carbon perliter), and heterotrophic with low carbon level (darkness, basic nutrient formula, 4 gram organic carbon per liter) respectively. The effects of different trophic modes on the growth performance and nutritional composition of the Chlorella were studied. The results indicated that the addition of organic carbon in culture medium significantly increased the cell density and biomass of the Chlorella. The heterotrophic group had a cell density as high as 54.73×106 cell/ml, and biomass of 6.86 g(dw)/L. The sizes of the Chlorella cells in heterotrophic and mixotrophic groups were larger than that in autotrophic group. The assays on nutrition showed that the protein content of the Chlorella cell declined significantly while the total fat content increased significantly in the heterotrophic modes. The crude protein contents in the photoautotrophic mode, mixotrophic mode with high carbon level, mixotrophic mode with low carbon level and heterotrophic mode were 41.88%±0.14%, 24.60%±0.07%, 21.93%±0.13% and 12.91%±0.35% respectively. The variation of amino acid content in cell at different trophic modes was consistent with that of crude protein. The total lipids in the mixotrophic mode with high carbon group (15.32%±1.58%) and the heterotrophic mode with low-carbon group (14.15% ± 0.93%) were significantly higher than those in the mixotrophic mode with low-carbon group (12.35% ± 0.25%) and the photoautotrophic mode (10.04% ± 0.3%). There were significant differences in fatty acid compositions of cell cultured in different trophic modes. Fatty acids 18∶3n3 and 14∶1 were dominant in photoautotrophic Chlorella. Fatty acids 14∶1 and 18∶1n9 were the majority in the mixotrophic modes. Fatty acids 18:1n9 and 16:0 were the most abundant in the heterotrophic mode.
