Comparative effects of autotrophic and heterotrophic growth on some vitamins, 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity, amino acids and protein profile of Chlorella vulgaris Beijerinck

Abstract

Chemical composition of Chlorella vulgaris Beijerinck including content of some vitamins (A, E and C), 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity, amino acids and protein profile was assessed under autotrophic and heterotrophic growth conditions as an indication of its nutritional value. Vitamin content (A, E and C) of heterotrophic cells increased by about 29, 52 and 20, respectively, as compared to its value for autotrophic cells. The free radical scavenging activity (RSA) was significantly higher for autotrophic cells than heterotrophic only at low concentrations (25 and 50 μl) of algal extract, but no significant difference was recorded at high concentration (100 μl). This result indicates non parallel relationship between the tested vitamins and RSA which suggest that other nonenzymatic antioxidants and/or antioxidant enzymes are involved. Concentration of essential and non essential amino acids in heterotrophic cells was double and 1.5 times, respectively its concentration in autotrophic cells. Histidine, lysine and phenylalanine constituted 77 and 44% of the total content of essential amino acids in heterotrophic and autotrophic cells, respectively. Methionine concentration was low in both types of cells. Proline content and non essential amino acid in heterotrophic cells was about 2.5 times its corresponding value in autotrophic cells. SDS-PAGE of protein extracts of autotrophic and heterotrophic C. vulgaris revealed two protein bands of molecular weight of ~75 and ~39 KDa. Higher intensity of the two bands was observed for autotrophic cells which may be associated with the effect of growth condition on the expression of regulatory genes. For valuable production of natural food supplement and/or natural pharmaceutical products, using heterotrophic cells rather than autotrophic cells for its richness in vitamins and essential amino acids is recommended.

Key words: Autotrophic, heterotrophic, Chlorella vulgaris, vitamins, 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity, amino acid, protein profile.