Effects of mixed substrates on growth and vitamin production by Euglena gracilis

Abstract

The effects of mixed carbon sources on growth and production of vitamins E and A by Euglena gracilis cells were investigated in batch culture. The cells were grown mixotrophically in glucose (G), ethanol
(E) and a mixture of glucose and ethanol (EG). Cell growth was measured by counting the cell number with microscope, while vitamin concentrations were measured spectrophotometrically. Growth of the
cells was found to be much better in the mixed carbon culture (EG) than in either glucose (G) or ethanol (E) alone. Significance difference was detected (P < 0.05) on cell growth and ranked as [EG] > [G] > [E].
The average cell density in the mixed carbon culture reached 2.34 ± 0.109 x 107 cells/ml after 7 days. It was about 1.63 ± 0.089 x 107 cells/ml in glucose and 0.70 ± 0.084 x 107 cells/ml in ethanol. The result also showed that ethanol alone was the best carbon source for production of the vitamins. The results indicated that the mixed carbon culture enhanced growth of the cells, but cellular contents of the
antioxidant vitamins were low. Thus, the mixed substrate system has a high potential for large-scale production of Euglena biomass.