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 [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.
Highlights
The role of Euglena gracilis as a good source of nutritionally and medically important substances has called for more research on how to maximize its production
Mixed substrate culture has been recognized as a technique for yield improvement in microbial cultivations
The growth of E. gracilis was found to be enhanced by the mixed substrate system relative to either of the single substrate cultures
Summary
The role of Euglena gracilis as a good source of nutritionally and medically important substances has called for more research on how to maximize its production. The main importance of E. gracilis is that it contains high amounts of proteins, vitamins and polyunsaturated fatty acids (PUFAs). It is used as health food and animal feed. Antioxidant vitamins such as α-tocopherol, L-ascorbic acid and β-carotene, which function to prevent diseases caused by oxidative damages among other functions, are accumulated in significant amounts by E. gracilis (Takeyama et al, 1997). E. gracilis is among the many photosynthetic microorganisms employed for production of single cell protein (SCP), a new food source, used as an alternative source of proteins in developed countries like Europe, America and Asia. We expected that the high growth of the cells observed in glucose and high α-tocopherol content in ethanol would be integrated in cells grown in a mixture of the two carbon sources
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