Heterotrophic cultivation of Euglena gracilis Z for efficient production of α-tocopherol |
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Authors: | James C Ogbonna Shota Tomiyamal Hideo Tanaka |
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Institution: | (1) Institute of Applied Biochemistry, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305, Japan;(2) CREST, Japan Science and Technology Corporation (JST), Japan |
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Abstract: | Effects of hydrodynamic stress, dissolved oxygen (DO) concentration and carbon sources on heterotrophic α-tocopherol production
by Euglena gracilis were investigated. In a jar fermentor without baffle plates, increasing the agitation speed up to 500
rpm had no significant effect on cell growth and α-tocopherol production. However, in a jar fermentor equipped with baffle
plates, both the cell growth and α-tocopherol production were highly suppressed at 500 rpm. At high hydrodynamic stress, the
cells secreted nucleic acid-related substances to the culture broth and the shape of the cells shifted from elongated toward
spherical. High DO concentration had adverse effects on both cell growth and α-tocopherol production, the optimum DO concentration
being below 0.8 ppm. In comparison with glucose, the growth rate was lower but the α-tocopherol content of the cells was almost
four times higher when ethanol was used as the organic carbon source. In a fed-batch culture with ethanol, a very high cell
concentration of 39.5 g L-1 was obtained with α-tocopherol content of 1200 μg g-cell-1. This α-tocopherol content is very close to the values reported for photoautotrophic and photoheterotrophic cultures. A very
high α-tocopherol productivity of 102 μg L-1 h-1 was obtained, indicating that heterotrophic cultivation of E. gracilis has a very high potential as a substitute for the
current method of extraction from vegetable oils.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | α -tocopherol heterotrophic culture Euglenagracilis hydrodynamic stress dissolved oxygen concentration |
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