HETEROTROPHIC CULTIVATION OF EUGLENA-GRACILIS Z FOR EFFICIENT PRODUCTION OF ALPHA-TOCOPHEROL

Effects of hydrodynamic stress, dissolved oxygen (DO) concentration an d carbon sources on heterotrophic alpha-tocopherol production by Eugle na gracilis were investigated. In ajar fermenter without baffle plates , increasing the agitation speed up to 500 rpm had no significant effe ct on cell growth and alpha-tocopherol production. However, in a jar f ermenter equipped with baffle plates, both the cell growth and alpha-t ocopherol production were highly suppressed at 500 rpm. At high hydrod ynamic stress, the cells secreted nucleic acid-related substances to t he culture broth and the shape of the cells shifted from elongated tow ard spherical. High DO concentration had adverse effects on both cell growth and alpha-tocopherol production, the optimum DO concentration b eing below 0.8 ppm. In comparison with glucose, the growth rate was lo wer but the alpha-tocopherol content of the cells was almost four time s 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 alpha-tocopherol content of 1200 mu g g-cell(-1). This alpha-tocopherol content is very close to the values reported fo r photoautotrophic and photoheterotrophic cultures. A very high alpha- tocopherol productivity of 102 mu g L-1 h(-1) was obtained, indicating that heterotrophic cultivation of E. gracilis has a very high potenti al as a substitute for the current method of extraction from vegetable oils.