[Continuous cultivation of Hansenula polymorpha and Candida krusei on mixtures of methyl and ethyl alcohols]

The object of this work was to study whether it would be possible to cultivate together ther the methanol-assimilating yeast Hansenula polymorpha M-2 requiring biotin and thiamine for its growth and the vitamin-prototrophic yeast Candida krusei E-10 actively growing in a medium with ethanol, without vitamin addition to the medium. The growth of the mixed culture in a medium containing ethanol and methanol depended on the pH of the medium; the biomass yield was maximal at pH 3.5 which was the suboptimal value for H. polymorpha M-2. The biomass yield decreased when the relative content of methanol in the mixed substrate was increased. At the optimal pH 3.5 and the optimal methanol-to-ethanol ratio (1:1), the productivity exceeded 2.0 g/litre per hour and the dilution rate D reached 0.17 h-1, the maximal value for H. polymorpha M-2 at this pH. The cultural broth obtained upon the growth of C. krusei E-10 on ethanol as a pure culture could not be used for the cultivation of H. polymorpha M-2 on methanol unless the vitamins were added.