Abstract
For assessment of the physiological significance of 9-methyl-4-trans,8-trans-sphingadienine (9-methyl base) in cerebroside-accumulating yeast, determination was made of the content and chemical compositions of cerebrosides in Kluyveromyces lactis and the results were compared for growth temperatures at 15°C, 25°C and 35°C. Compared with the culture prepared at the optimal growth temperature (25°C), greater time was required to reach the stationary phase of cells grown at 15°C. A reduction in cell weight was noted at 35°C. Cerebroside content in cells cultured at 15°C was significantly less than at 25°C or 35°C. Also, the ratio of cerebroside to phosphorus in the total lipid fraction at 15°C was less than at 25°C. In the 15°C culture, the 9-methyl base, the most predominant fungal cerebroside sphingoid base, increased beyond that in the 25°C preparation, though was essentially the same as at 35°C. K. lactis is thus shown to modulate not only the content but sphingoid base composition of cerebrosides in response to temperature. Fatty acid compositions in all cerebrosides examined were the same. These and the results from a previous study (J. Oleo Sci., Vol. 51, 741-747, 2002) provide basis for assuming 9-methyl branched chain in yeast cerebroside molecules to be essential for maintaining sufficient membrane fluidity for a low temperature environment.
