Lipid Composition of a Thermotolerant Yeast,Hansenula polymorpha

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Abstract
A thermotolerant yeast, Hansenula polymorpha CK-1, which had an optimum growth temperature of 40°C, was isolated from bagasse. The fatty acid composition of the yeast grown at 40°C was characterized by the presence of oleic (18 :1, 25 to 27%), linoleic (18 :2, 42 to 43%) and linolenic (18 : 3, 3 to 6%) acids. An increase in the growth temperature from 20 to 50°C resulted in a decrease in the phospholipid content of cells from 2.84 to 1.24% on a dry weight basis, and reduced the proportion of 18 : 3 acid from 17.5 to 1.3% in phospholipids. The sterol content ranged between 0.34 and 0.53% of the dry weight of the cells. An increase in the molar ratio of sterol/phospholipid from 0.26 to 0.54 was observed with increasing temperature from 20 to 40°C, although no further increase in this molar ratio was found at 50°C. Since the decrease in fatty acid unsaturation in the phospholipids was not significant, the increase in the molar ratio of sterol/phospholipid may play an important role in the adaptation of H. polymorpha CK-1 to high temperatures.