Growth temperatures and various concentrations of ricinoleic acid affect fatty acid composition in two strains of...

The fatty acid composition of two strains (wild-type and M2 mutant cells of Hansenula polymorpha strain CBS 1976) were studied at different growth temperatures and various concentrations of ricinoleic acid. Two strains of yeast cultured on YEPD medium containing 1, 2, 3 and 8 mM of ricinoleic acid at 25, 30, 37 and 45 degrees C. Lipids were extracted from the yeast culture and the fatty acids esterified with BF3-MeOH. Gas chromatography analysis of total lipids showed that C16:1 (delta7), which has been synthesized in low concentration by WT strain, was found to increase in the M2 mutant. The biotransformation of C16:1 (delta7) found in M2 indicated the presence of dehydroxylation and beta-oxidation systems. An increase in the growth temperature from 25 to 45 degrees C resulted in a decrease in the total unsaturated fatty acids of C16:1, C18:1, C18:2 and C18:3 from 44.0 to 22.1% and 65.0 to 49.3% of the total fatty acids in M2 and wild-type strains, respectively. The differential production of unsaturated fatty acids, especially C16:1, indicated that regulation of unsaturated fatty acid levels, is an important control point in membrane composition in the adaptation of H. polymorpha M2 to diet and temperature.