Fatty-acid composition of Candida utilis as affected by growth temperature and dissolved-oxygen tension.

Abstract

Analyses were made of the fatty-acid composition of Candida utilis NCYC 321 grown in a chemostat at a dilution rate (equal to growth rate) of 0.1 hr(-1) and at temperatures in the range of 30 to 15 C and dissolved oxygen tensions between 75 and <1 mm of Hg. Cells grown under glucose limitation or NH(4) (+) limitation contained mainly C(16:0), C(16:1), C(18:0), C(18:1), C(18:2), and C(18:3) acids as detected by gas-liquid chromatography of methyl esters of the acids from lipids extracted with chloroform-methanol. The relative proportions of these acids varied with the growth temperature and the dissolved-oxygen tension in the culture. A decrease in growth temperature from 30 to 20 C led to an increased synthesis of unsaturated acids in cells grown under either limitation at a fixed-oxygen tension in the range of 75 to 5 mm of Hg. In cultures with a dissolved-oxygen tension of 1 and <1 mm of Hg, a further decrease in temperature to 15 C caused an increased synthesis of unsaturated fatty acids. A decrease in dissolved-oxygen tension led to a diminished synthesis of unsaturated fatty acids in cells grown at a fixed temperature under either limitation. Cells grown at a fixed temperature under glucose limitation synthesized a greater proportion of C(16) acids at the expense of C(18) acids as the dissolved oxygen tension was decreased from 75 to <1 mm of Hg. A preferential synthesis of C(16) acids also occurred as the growth temperature was decreased from 30 to 15 C in cells grown under glucose limitation at a fixed-oxygen tension. The same effect was observed in cells grown under NH(4) (+) limitation when the temperature was lowered from 30 to 20 C; but when the temperature was decreased further to 15 C, the cells synthesized a slightly greater proportion of C(18) acids. Synthesis of a large proportion of C(16) acids was accompanied by an excretion of pyruvate, and occasionally traces of 2-ketoglutarate, and an increased intracellular accumulation of certain amino acids.