Occurrence of two nonmethylene-interrupted delta 5 polyunsaturated fatty acids in a delta 6-desaturase-defective mutant of the fungus Mortierella alpina 1S-4.

Two non-methylene-interrupted fatty acids, 5(Z),11(Z),14(Z)-eicosatrienoic acid (20:3 delta 5) and 5(Z),11(Z),14(Z),17(Z)-eicosatetraenoic acid (20: 4 delta 5), were found in a delta 6-desaturase-defective mutant of Mortierella alpina 1S-4. 20: 4 delta 5 was detected only when growth was at a temperature lower than 24 degrees C or in a culture medium supplemented with either alpha-linolenic acid or 11(Z),14(Z),17(Z)-eicosatrienoic acid. 20: 3 delta 5 was found when growth was at 12-28 degrees C. The amount of 20: 3 delta 5 was greatest (27 mg g-1 dry mycelia) when growth was at 20 degrees C, and it accounted for about 7 wt% of the total fatty acids of the mycelia. The optimum temperature for the accumulation of 20:4 delta 5 was 12 degrees C; there was 6.4 mg 20: 4 delta 5/g dry mycelia. Most of these two fatty acids (more than 75 mol%) was in the triacylglycerol fraction.