Production of 5,8,11‐<i>cis</i>‐eicosatrienoic acid by a Δ12‐desaturase‐defective mutant of<i>Mortierella alpina</i> 1S‐4

Abstract

A mutant defective in Δ12‐desaturase of an arachidonic‐acid producing fungus, Mortierella alpina 1S‐4, was shown to be a novel potent producer of Mead acid (5,8,11‐ cis ‐eicosatrienoic acid, 20:3ω9). The fungus produced several fatty acids of the n‐9 family, i.e. , 6,9‐ cis ‐octadecadienoic acid (18:2ω9), 8,11‐ cis ‐eicosadienoic acid (20:2ω9) and 20:3ω9. Significantly high levels of these fatty acids were produced during growth at low temperatures (12–20°C). On submerged cultivation at 20°C for 10 days in a 5‐L fermenter containing 2% glucose plus 1% yeast extract (pH 6.0), the production of 20:3ω9 reached ca. 0.8 g/L (56 mg/g dry mycelia), accounting for 15% (by wt) of the total mycelial fatty acids. The other major fatty acids were palmitic acid (6%), stearic acid (11%), oleic acid (45%), 18:2ω9 (12%) and 20:2ω9 (3%). Studies on the distribution of fatty acids among lipid classes showed that, irrespective of the growth temperature employed (12–28°C), ca. 70% (by mol) of 20:3ω9 was present in the triglyceride and the remainder in the phospholipid fraction, especially in phosphatidylcholine (PC). When the fungus was grown at 12°C, the proportion of 20:3ω9 in the PC fraction was ca. 55%.