Production of 5,8,11-cis-eicosatrienoic acid by a Δ12-desaturase-defective mutant ofMortierella alpina 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 reachedca. 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 wasca. 55%.