Identification and production of n-8 odd-numbered polyunsaturated fatty acids by a delta12 desaturation-defective mutant of Mortierella alpina 1S-4.

A mutant of Mortierella alpina, JT-180, which is defective in its delta12 desaturase activity but exhibits enhanced activities of delta5 and delta6 desaturases, produced a high proportion (up to 80%) of odd-chain FA when grown on 3% n-heptadecane. Following growth of the mutant on n-heptadecane, three unusual odd-chain fatty acyl residues were identified as 6,9-heptadecadienoic acid (17:2), 8,11 -nonadecadienoic acid (19:2), and 5,8,11-nonadecatrienoic acid (19:3) by means of GC-MS, MS-MS, and NMR analyses. The mycelial contents of these FA reached 20.3, 3.6, and 5.8 mg/g dry mycelia, respectively, when it was cultivated in medium comprising 4% (vol/vol) n-heptadecane and 1% (wt/vol) yeast extract, pH 6.0, at 28 degrees C for 7 d. The biosynthetic route (n-8 route) to 19:3 was presumed to mimic the n-9 route to Mead acid (20:3n-9) in mammals: 17:0 --> 9-17:1 --> 6,9-17:2 --> 8,11-19:2 --> 5,8,11-19:3.