PRODUCTION OF ODD CHAIN POLYUNSATURATED FATTY-ACIDS BY MORTIERELLA FUNGI

A soil isolate, Mortierella alpina 1S-4, was found to show high production of odd chain polyunsaturated fatty acids (PUFAs) among various arachidonic acid-producing Mortierella strains tested. The fungus mainly accumulated 5,8,11,14-cis-nonadecatetraenoic acid. With 5% n-heptadecane and 1% yeast extract as growth substrates, the amount of C19:4 acid accumulated reached 44.4 mg/g dry mycelia (0.68 mg/mL of culture broth). This value accounted for 11.2% of the total fatty acids in the extracted lipids from mycelia, and odd chain fatty acids comprised over 95% of the total mycelial fatty acids. The addition of sesamin, a specific inhibitor of DELTA-5 desaturation, caused an increase in C19:3 acid and an accompanying decrease in C19:4 acid. On the other hand, species of Mortierella that could not produce C-20 PUFAs accumulated C-17 acids, but no C-19 PUFAs, when grown with fatty substrates with an odd chain skeleton. The odd chain PUFAs were distributed in both neutral and polar lipids. The biosynthetic route to C19:4 acid was presumed to mimic the n-6 route to arachidonic acid as follows: C-17.0 --> C-17:1 --> C-17:2 --> C-17:3 --> C19:3 --> C19:4 acids.