Production of odd chain polyunsaturated fatty acids byMortierella fungi

Abstract

A soil isolate,Mortierella alpina 1S‐4, was found to show high production of odd chain polyunsaturated fatty acids (PUFAs) among various arachidonic acid‐producingMortierella strains tested. The fungus mainly accumulated 5,8,11,M‐cis‐nonadecatetraenoic acid. With 5%n‐hepta‐decane and 1% yeast extract as growth substrates, the amount of C19:4:4 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 A5 desaturation, caused an increase in C19:3 acid and an accompanying decrease in C19:4 acid. On the other hand, species ofMortierella 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: C17:0 → C17:1→ C17:2→ C17:3 → C19:3 → C19:4 acids.