ISOLATION AND CHARACTERIZATION OF AN OMEGA-3-DESATURATION-DEFECTIVE MUTANT OF AN ARACHIDONIC ACID-PRODUCING FUNGUS, MORTIERELLA-ALPINA 1S-4

A mutant considered to be defective in the conversion of n-6 to n-3 fatty acids (omega 3-desaturation) was derived from a Delta 5-desaturation-defective mutant (Mut44) of Mortierella alpina 1S-4, after treating its spores with N-methyl-N'-nitro-N-nitrosoguanidine. This mutant cannot produce 8(Z),11(Z),14(Z),17(Z)-eicosatetraenoic acid or any other n-3 fatty acids, of which about 10% was found in its parental strain upon cultivation at 12 degrees C. The mutant's growth rate was comparable to that of the parental strain when grown at 28 degrees C, but it became much slower when the mutant grew at 12 degrees C, at which the lag phase for Mut44 was about 2 d but 5 d for the mutant.