Production of Microbial Lipids Containing Arachidonic Acid and Its Related Polyunsaturated Fatty Acids

The researches of the application of functional lipids such as polyunsaturated fatty acids (PUFAs) have been conducted in various fields with a view to health and nutrition. The sources of remarkable PUFAs with more than carbon 20 were arachidonic acid from eggs and n-3 PUFAs from fish oils. The filamentous fungus Mortierella alpina 1S-4, which was found on screening of microorganisms accumulating PUFAs with more than carbon 20, produces triacylglycerols rich in arachidonic acid, i.e., ones reaching 20 g/l in concentration and containing 30-70% arachidonic acid as total fatty acids. Various mutants derived from M. alpina 1S-4 have led to the production of oils containing various PUFAs. Molecular breeding of M. alpina strains by means of manipulation of the genes involved in PUFA biosynthesis facilitates improvement of PUFA productivity and elucidation of the functions of their enzymes. This review describes practical production of arachidonic acid and its related PUFAs through mutant breeding, functional analyses of the genes of the enzymes involved in PUFA biosynthesis, and recent advances in unique PUFA production through molecular breeding.