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.

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The nervous system, in contrast to other tissues, is enriched in the polyunsaturated fatty acid (PUFA), arachidonic acid (ARA, 20:4 ω-6) and docosahexaenoic acid (DHA, 22:6, ω-3). Despite their abundance in the nervous system, ARA and DHA cannot be synthesized de novo by mammals, must be obtained from dietary sources and transported to the brain, thus they are termed “essential fatty acids”. It is generally accepted that PUFA is particularly important for visual system maturation and brain development during infancy. Recent findings suggest that PUFA also plays a key role in maintaining cognitive function in elderly people and that supplementing the diet with PUFA improves some neurologic disorders. The effects of PUFA on cognitive function revealed by the results of animal experiments from the view point of behavior, electrophysiology, opto-physiology, membrane-biophysics, immunohistochemistry, and biochemistry are summarized in this review.

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Recent studies suggest that arachidonic acid is useful to make taste of foods better. The addition of small amount of AA-enriched oil to vegetable oil used for cooking enhanced the umami, kokumi, aftertaste and palatability of such food as croquettes, fried rice and vegetable soup cooked with the oil. Taste of chicken meat can be improved by the amount of dietary AA supplementation. AA content in chicken meat increased linearly with increasing dietary AA content. Sensory evaluation showed that umami and kokumi of the chicken meats with high level of AA content prepared by the dietary AA supplementation scored higher than those with low level of AA. In order to consider the mechanism of AA on food palatability, some studies about effects of AA on gustatory sensation was introduced in this review. As an example, mouse behavioral studies indicated that the decomposed products from oxidized AA affected mouse taste perception to monosodium glutamate, a classic umami taste, and sucrose, a classic sweet taste, via the gustatory sensation. These studies would be useful to understand the roles of oils or fatty acid in taste of foods and be applied to development of more palatable foods.

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