Arachidonic acid production by the oleaginous fungus Mortierella alpina 1S-4: A review

The filamentous fungus Mortierella alpina 1S-4 is capable of accumulating a large amount of triacylglycerol containing C20 polyunsaturated fatty acids (PUFAs). Indeed, triacylglycerol production by M. alpina 1S-4 can reach 20 g/L of culture broth, and the critical cellular signaling and structural PUFA arachidonic acid (ARA) comprises 30%–70% of the total fatty acid. The demonstrated health benefits of functional PUFAs have in turn encouraged the search for rich sources of these compounds, including fungal strains showing enhanced production of specific PUFAs. Screening for mutants and targeted gene manipulation of M. alpina 1S-4 have elucidated the functions of various enzymes involved in PUFA biosynthesis and established lines with improved PUFA productivity. In some cases, these strains have been used for indistrial-scale production of PUFAs, including ARA. In this review, we described practical ARA production through mutant breeding, functional analyses of genes encoding enzymes involved in PUFA biosynthesis, and recent advances in the production of specific PUFAs through molecular breeding of M. alpina 1S-4.

Lipid Fraction and Intracellular Metabolite Analysis Reveal the Mechanism of Arachidonic Acid-Rich Oil Accumulation in the Aging Process of Mortierella alpina

The mechanism of arachidonic acid (ARA) content increase during aging of Mortierella alpina was elucidated. Lipid fraction analysis showed that ARA content increased from 46.9% to 66.4% in the triacylglycerol (TAG) molecule, and ARA residue occupation increased in the majority of TAG molecules during the aging process. For the first time, intracellular metabolite analysis was conducted to reveal the pathways closely associated with ARA biosynthesis during aging. The main reason for the increased ARA content was not only at the expense of other fatty acids degradation but also at the expense of further ARA biosynthesis during aging. Furthermore, translocation played a vital role in ARA redistribution among the glycerol moiety, and mycelium did not die immediately with key pathways activated to maintain a relatively stable intracellular environment. This study lays a foundation for further improvement of ARA content in the oil product obtained from M. alpina.

Single cell oil production by Mortierella alpina

A filamentous fungus, Mortierella alpina 1S-4, was obtained, through extensive screening, as an potential producer of triacylglycerol containing C20 polyunsaturated fatty acids (PUFAs) such as arachidonic acid. With this discovery as a starting point, we conducted employing methods from metabolic engineering and molecular biology for controlling cultures and breeding mutant strains. These parental and mutant strains are now used for large-scale production of a variety of PUFAs.