抄録
The filamentous fungus Mortierella alpina was incubated aerobically at 20 °C for two weeks with shaking in a flask containing liquid medium composed of urea, dextrose, and various minerals including KH2PO4, MgSO4·7H2O and CaCl2·2H2O. Urea was found to be as good a source of nitrogen as potato protein only when certain minerals were present in the growth medium. The potassium, phosphorus, and magnesium minerals particularly affected the growth of the fungus. The cell mass yielded was proportional to the amount of KH2PO4 present in the growth medium while only a small amount of MgSO4·7H2O was critical for the growth, although additional amounts of MgSO4·7H2O did not increase the cell mass accordingly. Under mild agitation conditions the fungus grew in pulpy form, however, magnesium sulfate pelleted the fungus in the urea medium when potassium dihydrogenphosphate was present in a KH2PO4/MgSO4·7H2O weight ratio below 1. Lipid-free cells of the uniform pellets remarkably weighed more than the pulpy form and the arachidonic acid content in fatty acids of the pellet was greater, even though the overall level of fatty acids was lower. The results suggested that the lipid-free uniform pellets consumed much glucose leaving a small amount for lipid synthesis and that in the final stage of the incubation starvation of the fungus accelerated the fatty acid conversion to produce arachidonic acid.
