The effect of various nitrogen sources on lipid accumulation by 17 species and strains of yeast was examined. Organic nitrogen sources resulted in considerably increased lipid contents only in strains of Lipid accumulation in CBS 14 increased from 18% (w/w), with NHCl as nitrogen source, to above 50% (w/w) when glutamate, urea or arginine was used. Stimulation of lipid production by glutamate was not observed when the yeast was grown in continuous culture with nitrogen-limiting medium. The increase in lipid content of glutamate-grown cells in batch culture was accompanied by a marked increase in the intracellular citrate concentration and its excretion from the cells. The pattern of citrate accumulation in glutamate-grown cells was mirrored by the accumulation of other metabolites, especially 2-oxoglutarate and NH ions, which were produced as a result of the increased catabolism of glutamate. It is proposed that the products of glutamate metabolism in play a major role in regulating the flux of carbon to precursors of lipid biosynthesis, such as citrate.


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