Biosynthesis of citric and isocitric acids from ethanol by mutant Yarrowia lipolytica N 1 under continuous cultivation

The effect of ethanol, zinc, and iron (Fe2+ and Fe3+) concentration and of oxygen supply on cell growth and the production of citric acid (CA) and isocitric acid (ICA) from ethanol by mutant Yarrowia lipolytica N 1 was studied under continuous cultivation. The following peculiarities of Y. lipolytica metabolism were found: (1) intensive CA production occurred under yeast growth limitation by nitrogen; (2) inhibition of yeast growth by ethanol was accompanied by significant alterations in fatty acid composition of lipids; (3) the production of CA and ICA from ethanol required high concentrations of zinc and iron ions; (4) the intracellular iron concentration determined whether CA or ICA was predominantly formed; (5) the cell's requirement for oxygen depended on the intracellular iron concentration. The events taking place in the production of CA and ICA were evaluated through the activities of enzyme systems involved in the metabolism of ethanol and CA in this strain.