[Synthesis citric and isocitric acids by Yarrowia lipolytica during yeasts growth on rapeseed oils]

The native strain Yarrowia lipolytica VKM Y-2373 grown in a complete medium exhibited the maximum lipase activity at the concentration of rapeseed oil of at least 5.0 g/l. In the course of yeast growth, no considerable changes were observed in the glycerol concentration, the proportions of the major free fatty acids formed via oil hydrolysis, or the fatty acid composition of oil. Under nitrogen limitation of cell growth, the accumulation of citric acids reached 77.1 g/l with predominance of isocitric acid at pH 6.0, whereas at pH 4.5, almost equal amounts of citric and isocitric acids were produced. Cultivation of the mutant strain Y. lipolytica N 1 at pH 4.5 resulted in the predominant accumulation of citric acid (66.6 g/l) with an insignificant amount of isocitric acid. In the period of intense acid synthesis, high production of lipase was observed.