Microbiological Production of Citric and Isocitric Acids from Sunflower Oil

Svetlana V. Kamzolova*, Tatiana V. Finogenova and Igor G. Morgunov

G.K. Skryabin Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences, pr-t Nauki 5, Pushchino, RU-142290 Moscow Region, Russia

Article history:
Received June 5, 2007
Accepted September 24, 2007

Key words:
Yarrowia lipolytica, citric acid, isocitric acid, microbiological production, sunflower oil

Summary:
The growth of wild type strain Yarrowia lipolytica VKM Y-2373 and its mutant Yarrowia lipolytica N 15 as well the biosynthesis of citric and isocitric acids on sunflower oil were studied. It was indicated that cell growth was associated with the simultaneous utilization of glycerol and free fatty acids produced during oil hydrolysis. The activities of enzymes of glycerol metabolism (glycerol kinase), fatty acid assimilation enzymes of glyoxylate cycle (isocitrate lyase and malate synthase) and citric acid cycle were comparatively assayed in Y. lipolytica grown on sunflower oil, glycerol and oleic acid. Glycerol kinase and enzymes of glyoxylate cycle were active during the whole period of cell cultivation on sunflower oil. Citric acid production and a ratio between citric and isocitric acids depended on both the strain used and the medium composition. It was revealed that wild type strain Y. lipolytica VKM Y-2373 produced almost equal amounts of citric and isocitric acids at pH=4.5 and predominantly accumulated isocitric acid at pH=6.0. The mutant Y. lipolytica N 15 produced only citric acid (150 g/L with mass yield (Y_CA) of 1.32 g/g). Biochemical characteristics of mutant strain Y. lipolytica N 15 were discussed.

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