The review sums up the results of studies of (1) physiological growth characteristics of the yeast Yarrowia lipolytica cultured in the presence of diverse carbon sources ( n -alkanes, glucose, and glycerol) and(2) superhigh synthesis of organic acids, which was performed at the Skryabin Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences. Microbiological processes of obtaining α -ketoglutaric, pyruvic, isocitric, and citric acids are discussed. In memoriam Aleksandr Borisovich Lozinov

The ability of yeast to synthesize alpha-ketoglutaric acid (KGA) from ethanol has been studied. Thiamine-auxotrophic yeasts of different genera and species may be able to produce KGA; the main condition of synthesis is growth limitation by thiamine. Using a model culture, mutant Yarrowia lipolytica N 1, the principal conditions affecting KGA oversynthesis were identified. These were: thiamine concentration in medium and in cells, nitrogen and oxygen concentration in medium, and pH level. A KGA concentration of 49 g/l and a yield from ethanol consumed of 42% were achieved. Based on the results of the analysis of the activities of the key enzymes participating in ethanol metabolism and KGA synthesis, a concept of the mechanism of KGA biosynthesis by Y. lipolytica yeast is suggested and discussed.

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Results of research into ethanol metabolism in yeast organisms with highly pronounced aerobic metabolism are reviewed. The low activity of NAD-dependent alcohol dehydrogenase (EC 1.1.1.1), observed under conditions of aerobic yeast growth on ethanol, demonstrates that alternative enzyme systems-alcohol oxidase (EC 1.1.3.13), microsomal ethanol-oxidizing system (including cytochrome P-450), and catalase (EC 1.11.1.6)-may be involved in the alcohol oxidation. The role of these systems in alcohol oxidation and the conditions favoring their operation in this processes are analyzed. It is concluded that iron ions are important regulators of ethanol metabolism for the microorganisms of this group.

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